feat: convert relative urls to absolute (#125) (#126)

* feat: convert relative urls to absolute

* test: add tests for conversion of relative urls

Co-authored-by: Marty Winkler <mrtwnklr@users.noreply.github.com>

README.md

@@ -25,6 +25,8 @@ This is useful if you `docker push` your images to Docker Hub. It provides an ea
 | `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](#known-issues). | `false` |
+| `image-extensions` | File extensions that will be treated as images. | `bmp,gif,jpg,jpeg,png,svg,webp` |
 
 #### Content limits
 
@@ -86,6 +88,7 @@ jobs:
         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.
@@ -122,6 +125,38 @@ docker run -v $PWD:/workspace \
   peterevans/dockerhub-description:3
 ```
 
+## 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"
+   ```
+
 ## License
 
 [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)`
+    )
+  })
+})

action.yml

@@ -18,6 +18,14 @@ inputs:
     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: >
+      Extensions of files that you be treated as images
+      Default: `bmp,gif,jpg,jpeg,png,svg,webp`
 runs:
   using: 'node16'
   main: 'dist/index.js'

dist/index.js

@@ -121,14 +121,16 @@ var __importStar = (this && this.__importStar) || function (mod) {
 Object.defineProperty(exports, "__esModule", ({ value: true }));
 exports.validateInputs = exports.getInputs = void 0;
 const core = __importStar(__nccwpck_require__(2186));
-const README_FILEPATH_DEFAULT = './README.md';
+const readmeHelper = __importStar(__nccwpck_require__(3367));
 function getInputs() {
     const inputs = {
         username: core.getInput('username'),
         password: core.getInput('password'),
         repository: core.getInput('repository'),
         shortDescription: core.getInput('short-description'),
-        readmeFilepath: core.getInput('readme-filepath')
+        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']) {
@@ -155,15 +157,28 @@ function getInputs() {
     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 = README_FILEPATH_DEFAULT;
+        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'];
     }
-    // Docker repositories must be all lower case
+    // Enforce lower case, where needed
     inputs.repository = inputs.repository.toLowerCase();
+    inputs.imageExtensions = inputs.imageExtensions.toLowerCase();
     return inputs;
 }
 exports.getInputs = getInputs;
@@ -222,7 +237,7 @@ Object.defineProperty(exports, "__esModule", ({ value: true }));
 const core = __importStar(__nccwpck_require__(2186));
 const inputHelper = __importStar(__nccwpck_require__(5480));
 const dockerhubHelper = __importStar(__nccwpck_require__(1812));
-const fs = __importStar(__nccwpck_require__(7147));
+const readmeHelper = __importStar(__nccwpck_require__(3367));
 const util_1 = __nccwpck_require__(3837);
 function getErrorMessage(error) {
     if (error instanceof Error)
@@ -236,9 +251,9 @@ function run() {
             core.debug(`Inputs: ${(0, util_1.inspect)(inputs)}`);
             inputHelper.validateInputs(inputs);
             // Fetch the readme content
-            const readmeContent = yield fs.promises.readFile(inputs.readmeFilepath, {
+            core.info('Reading description source file');
-                encoding: 'utf8'
+            const readmeContent = yield readmeHelper.getReadmeContent(inputs.readmeFilepath, inputs.enableUrlCompletion, inputs.imageExtensions);
-            });
+            core.debug(readmeContent);
             // Acquire a token for the Docker Hub API
             core.info('Acquiring token');
             const token = yield dockerhubHelper.getToken(inputs.username, inputs.password);
@@ -256,6 +271,167 @@ function run() {
 run();
 
