Add JSDoc eslint rule

See the next commit for a more fleshed-out description.

.eslintrc.json

@@ -87,6 +87,7 @@
         "local/simple-indent": "error",
         "local/debug-assert": "error",
         "local/no-keywords": "error",
+        "local/jsdoc-format": "error",
 
         // eslint-plugin-import
         "import/no-extraneous-dependencies": ["error", { "optionalDependencies": false }],

scripts/eslint/rules/jsdoc-format.cjs

@@ -0,0 +1,110 @@
+const { TSESTree } = require("@typescript-eslint/utils");
+const { createRule } = require("./utils.cjs");
+
+module.exports = createRule({
+    name: "jsdoc-format",
+    meta: {
+        docs: {
+            description: ``,
+            recommended: "error",
+        },
+        messages: {
+            internalCommentInNonJSDocError: `@internal should not appear in non-JSDoc comment for declaration.`,
+            internalCommentNotLastError: `@internal should only appear in final JSDoc comment for declaration.`,
+            multipleJSDocError: `Declaration has multiple JSDoc comments.`,
+            internalCommentOnParameterProperty: `@internal cannot appear on a JSDoc comment; use a declared property and an assignment in the constructor instead.`,
+        },
+        schema: [],
+        type: "problem",
+    },
+    defaultOptions: [],
+
+    create(context) {
+        const sourceCode = context.getSourceCode();
+        const atInternal = "@internal";
+        const jsdocStart = "/**";
+
+        /** @type {(c: TSESTree.Comment, indexInComment: number) => TSESTree.SourceLocation} */
+        const getAtInternalLoc = (c, indexInComment) => {
+            const line = c.loc.start.line;
+            return {
+                start: {
+                    line,
+                    column: c.loc.start.column + indexInComment,
+                },
+                end: {
+                    line,
+                    column: c.loc.start.column + indexInComment + atInternal.length,
+                },
+            };
+        };
+
+        /** @type {(c: TSESTree.Comment) => TSESTree.SourceLocation} */
+        const getJSDocStartLoc = (c) => {
+            return {
+                start: c.loc.start,
+                end: {
+                    line: c.loc.start.line,
+                    column: c.loc.start.column + jsdocStart.length,
+                },
+            };
+        };
+
+        /** @type {(node: TSESTree.Node) => void} */
+        const checkJSDocFormat = (node) => {
+            const blockComments = sourceCode.getCommentsBefore(node).filter(c => c.type === "Block");
+            if (blockComments.length === 0) {
+                return;
+            }
+
+            const last = blockComments.length - 1;
+            let seenJSDoc = false;
+            for (let i = 0; i < blockComments.length; i++) {
+                const c = blockComments[i];
+                const rawComment = sourceCode.getText(c);
+
+                const isJSDoc = rawComment.startsWith(jsdocStart);
+                if (isJSDoc && seenJSDoc) {
+                    context.report({ messageId: "multipleJSDocError", node: c, loc: getJSDocStartLoc(c) });
+                }
+                seenJSDoc = seenJSDoc || isJSDoc;
+
+                const indexInComment = rawComment.indexOf(atInternal);
+                if (indexInComment === -1) {
+                    continue;
+                }
+
+                if (!isJSDoc) {
+                    context.report({ messageId: "internalCommentInNonJSDocError", node: c, loc: getAtInternalLoc(c, indexInComment) });
+                }
+                else if (i !== last) {
+                    context.report({ messageId: "internalCommentNotLastError", node: c, loc: getAtInternalLoc(c, indexInComment) });
+                }
+                else if (node.type === "TSParameterProperty") {
+                    context.report({ messageId: "internalCommentOnParameterProperty", node: c, loc: getAtInternalLoc(c, indexInComment) });
+                }
+            }
+        };
+
+        return {
+            ClassDeclaration: checkJSDocFormat,
+            FunctionDeclaration: checkJSDocFormat,
+            TSEnumDeclaration: checkJSDocFormat,
+            TSModuleDeclaration: checkJSDocFormat,
+            VariableDeclaration: checkJSDocFormat,
+            TSInterfaceDeclaration: checkJSDocFormat,
+            TSTypeAliasDeclaration: checkJSDocFormat,
+            TSCallSignatureDeclaration: checkJSDocFormat,
+            ExportAllDeclaration: checkJSDocFormat,
+            ExportNamedDeclaration: checkJSDocFormat,
+            TSImportEqualsDeclaration: checkJSDocFormat,
+            TSNamespaceExportDeclaration: checkJSDocFormat,
+            TSConstructSignatureDeclaration: checkJSDocFormat,
+            ExportDefaultDeclaration: checkJSDocFormat,
+            TSPropertySignature: checkJSDocFormat,
+            TSIndexSignature: checkJSDocFormat,
+            TSMethodSignature: checkJSDocFormat,
+            TSParameterProperty: checkJSDocFormat,
+        };
+    },
+});