feat: truncate short description exceeding the byte limit (#143)

* feat: truncate short description exceeding the byte limit

* fix tests

.eslintignore

@@ -0,0 +1,3 @@
+dist/
+lib/
+node_modules/

.eslintrc.json

@@ -0,0 +1,18 @@
+{
+  "env": { "node": true, "jest": true },
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": { "ecmaVersion": 9, "sourceType": "module" },
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/eslint-recommended",
+    "plugin:@typescript-eslint/recommended",
+    "plugin:import/errors",
+    "plugin:import/warnings",
+    "plugin:import/typescript",
+    "plugin:prettier/recommended"
+  ],
+  "plugins": ["@typescript-eslint"],
+  "rules": {
+    "@typescript-eslint/camelcase": "off"
+  }
+}

.github/FUNDING.yml

@@ -0,0 +1 @@
+github: peter-evans

.github/dependabot.yml

@@ -0,0 +1,21 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+    labels:
+      - "dependencies"
+
+  - package-ecosystem: "npm"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+    ignore:
+      - dependency-name: "*"
+        update-types: ["version-update:semver-major"]
+    labels:
+      - "dependencies"
+ 

.github/workflows/automerge-dependabot.yml

@@ -0,0 +1,13 @@
+name: Auto-merge Dependabot
+on: pull_request
+
+jobs:
+  automerge:
+    runs-on: ubuntu-latest
+    if: github.actor == 'dependabot[bot]'
+    steps:
+      - uses: peter-evans/enable-pull-request-automerge@v3
+        with:
+          token: ${{ secrets.ACTIONS_BOT_TOKEN }}
+          pull-request-number: ${{ github.event.pull_request.number }}
+          merge-method: squash

.github/workflows/ci.yml

@@ -0,0 +1,106 @@
+name: CI
+on:
+  push:
+    branches: [main]
+    paths-ignore:
+      - 'README.md'
+      - 'docs/**'
+  pull_request:
+    branches: [main]
+    paths-ignore:
+      - 'README.md'
+      - 'docs/**'
+
+permissions:
+  pull-requests: write
+  contents: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 16.x
+          cache: npm
+      - run: npm ci
+      - run: npm run build
+      - run: npm run format-check
+      - run: npm run lint
+      - run: npm run test
+      - uses: actions/upload-artifact@v3
+        with:
+          name: dist
+          path: dist
+      - uses: actions/upload-artifact@v3
+        with:
+          name: action.yml
+          path: action.yml
+
+  test:
+    if: github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository
+    needs: [build]
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        target: [built, committed]
+    steps:
+      - uses: actions/checkout@v3
+      - if: matrix.target == 'built' || github.event_name == 'pull_request'
+        uses: actions/download-artifact@v3
+        with:
+          name: dist
+          path: dist
+      - if: matrix.target == 'built' || github.event_name == 'pull_request'
+        uses: actions/download-artifact@v3
+        with:
+          name: action.yml
+          path: .
+
+      # Tests
+
+      - name: Prepare non-default filepath
+        run: |
+          mkdir -p some/path
+          cp README.md some/path/TEST.md
+
+      - name: Docker Hub Description (with)
+        uses: ./
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_PASSWORD }}
+          repository: peterevans/dd-ci-fixture-${{ matrix.target }}
+          short-description: ${{ matrix.target }} test fixture for dockerhub-description action
+          readme-filepath: ./some/path/TEST.md
+
+      - name: Docker Hub Description (env)
+        uses: ./
+        env:
+          DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
+          DOCKERHUB_PASSWORD: ${{ secrets.DOCKERHUB_PASSWORD }}
+          DOCKERHUB_REPOSITORY: peterevans/dd-ci-fixture-${{ matrix.target }}
+
+  package:
+    if: github.event_name == 'push' && github.ref == 'refs/heads/main'
+    needs: [test]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/download-artifact@v3
+        with:
+          name: dist
+          path: dist
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v4
+        with:
+          token: ${{ secrets.ACTIONS_BOT_TOKEN }}
+          commit-message: 'build: update distribution'
+          title: Update distribution
+          body: |
+            - Updates the distribution for changes on `main`
+
+            Auto-generated by [create-pull-request][1]
+
+            [1]: https://github.com/peter-evans/create-pull-request
+          branch: update-distribution

.github/workflows/dockerhub-description.yml

@@ -0,0 +1,27 @@
+name: Update Docker Hub Description
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+    paths:
+      - README.md
+      - .github/workflows/dockerhub-description.yml
+jobs:
+  dockerHubDescription:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Modify readme for DockerHub
+        run: |
+          sed -i 's/# Docker Hub Description/# [Docker Hub Description](https:\/\/github.com\/peter-evans\/dockerhub-description)/' README.md
+          sed -i 's/(LICENSE)/(https:\/\/github.com\/peter-evans\/dockerhub-description\/blob\/main\/LICENSE)/' README.md
+
+      - name: Docker Hub Description
+        uses: ./
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_PASSWORD }}
+          repository: peterevans/dockerhub-description
+          short-description: ${{ github.event.repository.description }}