 
+/***/ }),
+
+/***/ 3367:
+/***/ (function(__unused_webpack_module, exports, __nccwpck_require__) {
+
+"use strict";
+
+var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
+    if (k2 === undefined) k2 = k;
+    var desc = Object.getOwnPropertyDescriptor(m, k);
+    if (!desc || ("get" in desc ? !m.__esModule : desc.writable || desc.configurable)) {
+      desc = { enumerable: true, get: function() { return m[k]; } };
+    }
+    Object.defineProperty(o, k2, desc);
+}) : (function(o, m, k, k2) {
+    if (k2 === undefined) k2 = k;
+    o[k2] = m[k];
+}));
+var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
+    Object.defineProperty(o, "default", { enumerable: true, value: v });
+}) : function(o, v) {
+    o["default"] = v;
+});
+var __importStar = (this && this.__importStar) || function (mod) {
+    if (mod && mod.__esModule) return mod;
+    var result = {};
+    if (mod != null) for (var k in mod) if (k !== "default" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
+    __setModuleDefault(result, mod);
+    return result;
+};
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+Object.defineProperty(exports, "__esModule", ({ value: true }));
+exports.completeRelativeUrls = exports.getReadmeContent = exports.ENABLE_URL_COMPLETION_DEFAULT = exports.IMAGE_EXTENSIONS_DEFAULT = exports.README_FILEPATH_DEFAULT = void 0;
+const core = __importStar(__nccwpck_require__(2186));
+const fs = __importStar(__nccwpck_require__(7147));
+exports.README_FILEPATH_DEFAULT = './README.md';
+exports.IMAGE_EXTENSIONS_DEFAULT = 'bmp,gif,jpg,jpeg,png,svg,webp';
+exports.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']}/`;
+function getReadmeContent(readmeFilepath, enableUrlCompletion, imageExtensions) {
+    return __awaiter(this, void 0, void 0, function* () {
+        // Fetch the readme content
+        let readmeContent = yield fs.promises.readFile(readmeFilepath, {
+            encoding: 'utf8'
+        });
+        readmeContent = completeRelativeUrls(readmeContent, readmeFilepath, enableUrlCompletion, imageExtensions);
+        return readmeContent;
+    });
+}
+exports.getReadmeContent = getReadmeContent;
+function completeRelativeUrls(readmeContent, readmeFilepath, enableUrlCompletion, imageExtensions) {
+    if (enableUrlCompletion) {
+        readmeFilepath = readmeFilepath.replace(/^[.][/]/, '');
+        // Make relative urls absolute
+        const rules = [
+            ...getRelativeReadmeAnchorsRules(readmeFilepath),
+            ...getRelativeImageUrlRules(imageExtensions),
+            ...getRelativeUrlRules()
+        ];
+        readmeContent = applyRules(rules, readmeContent);
+    }
+    return readmeContent;
+}
+exports.completeRelativeUrls = completeRelativeUrls;
+function applyRules(rules, readmeContent) {
+    rules.forEach(rule => {
+        const combinedRegex = `${rule.left.source}[(]${rule.url.source}[)]`;
+        core.debug(`rule: ${combinedRegex}`);
+        const replacement = `$<left>(${rule.absUrlPrefix}$<url>)`;
+        core.debug(`replacement: ${replacement}`);
+        readmeContent = readmeContent.replace(new RegExp(combinedRegex, 'giu'), replacement);
+    });
+    return readmeContent;
+}
+// has to be applied first to avoid wrong results
+function getRelativeReadmeAnchorsRules(readmeFilepath) {
+    const prefix = `${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 = [
+        // 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) {
+    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 = [
+        // 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() {
+    // 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 = [
+        // 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;
+}
+
+
 /***/ }),
 
 /***/ 7351:

jest.config.js

@@ -9,3 +9,8 @@ module.exports = {
   },
   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

@@ -9,7 +9,7 @@
     "format": "prettier --write '**/*.ts'",
     "format-check": "prettier --check '**/*.ts'",
     "lint": "eslint src/**/*.ts",
-    "test": "jest --passWithNoTests"
+    "test": "jest"
   },
   "repository": {
     "type": "git",

src/input-helper.ts

@@ -1,6 +1,5 @@
 import * as core from '@actions/core'
-
+import * as readmeHelper from './readme-helper'
-const README_FILEPATH_DEFAULT = './README.md'
 
 interface Inputs {
   username: string
@@ -8,6 +7,8 @@ interface Inputs {
   repository: string
   shortDescription: string
   readmeFilepath: string
+  enableUrlCompletion: boolean
+  imageExtensions: string
 }
 
 export function getInputs(): Inputs {
@@ -16,7 +17,9 @@ export function getInputs(): Inputs {
     password: core.getInput('password'),
     repository: core.getInput('repository'),
     shortDescription: core.getInput('short-description'),
-    readmeFilepath: core.getInput('readme-filepath')
+    readmeFilepath: core.getInput('readme-filepath'),
+    enableUrlCompletion: Boolean(core.getInput('enable-url-completion')),
+    imageExtensions: core.getInput('image-extensions')
   }
 
   // Environment variable input alternatives and their aliases
@@ -50,16 +53,31 @@ export function getInputs(): Inputs {
     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 = README_FILEPATH_DEFAULT
+    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']
   }
 
-  // Docker repositories must be all lower case
+  // Enforce lower case, where needed
   inputs.repository = inputs.repository.toLowerCase()
+  inputs.imageExtensions = inputs.imageExtensions.toLowerCase()
 
   return inputs
 }

src/main.ts

@@ -1,7 +1,7 @@
 import * as core from '@actions/core'
 import * as inputHelper from './input-helper'
 import * as dockerhubHelper from './dockerhub-helper'
-import * as fs from 'fs'
+import * as readmeHelper from './readme-helper'
 import {inspect} from 'util'
 
 function getErrorMessage(error: unknown) {
@@ -17,9 +17,13 @@ async function run(): Promise<void> {
     inputHelper.validateInputs(inputs)
 
     // Fetch the readme content
-    const readmeContent = await fs.promises.readFile(inputs.readmeFilepath, {
+    core.info('Reading description source file')
-      encoding: 'utf8'
+    const readmeContent = await readmeHelper.getReadmeContent(
-    })
+      inputs.readmeFilepath,
+      inputs.enableUrlCompletion,
+      inputs.imageExtensions
+    )
+    core.debug(readmeContent)
 
     // Acquire a token for the Docker Hub API
     core.info('Acquiring token')

src/readme-helper.ts

@@ -0,0 +1,175 @@
+import * as core from '@actions/core'
+import * as fs from 'fs'
+
+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']}/`
+
+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
+  )
+
+  return readmeContent
+}
+
+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
+}