feat: add root_path config option (#14)

Fixes #12

.markdownlint-cli2.mjs

@@ -4,7 +4,9 @@ const config = {
   config: {
     extends: "markdownlint/style/prettier",
     default: true,
-    "relative-links": true,
+    "relative-links": {
+      root_path: ".",
+    },
     "no-inline-html": false,
   },
   globs: ["**/*.md"],

CONTRIBUTING.md

@@ -4,7 +4,7 @@ Thanks a lot for your interest in contributing to **markdownlint-rule-relative-l
 
 ## Code of Conduct
 
-**markdownlint-rule-relative-links** adopted the [Contributor Covenant](https://www.contributor-covenant.org/) as its Code of Conduct, and we expect project participants to adhere to it. Please read [the full text](./CODE_OF_CONDUCT.md) so that you can understand what actions will and will not be tolerated.
+**markdownlint-rule-relative-links** adopted the [Contributor Covenant](https://www.contributor-covenant.org/) as its Code of Conduct, and we expect project participants to adhere to it. Please read [the full text](/CODE_OF_CONDUCT.md) so that you can understand what actions will and will not be tolerated.
 
 ## Open Development
 

README.md

@@ -51,12 +51,13 @@ awesome.md:3 relative-links Relative links should be valid ["./invalid.txt" shou
 - Support images (e.g: `![Image](./image.png)`).
 - Support links fragments similar to the [built-in `markdownlint` rule - MD051](https://github.com/DavidAnson/markdownlint/blob/main/doc/md051.md) (e.g: `[Link](./awesome.md#heading)`).
 - Ignore external links and absolute paths as it only checks relative links (e.g: `https://example.com/` or `/absolute/path.png`).
+- If necessary, absolute paths can be validated too, with [`root_path` configuration option](#absolute-paths).
 
 ### Limitations
 
 - Only images and links defined using markdown syntax are validated, html syntax is ignored (e.g: `<a href="./link.txt" />` or `<img src="./image.png" />`).
 
-Contributions are welcome to improve the rule, and to alleviate these limitations. See [CONTRIBUTING.md](./CONTRIBUTING.md) for more information.
+Contributions are welcome to improve the rule, and to alleviate these limitations. See [CONTRIBUTING.md](/CONTRIBUTING.md) for more information.
 
 ### Related links
 
@@ -108,6 +109,25 @@ export default config
 }
 ```
 
+### Absolute paths
+
+GitHub (and, likely, other similar platforms) resolves absolute paths in Markdown links relative to the repository root.
+
+To validate such links, add `root_path` option to the configuration:
+
+```js
+  config: {
+    default: true,
+    "relative-links": {
+      root_path: ".",
+    },
+  },
+```
+
+After this change, all absolute paths will be converted to relative paths, and will be resolved relative to the specified directory.
+
+For example, if you run markdownlint from a subdirectory (if `package.json` is located in a subdirectory), you should set `root_path` to `".."`.
+
 ## Usage
 
 ```sh
@@ -118,8 +138,8 @@ node --run lint:markdown
 
 Anyone can help to improve the project, submit a Feature Request, a bug report or even correct a simple spelling mistake.
 
-The steps to contribute can be found in the [CONTRIBUTING.md](./CONTRIBUTING.md) file.
+The steps to contribute can be found in the [CONTRIBUTING.md](/CONTRIBUTING.md) file.
 
 ## 📄 License
 
-[MIT](./LICENSE)
+[MIT](/LICENSE)

src/index.js

@@ -51,17 +51,25 @@ const relativeLinksRule = {
           }
         }
 
-        if (hrefSrc == null) {
+        if (hrefSrc == null || hrefSrc.startsWith("#")) {
           continue
         }
 
-        const url = new URL(hrefSrc, pathToFileURL(params.name))
-        const isRelative =
-          url.protocol === "file:" &&
-          !hrefSrc.startsWith("/") &&
-          !hrefSrc.startsWith("#")
+        let url
 
-        if (!isRelative) {
+        if (hrefSrc.startsWith("/")) {
+          const rootPath = params.config["root_path"]
+
+          if (!rootPath) {
+            continue
+          }
+
+          url = new URL(`.${hrefSrc}`, pathToFileURL(`${rootPath}/`))
+        } else {
+          url = new URL(hrefSrc, pathToFileURL(params.name))
+        }
+
+        if (url.protocol !== "file:") {
           continue
         }
 

test/fixtures/config-dependent/absolute-paths.md

@@ -0,0 +1,3 @@
+# Valid
+
+![Absolute Path](/test/fixtures/image.png)

test/index.test.js

@@ -5,17 +5,22 @@ import * as markdownlint from "markdownlint/promise"
 
 import relativeLinksRule, { markdownIt } from "../src/index.js"
 
+const defaultConfig = {
+  "relative-links": true,
+}
+
 /**
  *
  * @param {string} fixtureFile
+ * @param {Object} config
  * @returns
  */
-const validateMarkdownLint = async (fixtureFile) => {
+const validateMarkdownLint = async (fixtureFile, config = defaultConfig) => {
   const lintResults = await markdownlint.lint({
     files: [fixtureFile],
     config: {
       default: false,
-      "relative-links": true,
+      ...config,
     },
     customRules: [relativeLinksRule],
     markdownItFactory: () => {
@@ -146,11 +151,27 @@ test("ensure the rule validates correctly", async (t) => {
         fixturePath: "test/fixtures/invalid/non-existing-image.md",
         errors: ['"./image.png" should exist in the file system'],
       },
+      {
+        name: "should be invalid with incorrect absolute paths",
+        fixturePath: "test/fixtures/config-dependent/absolute-paths.md",
+        errors: ['"/test/fixtures/image.png" should exist in the file system'],
+        config: {
+          "relative-links": {
+            root_path: "test",
+          },
+        },
+      },
     ]
 
-    for (const { name, fixturePath, errors } of testCases) {
+    for (const {
+      name,
+      fixturePath,
+      errors,
+      config = defaultConfig,
+    } of testCases) {
       await t.test(name, async () => {
-        const lintResults = (await validateMarkdownLint(fixturePath)) ?? []
+        const lintResults =
+          (await validateMarkdownLint(fixturePath, config)) ?? []
         const errorsDetails = lintResults.map((result) => {
           assert.deepEqual(result.ruleNames, relativeLinksRule.names)
           assert.deepEqual(
@@ -219,7 +240,7 @@ test("ensure the rule validates correctly", async (t) => {
         fixturePath: "test/fixtures/valid/existing-image.md",
       },
       {
-        name: "should ignore absolute paths",
+        name: "should ignore absolute paths if root_path is not set",
         fixturePath: "test/fixtures/valid/ignore-absolute-paths.md",
       },
       {
@@ -231,11 +252,21 @@ test("ensure the rule validates correctly", async (t) => {
         fixturePath:
           "test/fixtures/valid/ignore-fragment-checking-in-own-file.md",
       },
+      {
+        name: "should be valid with correct absolute paths if root_path is set",
+        fixturePath: "test/fixtures/config-dependent/absolute-paths.md",
+        config: {
+          "relative-links": {
+            root_path: ".",
+          },
+        },
+      },
     ]
 
-    for (const { name, fixturePath } of testCases) {
+    for (const { name, fixturePath, config = defaultConfig } of testCases) {
       await t.test(name, async () => {
-        const lintResults = (await validateMarkdownLint(fixturePath)) ?? []
+        const lintResults =
+          (await validateMarkdownLint(fixturePath, config)) ?? []
         const errorsDetails = lintResults.map((result) => {
           return result.errorDetail
         })