.github/workflows/publish-docker.yml

@@ -0,0 +1,41 @@
+name: Publish Docker Image
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - v*
+env:
+  IMAGE_NAME: peterevans/dockerhub-description
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Docker Hub login
+        run: echo "${{ secrets.DOCKERHUB_PASSWORD }}" | docker login -u "${{ secrets.DOCKERHUB_USERNAME }}" --password-stdin
+
+      - name: Push image to Docker Hub
+        run: |
+          # Strip git ref prefix from version
+          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
+
+          # Strip "v" prefix from tag name
+          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+
+          # Use Docker `latest` tag convention
+          [ "$VERSION" == "main" ] && VERSION=latest
+
+          # Build and tag image
+          docker build . --file Dockerfile --tag $IMAGE_NAME --label "org.opencontainers.image.version=$VERSION"
+          docker tag $IMAGE_NAME $IMAGE_NAME:$VERSION
+
+          # Tag with the minor version if valid
+          MINOR_VERSION=$(echo $VERSION | sed -n "s/^\([0-9]*.[0-9]*\).[0-9]*$/\1/p")
+          [[ ${#MINOR_VERSION} -gt 0 ]] && docker tag $IMAGE_NAME $IMAGE_NAME:$MINOR_VERSION
+          # Tag with the major version if valid
+          MAJOR_VERSION=$(echo $VERSION | sed -n "s/^\([0-9]*\).[0-9]*.[0-9]*$/\1/p")
+          [[ ${#MAJOR_VERSION} -gt 0 ]] && docker tag $IMAGE_NAME $IMAGE_NAME:$MAJOR_VERSION
+
+          docker push $IMAGE_NAME --all-tags

.github/workflows/update-major-version.yml

@@ -0,0 +1,31 @@
+name: Update Major Version
+run-name: Update ${{ github.event.inputs.main_version }} to ${{ github.event.inputs.target }}
+
+on:
+  workflow_dispatch:
+    inputs:
+      target:
+        description: The target tag or reference
+        required: true
+      main_version:
+        type: choice
+        description: The major version tag to update
+        options:
+          - v3
+
+jobs:
+  tag:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        token: ${{ secrets.ACTIONS_BOT_TOKEN }}
+        fetch-depth: 0
+    - name: Git config
+      run: |
+        git config user.name actions-bot
+        git config user.email actions-bot@users.noreply.github.com
+    - name: Tag new target
+      run: git tag -f ${{ github.event.inputs.main_version }} ${{ github.event.inputs.target }}
+    - name: Push new tag
+      run: git push origin ${{ github.event.inputs.main_version }} --force

.gitignore

@@ -0,0 +1,2 @@
+lib/
+node_modules/

.prettierignore

@@ -0,0 +1,3 @@
+dist/
+lib/
+node_modules/

.prettierrc.json

@@ -0,0 +1,11 @@
+{
+  "printWidth": 80,
+  "tabWidth": 2,
+  "useTabs": false,
+  "semi": false,
+  "singleQuote": true,
+  "trailingComma": "none",
+  "bracketSpacing": false,
+  "arrowParens": "avoid",
+  "parser": "typescript"
+}

Dockerfile

@@ -1,15 +1,17 @@
-FROM peterevans/curl-jq:1.0.0
+FROM node:12-alpine
 
-LABEL maintainer="Peter Evans <mail@peterevans.dev>"
-LABEL repository="https://github.com/peter-evans/dockerhub-description"
-LABEL homepage="https://github.com/peter-evans/dockerhub-description"
+LABEL \
+  maintainer="Peter Evans <mail@peterevans.dev>" \
+  org.opencontainers.image.title="dockerhub-description" \
+  org.opencontainers.image.description="An action to update a Docker Hub repository description from README.md" \
+  org.opencontainers.image.authors="Peter Evans <mail@peterevans.dev>" \
+  org.opencontainers.image.url="https://github.com/peter-evans/dockerhub-description" \
+  org.opencontainers.image.vendor="https://peterevans.dev" \
+  org.opencontainers.image.licenses="MIT"
 
-LABEL com.github.actions.name="Docker Hub Description"
-LABEL com.github.actions.description="An action to update a Docker Hub repository description from README.md"
-LABEL com.github.actions.icon="upload"
-LABEL com.github.actions.color="blue"
+COPY LICENSE README.md /
 
-COPY LICENSE README.md
+COPY dist/index.js /index.js
 
 COPY entrypoint.sh /entrypoint.sh
 

README.md

@@ -1,4 +1,5 @@
 # Docker Hub Description
+[![GitHub Marketplace](https://img.shields.io/badge/Marketplace-Docker%20Hub%20Description-blue.svg?colorA=24292e&colorB=0366d6&style=flat&longCache=true&logo=data:image/png;base64,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)](https://github.com/marketplace/actions/docker-hub-description)
 
 A GitHub action to update a Docker Hub repository description from `README.md`.
 
@@ -6,68 +7,158 @@ This is useful if you `docker push` your images to Docker Hub. It provides an ea
 
