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feat: create no-duplicate-definitions (#360)
* feat: create `no-duplicate-definitions` * wip: complete rule definition * wip: update `README.md` * wip: add more testcases * wip: rename `ignores` to `ignore` * wip: add support for `FootnoteDefinition` * wip: add more testcases * wip: update docs * wip: docs * wip: refactor code * wip: address reviews * wip: address reviews by snitin315 * wip: address reviews by fasttime * wip: fix typos * wip: refactor logics * wip: use Set
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‎README.md‎

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@@ -75,6 +75,7 @@ export default defineConfig([
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| :- | :- | :-: |
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| [`fenced-code-language`](./docs/rules/fenced-code-language.md) | Require languages for fenced code blocks | yes |
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| [`heading-increment`](./docs/rules/heading-increment.md) | Enforce heading levels increment by one | yes |
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| [`no-duplicate-definitions`](./docs/rules/no-duplicate-definitions.md) | Disallow duplicate definitions | yes |
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| [`no-duplicate-headings`](./docs/rules/no-duplicate-headings.md) | Disallow duplicate headings in the same document | no |
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| [`no-empty-definitions`](./docs/rules/no-empty-definitions.md) | Disallow empty definitions | yes |
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| [`no-empty-images`](./docs/rules/no-empty-images.md) | Disallow empty images | yes |

‎docs/rules/no-duplicate-definitions.md‎

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# no-duplicate-definitions
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Disallow duplicate definitions.
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## Background
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In Markdown, it's possible to define the same definition identifier multiple times. However, this is usually a mistake, as it can lead to unintended or incorrect link, image, and footnote references.
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Please note that this rule does not report definition-style comments. For example:
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```markdown
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[//]: # (This is a comment 1)
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[//]: <> (This is a comment 2)
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```
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## Rule Details
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> [!IMPORTANT] <!-- eslint-disable-line -- This should be fixed in https://github.com/eslint/markdown/issues/294 -->
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>
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> The `FootnoteDefinition` node is detected only when using `language` mode [`markdown/gfm`](/README.md#languages).
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This rule warns when `Definition` and `FootnoteDefinition` type identifiers are defined multiple times. Please note that this rule is **case-insensitive**, meaning `earth` and `Earth` are treated as the same identifier.
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Examples of **incorrect** code:
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```markdown
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<!-- eslint markdown/no-duplicate-definitions: "error" -->
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<!-- definition -->
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[mercury]: https://example.com/mercury/
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[mercury]: https://example.com/venus/
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[earth]: https://example.com/earth/
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[Earth]: https://example.com/mars/
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<!-- footnote definition -->
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[^mercury]: Hello, Mercury!
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[^mercury]: Hello, Venus!
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[^earth]: Hello, Earth!
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[^Earth]: Hello, Mars!
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```
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Examples of **correct** code:
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```markdown
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<!-- eslint markdown/no-duplicate-definitions: "error" -->
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<!-- definition -->
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[mercury]: https://example.com/mercury/
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[venus]: https://example.com/venus/
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<!-- footnote definition -->
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[^mercury]: Hello, Mercury!
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[^venus]: Hello, Venus!
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<!-- definition-style comment -->
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[//]: # (This is a comment 1)
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[//]: <> (This is a comment 2)
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```
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## Options
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The following options are available on this rule:
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- `allowDefinitions: Array<string>` - when specified, duplicate definitions are allowed if they match one of the identifiers in this array. This is useful for ignoring definitions that are intentionally duplicated. (default: `["//"]`)
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Examples of **correct** code when configured as `"no-duplicate-definitions: ["error", { allowDefinitions: ["mercury"] }]`:
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```markdown
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<!-- eslint markdown/no-duplicate-definitions: ["error", { allowDefinitions: ["mercury"] }] -->
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[mercury]: https://example.com/mercury/
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[mercury]: https://example.com/venus/
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```
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- `allowFootnoteDefinitions: Array<string>` - when specified, duplicate footnote definitions are allowed if they match one of the identifiers in this array. This is useful for ignoring footnote definitions that are intentionally duplicated. (default: `[]`)
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Examples of **correct** code when configured as `"no-duplicate-definitions: ["error", { allowFootnoteDefinitions: ["mercury"] }]`:
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```markdown
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<!-- eslint markdown/no-duplicate-definitions: ["error", { allowFootnoteDefinitions: ["mercury"] }] -->
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[^mercury]: Hello, Mercury!
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[^mercury]: Hello, Venus!
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```
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## When Not to Use It
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If you are using a different style of definition comments, or not concerned with duplicate definitions, you can safely disable this rule.

‎src/rules/no-duplicate-definitions.js‎

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/**
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* @fileoverview Rule to prevent duplicate definitions in Markdown.
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* @author 루밀LuMir(lumirlumir)
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*/
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//-----------------------------------------------------------------------------
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// Type Definitions
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//-----------------------------------------------------------------------------
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/**
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* @typedef {import("../types.ts").MarkdownRuleDefinition<{ RuleOptions: [{ allowDefinitions: string[], allowFootnoteDefinitions: string[]; }]; }>}
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* NoDuplicateDefinitionsRuleDefinition
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*/
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//-----------------------------------------------------------------------------
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// Rule Definition
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//-----------------------------------------------------------------------------
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/** @type {NoDuplicateDefinitionsRuleDefinition} */
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export default {
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meta: {
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type: "problem",
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docs: {
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recommended: true,
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description: "Disallow duplicate definitions",
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url: "https://github.com/eslint/markdown/blob/main/docs/rules/no-duplicate-definitions.md",
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},
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messages: {
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duplicateDefinition: "Unexpected duplicate definition found.",
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duplicateFootnoteDefinition:
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"Unexpected duplicate footnote definition found.",
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},
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schema: [
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{
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type: "object",
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properties: {
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allowDefinitions: {
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type: "array",
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items: {
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type: "string",
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},
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uniqueItems: true,
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},
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allowFootnoteDefinitions: {
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type: "array",
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items: {
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type: "string",
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},
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uniqueItems: true,
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},
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},
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additionalProperties: false,
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},
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],
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defaultOptions: [
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{
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allowDefinitions: ["//"],
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allowFootnoteDefinitions: [],
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},
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],
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},
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create(context) {
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const allowDefinitions = new Set(context.options[0]?.allowDefinitions);
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const allowFootnoteDefinitions = new Set(
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context.options[0]?.allowFootnoteDefinitions,
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);
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const definitions = new Set();
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const footnoteDefinitions = new Set();
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return {
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definition(node) {
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if (allowDefinitions.has(node.identifier)) {
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return;
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}
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if (definitions.has(node.identifier)) {
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context.report({
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node,
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messageId: "duplicateDefinition",
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});
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} else {
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definitions.add(node.identifier);
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}
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},
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footnoteDefinition(node) {
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if (allowFootnoteDefinitions.has(node.identifier)) {
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return;
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}
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if (footnoteDefinitions.has(node.identifier)) {
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context.report({
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node,
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messageId: "duplicateFootnoteDefinition",
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});
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} else {
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footnoteDefinitions.add(node.identifier);
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}
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},
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};
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},
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};

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