fix: only detect file: protocol links

fixes #1

README.md

@@ -4,15 +4,13 @@
   <strong>Custom rule for <a href="https://github.com/DavidAnson/markdownlint">markdownlint</a> to validate relative links.</strong>
 </p>
 
-</p>
-
 <p align="center">
   <a href="./CONTRIBUTING.md"><img src="https://img.shields.io/badge/PRs-welcome-brightgreen.svg?style=flat" /></a>
   <a href="./LICENSE"><img src="https://img.shields.io/badge/licence-MIT-blue.svg" alt="Licence MIT"/></a>
   <a href="./CODE_OF_CONDUCT.md"><img src="https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg" alt="Contributor Covenant" /></a>
   <br />
   <a href="https://github.com/Divlo/markdownlint-rule-relative-links/actions/workflows/lint.yml"><img src="https://github.com/Divlo/markdownlint-rule-relative-links/actions/workflows/lint.yml/badge.svg?branch=develop" /></a>
-  <a href="https://github.com/Divlo/emarkdownlint-rule-relative-linksactions/workflows/test.yml"><img src="https://github.com/Divlo/markdownlint-rule-relative-links/actions/workflows/test.yml/badge.svg?branch=develop" /></a>
+  <a href="https://github.com/Divlo/markdownlint-rule-relative-linksactions/workflows/test.yml"><img src="https://github.com/Divlo/markdownlint-rule-relative-links/actions/workflows/test.yml/badge.svg?branch=develop" /></a>
   <br />
   <a href="https://conventionalcommits.org"><img src="https://img.shields.io/badge/Conventional%20Commits-1.0.0-yellow.svg" alt="Conventional Commits" /></a>
   <a href="https://github.com/semantic-release/semantic-release"><img src="https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg" alt="semantic-release" /></a>
@@ -23,9 +21,32 @@
 
 **markdownlint-rule-relative-links** is a [markdownlint](https://github.com/DavidAnson/markdownlint) custom rule to validate relative links.
 
-It ensures that relative links that start with `./` or `../` (or not starting with external protocols like `http://` or `https://`) are working and not "dead" which means that it exists in the file system of the project that uses `markdownlint`.
+It ensures that relative links (using `file:` protocol) are working and not "dead" which means that it exists in the file system of the project that uses `markdownlint`.
 
-Related links:
+### Example
+
+File structure:
+
+```txt
+├── abc.txt
+└── awesome.md
+```
+
+With `awesome.md` content:
+
+```md
+[abc](./abc.txt)
+
+[Dead link](./dead.txt)
+```
+
+Running `markdownlint-cli2` with `markdownlint-rule-relative-links` will output:
+
+```sh
+awesome.md:3 relative-links Relative links should be valid [Link "./dead.txt" is dead]
+```
+
+### Related links
 
 - [DavidAnson/markdownlint#253](https://github.com/DavidAnson/markdownlint/issues/253)
 - [DavidAnson/markdownlint#121](https://github.com/DavidAnson/markdownlint/issues/121)

src/index.js

@@ -40,14 +40,6 @@ const addError = (onError, lineNumber, detail, context, range, fixInfo) => {
   })
 }
 
-const EXTERNAL_PROTOCOLS = new Set([
-  'http:',
-  'https:',
-  'mailto:',
-  'tel:',
-  'ftp:'
-])
-
 const customRule = {
   names: ['relative-links'],
   description: 'Relative links should be valid',
@@ -56,23 +48,35 @@ const customRule = {
     filterTokens(params, 'inline', (token) => {
       token.children.forEach((child) => {
         const { lineNumber, type, attrs } = child
+
+        /** @type {string | null} */
+        let hrefSrc = null
+
         if (type === 'link_open') {
           attrs.forEach((attr) => {
             if (attr[0] === 'href') {
-              const href = attr[1]
-              const url = new URL(href, pathToFileURL(params.name))
-              url.hash = ''
-              const isRelative =
-                href.startsWith('./') ||
-                href.startsWith('../') ||
-                !EXTERNAL_PROTOCOLS.has(url.protocol)
-              if (isRelative && !fs.existsSync(url.pathname)) {
-                const detail = `Link "${href}" is dead`
-                addError(onError, lineNumber, detail)
-              }
+              hrefSrc = attr[1]
             }
           })
         }
+
+        if (type === 'image') {
+          attrs.forEach((attr) => {
+            if (attr[0] === 'src') {
+              hrefSrc = attr[1]
+            }
+          })
+        }
+
+        if (hrefSrc != null) {
+          const url = new URL(hrefSrc, pathToFileURL(params.name))
+          url.hash = ''
+          const isRelative = url.protocol === 'file:'
+          if (isRelative && !fs.existsSync(url)) {
+            const detail = `Link "${hrefSrc}" is dead`
+            addError(onError, lineNumber, detail)
+          }
+        }
       })
     })
   }

test/basic.test.js

@@ -12,13 +12,23 @@ tap.test('ensure we validate correctly', async (t) => {
     customRules: [relativeLinks]
   })
   t.equal(lintResults['test/fixtures/Valid.md'].length, 0)
-  t.equal(lintResults['test/fixtures/Invalid.md'].length, 1)
+  t.equal(lintResults['test/fixtures/Invalid.md'].length, 2)
+
   t.equal(
-    lintResults['test/fixtures/Invalid.md'][0].ruleDescription,
+    lintResults['test/fixtures/Invalid.md'][0]?.ruleDescription,
     'Relative links should be valid'
   )
   t.equal(
-    lintResults['test/fixtures/Invalid.md'][0].errorDetail,
+    lintResults['test/fixtures/Invalid.md'][0]?.errorDetail,
     'Link "./basic.test.js" is dead'
   )
+
+  t.equal(
+    lintResults['test/fixtures/Invalid.md'][1]?.ruleDescription,
+    'Relative links should be valid'
+  )
+  t.equal(
+    lintResults['test/fixtures/Invalid.md'][1]?.errorDetail,
+    'Link "../image.png" is dead'
+  )
 })

test/fixtures/Invalid.md

@@ -1,3 +1,5 @@
 # Invalid
 
 [basic.js](./basic.test.js)
+
+![Image](../image.png)

test/fixtures/Valid.md

@@ -1,3 +1,11 @@
 # Valid
 
 [basic.js](../basic.test.js)
+
+![Image](./image.png)
+
+[External https link](https://example.com/)
+
+[External https link 2](https:./external.https)
+
+[External ftp link](ftp:./external.ftp)