 ## Usage
 
-```
-action "Update Docker Hub Repository Description" {
-  uses = "peter-evans/dockerhub-description@master"
-  secrets = ["DOCKERHUB_USERNAME", "DOCKERHUB_PASSWORD", "DOCKERHUB_REPOSITORY"]
-}
+```yml
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        repository: peterevans/dockerhub-description
 ```
 
-#### Required secrets
+### Action inputs
 
-- `DOCKERHUB_USERNAME` - Docker Hub username
-- `DOCKERHUB_PASSWORD` - Docker Hub password
-- `DOCKERHUB_REPOSITORY` - The name of the Docker Hub repository to update. (This may also be an environment variable if not considered sensitive)
+| Name | Description | Default |
+| --- | --- | --- |
+| `username` | (**required**) Docker Hub username. If updating a Docker Hub repository belonging to an organization, this user must have `Admin` permissions for the repository. | |
+| `password` | (**required**) Docker Hub password or [Personal Access Token](https://docs.docker.com/docker-hub/access-tokens/) with `read/write/delete` scope. | |
+| `repository` | Docker Hub repository in the format `<namespace>/<name>`. | `github.repository` |
+| `short-description` | Docker Hub repository short description. | |
+| `readme-filepath` | Path to the repository readme. | `./README.md` |
+| `enable-url-completion` | Enables completion of relative URLs to absolute ones. See also [known Issues](#url-completion-known-issues). | `false` |
+| `image-extensions` | File extensions that will be treated as images. | `bmp,gif,jpg,jpeg,png,svg,webp` |
 
-#### Optionally specifying the file path
+#### Content limits
+
+DockerHub has content limits.
+The readme content is limited to 25,000 bytes, and `short-description` is limited to 100 characters.
+This action truncates content to prevent the request being rejected.
+If the content has been truncated a warning will be issued in the run log.
+
+#### Specifying the file path
 
 The action assumes that there is a file called `README.md` located at the root of the repository.
-If this is not the case, the path can be overridden with an environment variable.
+If this is not the case the path can be specified with the `readme-filepath` input.
 
-```
-action "Update Docker Hub Repository Description" {
-  uses = "peter-evans/dockerhub-description@master"
-  secrets = ["DOCKERHUB_USERNAME", "DOCKERHUB_PASSWORD", "DOCKERHUB_REPOSITORY"]
-  env = {
-    README_FILEPATH = "./some-path/README.md"
-  }
-}
+```yml
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        repository: peterevans/dockerhub-description
+        readme-filepath: ./path/to/README.md
 ```
 
-#### Examples
+#### Using the GitHub repository description
 
-Updates the Docker Hub repository description whenever there is a `git push` to the `master` branch.
+The GitHub repository description can be used for the Docker Hub `short-descripton` by passing the description from the event context.
+
+```yml
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        repository: peterevans/dockerhub-description
+        short-description: ${{ github.event.repository.description }}
 ```
-workflow "New workflow" {
-  on = "push"
-  resolves = ["Update Docker Hub Repository Description"]
-}
 
-action "Filter master branch" {
-  uses = "actions/bin/filter@master"
-  args = "branch master"
-}
+### Examples
 
-action "Update Docker Hub Repository Description" {
-  needs = ["Filter master branch"]
-  uses = "peter-evans/dockerhub-description@master"
-  secrets = ["DOCKERHUB_USERNAME", "DOCKERHUB_PASSWORD", "DOCKERHUB_REPOSITORY"]
-}
+The following workflow updates the Docker Hub repository description whenever there are changes to `README.md` and the workflow file itself on the `main` branch. This workflow assumes its location to be `.github/workflows/dockerhub-description.yml`.
+
+```yml
+name: Update Docker Hub Description
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - README.md
+      - .github/workflows/dockerhub-description.yml
+jobs:
+  dockerHubDescription:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        repository: peterevans/dockerhub-description
+        short-description: ${{ github.event.repository.description }}
+        enable-url-completion: true
 ```
 
 Updates the Docker Hub repository description whenever a new release is created.
-```
-workflow "New workflow" {
-  on = "release"
-  resolves = ["Update Docker Hub Repository Description"]
-}
 
-action "Update Docker Hub Repository Description" {
-  uses = "peter-evans/dockerhub-description@master"
-  secrets = ["DOCKERHUB_USERNAME", "DOCKERHUB_PASSWORD", "DOCKERHUB_REPOSITORY"]
-}
+```yml
+name: Update Docker Hub Description
+on: release
+jobs:
+  dockerHubDescription:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Docker Hub Description
+      uses: peter-evans/dockerhub-description@v3
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_PASSWORD }}
+        repository: peterevans/dockerhub-description
+        short-description: ${{ github.event.repository.description }}
+```
+
+### URL completion known Issues
+
+The completion of relative URLs has some known issues:
+
+1. Relative markdown links in inline-code and code blocks **are also converted**:
+
+   ```markdown
+   [link in inline code](#table-of-content)
+   ```
+
+   will be converted into
+
+   ```markdown
+   [link in inline code](https://github.com/peter-evans/dockerhub-description/blob/main/./README.md#table-of-content)
+   ```
+
+2. Links containing square brackets (`]`) in the text fragment **are not converted**:
+
+   ```markdown
+   [[link text with square brackets]](#table-of-content)
+   ```
+
+3. [Reference-style links/images](https://www.markdownguide.org/basic-syntax/#reference-style-links) **are not converted**.
+
+   ```markdown
+   [table-of-content][toc]
+
+   ...
+
+   [toc]: #table-of-content "Table of content"
+   ```
+
+## Using the Docker image independently of GitHub Actions
+
+The image can be executed in other environments independently of GitHub Actions.
+Simply volume mount the location of the `README.md` file to the container and set environment variables as follows.
+
+```bash
+docker run -v $PWD:/workspace \
+  -e DOCKERHUB_USERNAME='user1' \
+  -e DOCKERHUB_PASSWORD='xxxxx' \
+  -e DOCKERHUB_REPOSITORY='user1/my-docker-image' \
+  -e README_FILEPATH='/workspace/README.md' \
+  peterevans/dockerhub-description:3
 ```
 
 ## License
 
-MIT License - see the [LICENSE](LICENSE) file for details
+[MIT](LICENSE)

__test__/readme-helper.unit.test.ts

@@ -0,0 +1,335 @@
+import {completeRelativeUrls} from '../src/readme-helper'
+
+describe('complete relative urls tests', () => {
+  const GITHUB_SERVER_URL = process.env['GITHUB_SERVER_URL']
+  const GITHUB_REPOSITORY = process.env['GITHUB_REPOSITORY']
+  const GITHUB_REF_NAME = process.env['GITHUB_REF_NAME']
+
+  const README_FILEPATH = './README.md'
+  const EXPECTED_REPOSITORY_URL = `${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}`
+  const EXPECTED_BLOB_URL = `${EXPECTED_REPOSITORY_URL}/blob/${GITHUB_REF_NAME}`
+  const EXPECTED_RAW_URL = `${EXPECTED_REPOSITORY_URL}/raw/${GITHUB_REF_NAME}`
+
+  // known issues
+  test('reference-style links/image sources are not converted', async () => {
+    const content = [
+      'table-of-content][toc]',
+      '',
+      '[toc]: #table-of-content "Table of content"'
+    ].join('\n')
+    expect(completeRelativeUrls(content, README_FILEPATH, true, '')).toEqual(
+      content
+    )
+  })
+
+  test('links containing square brackets in the text fragment are not converted', async () => {
+    expect(
+      completeRelativeUrls(
+        '[[text with square brackets]](README.md)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual('[[text with square brackets]](README.md)')
+  })
+
+  test('links containing square brackets in the text fragment are not converted', async () => {
+    expect(
+      completeRelativeUrls('`[text](README.md)`', README_FILEPATH, true, '')
+    ).toEqual(`\`[text](${EXPECTED_BLOB_URL}/README.md)\``)
+  })
+
+  // misc
+  test('do not change content when disabled', async () => {
+    expect(
+      completeRelativeUrls('[text](README.md)', README_FILEPATH, false, '')
+    ).toEqual('[text](README.md)')
+  })
+
+  test('do not change link with mailto protocol', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](mailto:mail@example.com)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](mailto:mail@example.com)`)
+  })
+
+  test('do not change link with ftp protocol', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](ftp://example.com)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](ftp://example.com)`)
+  })
+
+  test('do not change link with http protocol', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](http://example.com)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](http://example.com)`)
+  })
+
+  test('do not change link with https protocol', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](https://example.com)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](https://example.com)`)
+  })
+
+  test('do not change link with protocol-like beginning', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](abc://example.com)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](abc://example.com)`)
+  })
+
+  test('do not change image from absolute source with absolute link', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](https://example.com/image.svg)](https://example.com/image.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](https://example.com/image.svg)](https://example.com/image.svg)`
+    )
+  })
+
+  // anchors
+  test('anchor referencing the current document', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](#relative-anchor)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](${EXPECTED_BLOB_URL}/README.md#relative-anchor)`)
+  })
+
+  test('anchor referencing the current document with a title', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](#relative-anchor "the anchor (a title)")',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(
+      `[text](${EXPECTED_BLOB_URL}/README.md#relative-anchor "the anchor (a title)")`
+    )
+  })
+
+  test('anchor referencing the current document with a title and unicode', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text with 🌬](#relative-anchor "the anchor (a title with 🌬)")',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(
+      `[text with 🌬](${EXPECTED_BLOB_URL}/README.md#relative-anchor "the anchor (a title with 🌬)")`
+    )
+  })
+
+  test('anchor referencing another document', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](OTHER.md#absolute-anchor)',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(`[text](${EXPECTED_BLOB_URL}/OTHER.md#absolute-anchor)`)
+  })
+
+  test('anchor referencing another document with a title', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](OTHER.md#absolute-anchor "the anchor (a title)")',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(
+      `[text](${EXPECTED_BLOB_URL}/OTHER.md#absolute-anchor "the anchor (a title)")`
+    )
+  })
+
+  test('anchor with image referencing the current document', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](image.svg)](#absolute-anchor "the anchor (a title)")',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](${EXPECTED_RAW_URL}/image.svg)](${EXPECTED_BLOB_URL}/README.md#absolute-anchor "the anchor (a title)")`
+    )
+  })
+
+  test('anchor with image referencing another document', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](image.svg)](OTHER.md#absolute-anchor "the anchor (a title)")',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](${EXPECTED_RAW_URL}/image.svg)](${EXPECTED_BLOB_URL}/OTHER.md#absolute-anchor "the anchor (a title)")`
+    )
+  })
+
+  // documents
+  test('text document', async () => {
+    expect(
+      completeRelativeUrls('[text](document.yaml)', README_FILEPATH, true, '')
+    ).toEqual(`[text](${EXPECTED_BLOB_URL}/document.yaml)`)
+  })
+
+  test('pdf document', async () => {
+    expect(
+      completeRelativeUrls('[text](document.pdf)', README_FILEPATH, true, '')
+    ).toEqual(`[text](${EXPECTED_BLOB_URL}/document.pdf)`)
+  })
+
+  test('document with a title', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text](document.pdf "the document (a title)")',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(
+      `[text](${EXPECTED_BLOB_URL}/document.pdf "the document (a title)")`
+    )
+  })
+
+  test('document with a title and unicode', async () => {
+    expect(
+      completeRelativeUrls(
+        '[text with 🌬](document.pdf "the document (a title with 🌬)")',
+        README_FILEPATH,
+        true,
+        ''
+      )
+    ).toEqual(
+      `[text with 🌬](${EXPECTED_BLOB_URL}/document.pdf "the document (a title with 🌬)")`
+    )
+  })
+
+  // images
+  test('image with supported file extension', async () => {
+    expect(
+      completeRelativeUrls(
+        '![alttext](image.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(`![alttext](${EXPECTED_RAW_URL}/image.svg)`)
+  })
+
+  test('image with unsupported file extension', async () => {
+    expect(
+      completeRelativeUrls(
+        '![alttext](image.svg)',
+        README_FILEPATH,
+        true,
+        'jpeg'
+      )
+    ).toEqual(`![alttext](${EXPECTED_BLOB_URL}/image.svg)`)
+  })
+
+  test('image without alternate text', async () => {
+    expect(
+      completeRelativeUrls('![](image.svg)', README_FILEPATH, true, 'svg')
+    ).toEqual(`![](${EXPECTED_RAW_URL}/image.svg)`)
+  })
+
+  test('image with a title', async () => {
+    expect(
+      completeRelativeUrls(
+        '![alttext](image.svg "the image (a title)")',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(`![alttext](${EXPECTED_RAW_URL}/image.svg "the image (a title)")`)
+  })
+
+  test('image with relative link', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](image.svg)](image.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](${EXPECTED_RAW_URL}/image.svg)](${EXPECTED_BLOB_URL}/image.svg)`
+    )
+  })
+
+  test('image with a title, unicode and relative link', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext with 🌬](image.🌬.svg "the image.🌬.svg (a title)")](image.🌬.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext with 🌬](${EXPECTED_RAW_URL}/image.🌬.svg "the image.🌬.svg (a title)")](${EXPECTED_BLOB_URL}/image.🌬.svg)`
+    )
+  })
+
+  test('image from absolute source with relative link', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](https://example.com/image.svg)](image.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](https://example.com/image.svg)](${EXPECTED_BLOB_URL}/image.svg)`
+    )
+  })
+
+  test('image with absolute link', async () => {
+    expect(
+      completeRelativeUrls(
+        '[![alttext](image.svg)](https://example.com/image.svg)',
+        README_FILEPATH,
+        true,
+        'svg'
+      )
+    ).toEqual(
+      `[![alttext](${EXPECTED_RAW_URL}/image.svg)](https://example.com/image.svg)`
+    )
+  })
+})

__test__/utils.unit.test.ts

@@ -0,0 +1,10 @@
+import {truncateToBytes} from '../src/utils'
+
+describe('truncate to bytes tests', () => {
+  test('unicode aware truncation to a number of bytes', async () => {
+    expect(truncateToBytes('test string to be truncated', 10)).toEqual(
+      'test strin'
+    )
+    expect(truncateToBytes('😀😁😂🤣😃😄😅', 10)).toEqual('😀😁')
+  })
+})

action.yml

@@ -0,0 +1,34 @@
+name: 'Docker Hub Description'
+author: 'Peter Evans'
+description: 'An action to update a Docker Hub repository description from README.md'
+inputs:
+  username:
+    description: Docker Hub username
+    required: true
+  password:
+    description: Docker Hub password or Personal Access Token with read/write/delete scope
+    required: true
+  repository:
+    description: >
+      Docker Hub repository in the format `<namespace>/<name>`
+      Default: `github.repository`
+  short-description:
+    description: Docker Hub repository short description
+  readme-filepath:
+    description: >
+      Path to the repository readme
+      Default: `./README.md`
+  enable-url-completion:
+    description: >
+      Enables completion of relative URLs to absolute ones
+      Default: `false`
+  image-extensions:
+    description: >
+      File extensions that will be treated as images
+      Default: `bmp,gif,jpg,jpeg,png,svg,webp`
+runs:
+  using: 'node16'
+  main: 'dist/index.js'
+branding:
+  icon: 'upload'
+  color: 'blue'

entrypoint.sh

@@ -1,23 +1,13 @@
 #!/bin/sh -l
-set -euo pipefail
+set -eo pipefail
 IFS=$'\n\t'
 
-# Set the default path to README.md
-README_FILEPATH=${README_FILEPATH:="./README.md"}
+# Execute the action code and output to file
+node index.js > action.log 2>&1
 
-# Acquire a token for the Docker Hub API
-echo "Acquiring token"
-LOGIN_PAYLOAD="{\"username\": \"${DOCKERHUB_USERNAME}\", \"password\": \"${DOCKERHUB_PASSWORD}\"}"
-TOKEN=$(curl -s -H "Content-Type: application/json" -X POST -d ${LOGIN_PAYLOAD} https://hub.docker.com/v2/users/login/ | jq -r .token)
+# Remove lines containing sensitive information from the log
+sed -i '/::debug::/d' ./action.log
+sed -i '/::add-mask::/d' ./action.log
 
-# Send a PATCH request to update the description of the repository
-echo "Sending PATCH request"
-REPO_URL="https://hub.docker.com/v2/repositories/${DOCKERHUB_USERNAME}/${DOCKERHUB_REPOSITORY}/"
-RESPONSE_CODE=$(curl -s --write-out %{response_code} --silent --output /dev/null -H "Authorization: JWT ${TOKEN}" -X PATCH --data-urlencode full_description@${README_FILEPATH} ${REPO_URL})
-echo "Received response code: $RESPONSE_CODE"
-
-if [ $RESPONSE_CODE -eq 200 ]; then
-  exit 0
-else
-  exit 1
-fi
+# Output the log
+cat action.log

jest.config.js

@@ -0,0 +1,16 @@
+module.exports = {
+  clearMocks: true,
+  moduleFileExtensions: ['js', 'ts'],
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  testRunner: 'jest-circus/runner',
+  transform: {
+    '^.+\\.ts$': 'ts-jest'
+  },
+  verbose: true
+}
+process.env = Object.assign(process.env, {
+  GITHUB_SERVER_URL: 'https://github.com',
+  GITHUB_REPOSITORY: 'peter-evans/dockerhub-description',
+  GITHUB_REF_NAME: 'main'
+})

package.json

@@ -0,0 +1,49 @@
+{
+  "name": "dockerhub-description",
+  "version": "3.0.0",
+  "private": true,
+  "description": "An action to update a Docker Hub repository description from README.md",
+  "main": "lib/main.js",
+  "scripts": {
+    "build": "tsc && ncc build",
+    "format": "prettier --write '**/*.ts'",
+    "format-check": "prettier --check '**/*.ts'",
+    "lint": "eslint src/**/*.ts",
+    "test": "jest"
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/peter-evans/dockerhub-description.git"
+  },
+  "keywords": [
+    "actions",
+    "dockerhub",
+    "description"
+  ],
+  "author": "Peter Evans",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/peter-evans/dockerhub-description/issues"
+  },
+  "homepage": "https://github.com/peter-evans/dockerhub-description#readme",
+  "dependencies": {
+    "@actions/core": "^1.10.0",
+    "node-fetch": "^2.6.9",
+    "unicode-substring": "^0.1.0"
+  },
+  "devDependencies": {
+    "@types/jest": "^27.0.3",
+    "@types/node": "^16.18.23",
+    "@typescript-eslint/parser": "^5.57.0",
+    "@vercel/ncc": "^0.36.1",
+    "eslint": "^8.37.0",
+    "eslint-plugin-github": "^4.7.0",
+    "eslint-plugin-jest": "^25.7.0",
+    "jest": "^27.5.1",
+    "jest-circus": "^27.5.1",
+    "js-yaml": "^4.1.0",
+    "prettier": "^2.8.7",
+    "ts-jest": "^27.1.5",
+    "typescript": "^4.9.5"
+  }
+}

src/dockerhub-helper.ts

@@ -0,0 +1,51 @@
+import * as core from '@actions/core'
+import * as fetch from 'node-fetch'
+
+export async function getToken(
+  username: string,
+  password: string
+): Promise<string> {
+  const body = {
+    username: username,
+    password: password
+  }
+  const response = await fetch('https://hub.docker.com/v2/users/login', {
+    method: 'post',
+    body: JSON.stringify(body),
+    headers: {'Content-Type': 'application/json'}
+  })
+  if (!response.ok) {
+    throw new Error(
+      `Unexpected response: ${response.status} ${response.statusText}`
+    )
+  }
+  const json = await response.json()
+  core.setSecret(json['token'])
+  return json['token']
+}
+
+export async function updateRepositoryDescription(
+  token: string,
+  repository: string,
+  description: string,
+  fullDescription: string
+): Promise<void> {
+  const body = {
+    full_description: fullDescription
+  }
+  if (description) {
+    body['description'] = description
+  }
+  await fetch(`https://hub.docker.com/v2/repositories/${repository}`, {
+    method: 'patch',
+    body: JSON.stringify(body),
+    headers: {
+      'Content-Type': 'application/json',
+      Authorization: `JWT ${token}`
+    }
+  }).then(res => {
+    if (!res.ok) {
+      throw new Error(res.statusText)
+    }
+  })
+}

src/input-helper.ts

@@ -0,0 +1,94 @@
+import * as core from '@actions/core'
+import * as readmeHelper from './readme-helper'
+
+interface Inputs {
+  username: string
+  password: string
+  repository: string
+  shortDescription: string
+  readmeFilepath: string
+  enableUrlCompletion: boolean
+  imageExtensions: string
+}
+
+export function getInputs(): Inputs {
+  const inputs = {
+    username: core.getInput('username'),
+    password: core.getInput('password'),
+    repository: core.getInput('repository'),
+    shortDescription: core.getInput('short-description'),
+    readmeFilepath: core.getInput('readme-filepath'),
+    enableUrlCompletion: Boolean(core.getInput('enable-url-completion')),
+    imageExtensions: core.getInput('image-extensions')
+  }
+
+  // Environment variable input alternatives and their aliases
+
+  if (!inputs.username && process.env['DOCKERHUB_USERNAME']) {
+    inputs.username = process.env['DOCKERHUB_USERNAME']
+  }
+  if (!inputs.username && process.env['DOCKER_USERNAME']) {
+    inputs.username = process.env['DOCKER_USERNAME']
+  }
+
+  if (!inputs.password && process.env['DOCKERHUB_PASSWORD']) {
+    inputs.password = process.env['DOCKERHUB_PASSWORD']
+  }
+  if (!inputs.password && process.env['DOCKER_PASSWORD']) {
+    inputs.password = process.env['DOCKER_PASSWORD']
+  }
+
+  if (!inputs.repository && process.env['DOCKERHUB_REPOSITORY']) {
+    inputs.repository = process.env['DOCKERHUB_REPOSITORY']
+  }
+  if (!inputs.repository && process.env['DOCKER_REPOSITORY']) {
+    inputs.repository = process.env['DOCKER_REPOSITORY']
+  }
+
+  if (!inputs.shortDescription && process.env['SHORT_DESCRIPTION']) {
+    inputs.shortDescription = process.env['SHORT_DESCRIPTION']
+  }
+
+  if (!inputs.readmeFilepath && process.env['README_FILEPATH']) {
+    inputs.readmeFilepath = process.env['README_FILEPATH']
+  }
+
+  if (!inputs.enableUrlCompletion && process.env['ENABLE_URL_COMPLETION']) {
+    inputs.enableUrlCompletion = Boolean(process.env['ENABLE_URL_COMPLETION'])
+  }
+
+  if (!inputs.imageExtensions && process.env['IMAGE_EXTENSIONS']) {
+    inputs.imageExtensions = process.env['IMAGE_EXTENSIONS']
+  }
+
+  // Set defaults
+  if (!inputs.readmeFilepath) {
+    inputs.readmeFilepath = readmeHelper.README_FILEPATH_DEFAULT
+  }
+  if (!inputs.enableUrlCompletion) {
+    inputs.enableUrlCompletion = readmeHelper.ENABLE_URL_COMPLETION_DEFAULT
+  }
+  if (!inputs.imageExtensions) {
+    inputs.imageExtensions = readmeHelper.IMAGE_EXTENSIONS_DEFAULT
+  }
+  if (!inputs.repository && process.env['GITHUB_REPOSITORY']) {
+    inputs.repository = process.env['GITHUB_REPOSITORY']
+  }
+
+  // Enforce lower case, where needed
+  inputs.repository = inputs.repository.toLowerCase()
+  inputs.imageExtensions = inputs.imageExtensions.toLowerCase()
+
+  return inputs
+}
+
+function checkRequiredInput(input: string, name: string): void {
+  if (!input) {
+    throw new Error(`Required input '${name}' is missing.`)
+  }
+}
+
+export function validateInputs(inputs: Inputs): void {
+  checkRequiredInput(inputs.username, 'username')
+  checkRequiredInput(inputs.password, 'password')
+}

src/main.ts

@@ -0,0 +1,58 @@
+import * as core from '@actions/core'
+import * as inputHelper from './input-helper'
+import * as dockerhubHelper from './dockerhub-helper'
+import * as readmeHelper from './readme-helper'
+import * as utils from './utils'
+import {inspect} from 'util'
+
+const SHORT_DESCRIPTION_MAX_BYTES = 100
+
+async function run(): Promise<void> {
+  try {
+    const inputs = inputHelper.getInputs()
+    core.debug(`Inputs: ${inspect(inputs)}`)
+
+    inputHelper.validateInputs(inputs)
+
+    // Fetch the readme content
+    core.info('Reading description source file')
+    const readmeContent = await readmeHelper.getReadmeContent(
+      inputs.readmeFilepath,
+      inputs.enableUrlCompletion,
+      inputs.imageExtensions
+    )
+    core.debug(readmeContent)
+
+    // Truncate the short description if it is too long
+    const truncatedShortDescription = utils.truncateToBytes(
+      inputs.shortDescription,
+      SHORT_DESCRIPTION_MAX_BYTES
+    )
+    if (truncatedShortDescription.length !== inputs.shortDescription.length) {
+      core.warning(
+        `The short description exceeds DockerHub's limit and has been truncated to ${SHORT_DESCRIPTION_MAX_BYTES} bytes.`
+      )
+    }
+
+    // Acquire a token for the Docker Hub API
+    core.info('Acquiring token')
+    const token = await dockerhubHelper.getToken(
+      inputs.username,
+      inputs.password
+    )
+    // Send a PATCH request to update the description of the repository
+    core.info('Sending PATCH request')
+    await dockerhubHelper.updateRepositoryDescription(
+      token,
+      inputs.repository,
+      inputs.shortDescription,
+      readmeContent
+    )
+    core.info('Request successful')
+  } catch (error) {
+    core.debug(inspect(error))
+    core.setFailed(utils.getErrorMessage(error))
+  }
+}
+
+run()

src/readme-helper.ts

@@ -0,0 +1,185 @@
+import * as core from '@actions/core'
+import * as fs from 'fs'
+import * as utils from './utils'
+
+export const README_FILEPATH_DEFAULT = './README.md'
+export const IMAGE_EXTENSIONS_DEFAULT = 'bmp,gif,jpg,jpeg,png,svg,webp'
+export const ENABLE_URL_COMPLETION_DEFAULT = false
+
+const TITLE_REGEX = `(?: +"[^"]+")?`
+const REPOSITORY_URL = `${process.env['GITHUB_SERVER_URL']}/${process.env['GITHUB_REPOSITORY']}`
+const BLOB_PREFIX = `${REPOSITORY_URL}/blob/${process.env['GITHUB_REF_NAME']}/`
+const RAW_PREFIX = `${REPOSITORY_URL}/raw/${process.env['GITHUB_REF_NAME']}/`
+
+const MAX_BYTES = 25000
+
+type Rule = {
+  /**
+   * all left of the relative url belonging to the markdown image/link
+   */
+  left: RegExp
+  /**
+   * relative url
+   */
+  url: RegExp
+  /**
+   * part to prefix the relative url with (excluding github repository url)
+   */
+  absUrlPrefix: string
+}
+
+export async function getReadmeContent(
+  readmeFilepath: string,
+  enableUrlCompletion: boolean,
+  imageExtensions: string
+): Promise<string> {
+  // Fetch the readme content
+  let readmeContent = await fs.promises.readFile(readmeFilepath, {
+    encoding: 'utf8'
+  })
+
+  readmeContent = completeRelativeUrls(
+    readmeContent,
+    readmeFilepath,
+    enableUrlCompletion,
+    imageExtensions
+  )
+
+  const truncatedReadmeContent = utils.truncateToBytes(readmeContent, MAX_BYTES)
+  if (truncatedReadmeContent.length !== readmeContent.length) {
+    core.warning(
+      `The README content exceeds DockerHub's limit and has been truncated to ${MAX_BYTES} bytes.`
+    )
+  }
+
+  return truncatedReadmeContent
+}
+
+export function completeRelativeUrls(
+  readmeContent: string,
+  readmeFilepath: string,
+  enableUrlCompletion: boolean,
+  imageExtensions: string
+): string {
+  if (enableUrlCompletion) {
+    readmeFilepath = readmeFilepath.replace(/^[.][/]/, '')
+
+    // Make relative urls absolute
+    const rules = [
+      ...getRelativeReadmeAnchorsRules(readmeFilepath),
+      ...getRelativeImageUrlRules(imageExtensions),
+      ...getRelativeUrlRules()
+    ]
+
+    readmeContent = applyRules(rules, readmeContent)
+  }
+
+  return readmeContent
+}
+
+function applyRules(rules: Rule[], readmeContent: string): string {
+  rules.forEach(rule => {
+    const combinedRegex = `${rule.left.source}[(]${rule.url.source}[)]`
+    core.debug(`rule: ${combinedRegex}`)
+
+    const replacement = `$<left>(${rule.absUrlPrefix}$<url>)`
+    core.debug(`replacement: ${replacement}`)
+
+    readmeContent = readmeContent.replace(
+      new RegExp(combinedRegex, 'giu'),
+      replacement
+    )
+  })
+
+  return readmeContent
+}
+
+// has to be applied first to avoid wrong results
+function getRelativeReadmeAnchorsRules(readmeFilepath: string): Rule[] {
+  const prefix = `${BLOB_PREFIX}${readmeFilepath}`
+
+  // matches e.g.:
+  //    #table-of-content
+  //    #table-of-content "the anchor (a title)"
+  const url = new RegExp(`(?<url>#[^)]+${TITLE_REGEX})`)
+
+  const rules: Rule[] = [
+    // matches e.g.:
+    //    [#table-of-content](#table-of-content)
+    //    [#table-of-content](#table-of-content "the anchor (a title)")
+    {
+      left: /(?<left>\[[^\]]+\])/,
+      url: url,
+      absUrlPrefix: prefix
+    },
+
+    // matches e.g.:
+    //    [![media/image.svg](media/image.svg)](#table-of-content)
+    //    [![media/image.svg](media/image.svg "title a")](#table-of-content "title b")
+    {
+      left: /(?<left>\[!\[[^\]]*\]\([^)]+\)\])/,
+      url: url,
+      absUrlPrefix: prefix
+    }
+  ]
+
+  return rules
+}
+
+function getRelativeImageUrlRules(imageExtensions: string): Rule[] {
+  const extensionsRegex = imageExtensions.replace(/,/g, '|')
+  // matches e.g.:
+  //    media/image.svg
+  //    media/image.svg "with title"
+  const url = new RegExp(
+    `(?<url>[^:)]+[.](?:${extensionsRegex})${TITLE_REGEX})`
+  )
+
+  const rules: Rule[] = [
+    // matches e.g.:
+    //    ![media/image.svg](media/image.svg)
+    //    ![media/image.svg](media/image.svg "with title")
+    {
+      left: /(?<left>!\[[^\]]*\])/,
+      url: url,
+      absUrlPrefix: RAW_PREFIX
+    }
+  ]
+
+  return rules
+}
+
+function getRelativeUrlRules(): Rule[] {
+  // matches e.g.:
+  //    .releaserc.yaml
+  //    README.md#table-of-content "title b"
+  //    .releaserc.yaml "the .releaserc.yaml file (a title)"
+  const url = new RegExp(`(?<url>[^:)]+${TITLE_REGEX})`)
+
+  const rules: Rule[] = [
+    // matches e.g.:
+    //    [.releaserc.yaml](.releaserc.yaml)
+    //    [.releaserc.yaml](.releaserc.yaml "the .releaserc.yaml file (a title)")
+    {
+      left: /(?<left>\[[^\]]+\])/,
+      url: url,
+      absUrlPrefix: BLOB_PREFIX
+    },
+
+    // matches e.g.:
+    //    [![media/image.svg](media/image.svg)](media/image.svg)
+    //    [![media/image.svg](media/image.svg)](README.md#table-of-content "title b")
+    //    [![media/image.svg](media/image.svg "title a")](media/image.svg)
+    //    [![media/image.svg](media/image.svg "title a")](media/image.svg "title b")
+    //    [![media/image.svg](media/image.svg "title a")](README.md#table-of-content "title b")
+    {
+      left: new RegExp(
+        `(?<left>\\[!\\[[^\\]]*\\]\\([^)]+${TITLE_REGEX}\\)\\])`
+      ),
+      url: url,
+      absUrlPrefix: BLOB_PREFIX
+    }
+  ]
+
+  return rules
+}

src/utils.ts

@@ -0,0 +1,14 @@
+import unicodeSubstring = require('unicode-substring')
+
+export function getErrorMessage(error: unknown) {
+  if (error instanceof Error) return error.message
+  return String(error)
+}
+
+export function truncateToBytes(s: string, n: number): string {
+  let len = n
+  while (Buffer.byteLength(s) > n) {
+    s = unicodeSubstring(s, 0, len--)
+  }
+  return s
+}

tsconfig.json

@@ -0,0 +1,16 @@
+{
+  "compilerOptions": {
+    "target": "es6",
+    "module": "commonjs",
+    "lib": [
+      "es6"
+    ],
+    "outDir": "./lib",
+    "rootDir": "./src",
+    "declaration": true,
+    "strict": true,
+    "noImplicitAny": false,
+    "esModuleInterop": true
+  },
+  "exclude": ["__test__", "lib", "node_modules"]
+}