fix(42019): Quick info on implementation is missing JSDoc tags from interface declaration

src/compiler/utilities.ts

@@ -2992,7 +2992,7 @@ namespace ts {
     }
 
     export function getEffectiveImplementsTypeNodes(node: ClassLikeDeclaration): undefined | readonly ExpressionWithTypeArguments[]{
-        if(isInJSFile(node)) {
+        if (isInJSFile(node)) {
             return getJSDocImplementsTags(node).map(n => n.class);
         }
         else {

src/services/services.ts

@@ -550,9 +550,8 @@ namespace ts {
 
         getJsDocTags(): JSDocTagInfo[] {
             if (this.jsDocTags === undefined) {
-                this.jsDocTags = this.declaration ? JsDoc.getJsDocTagsFromDeclarations([this.declaration]) : [];
+                this.jsDocTags = this.declaration ? getJsDocTags([this.declaration], this.checker) : [];
             }
-
             return this.jsDocTags;
         }
     }
@@ -566,34 +565,37 @@ namespace ts {
         return getJSDocTags(node).some(tag => tag.tagName.text === "inheritDoc");
     }
 
+    function getJsDocTags(declarations: Declaration[], checker: TypeChecker): JSDocTagInfo[] {
+        let tags = JsDoc.getJsDocTagsFromDeclarations(declarations);
+        if (tags.length === 0 || declarations.some(hasJSDocInheritDocTag)) {
+            forEachUnique(declarations, declaration => {
+                const inheritedTags = findBaseOfDeclaration(checker, declaration, symbol => symbol.getJsDocTags());
+                if (inheritedTags) {
+                    tags = [...inheritedTags, ...tags];
+                }
+            });
+        }
+        return tags;
+    }
+
     function getDocumentationComment(declarations: readonly Declaration[] | undefined, checker: TypeChecker | undefined): SymbolDisplayPart[] {
         if (!declarations) return emptyArray;
 
         let doc = JsDoc.getJsDocCommentsFromDeclarations(declarations);
-        if (doc.length === 0 || declarations.some(hasJSDocInheritDocTag)) {
+        if (checker && (doc.length === 0 || declarations.some(hasJSDocInheritDocTag))) {
             forEachUnique(declarations, declaration => {
-                const inheritedDocs = findInheritedJSDocComments(declaration, declaration.symbol.name, checker!); // TODO: GH#18217
+                const inheritedDocs = findBaseOfDeclaration(checker, declaration, symbol => symbol.getDocumentationComment(checker));
                 // TODO: GH#16312 Return a ReadonlyArray, avoid copying inheritedDocs
                 if (inheritedDocs) doc = doc.length === 0 ? inheritedDocs.slice() : inheritedDocs.concat(lineBreakPart(), doc);
             });
         }
         return doc;
     }
 
-    /**
-     * Attempts to find JSDoc comments for possibly-inherited properties.  Checks superclasses then traverses
-     * implemented interfaces until a symbol is found with the same name and with documentation.
-     * @param declaration The possibly-inherited declaration to find comments for.
-     * @param propertyName The name of the possibly-inherited property.
-     * @param typeChecker A TypeChecker, used to find inherited properties.
-     * @returns A filled array of documentation comments if any were found, otherwise an empty array.
-     */
-    function findInheritedJSDocComments(declaration: Declaration, propertyName: string, typeChecker: TypeChecker): readonly SymbolDisplayPart[] | undefined {
+    function findBaseOfDeclaration<T>(checker: TypeChecker, declaration: Declaration, cb: (symbol: Symbol) => T[]): T[] | undefined {
         return firstDefined(declaration.parent ? getAllSuperTypeNodes(declaration.parent) : emptyArray, superTypeNode => {
-            const superType = typeChecker.getTypeAtLocation(superTypeNode);
-            const baseProperty = superType && typeChecker.getPropertyOfType(superType, propertyName);
-            const inheritedDocs = baseProperty && baseProperty.getDocumentationComment(typeChecker);
-            return inheritedDocs && inheritedDocs.length ? inheritedDocs : undefined;
+            const symbol = checker.getPropertyOfType(checker.getTypeAtLocation(superTypeNode), declaration.symbol.name);
+            return symbol ? cb(symbol) : undefined;
         });
     }
 

tests/baselines/reference/quickInfoJsDocTags1.baseline

@@ -0,0 +1,110 @@
+[
+  {
+    "marker": {
+      "fileName": "/tests/cases/fourslash/quickInfoJsDocTags1.ts",
+      "position": 298
+    },
+    "quickInfo": {
+      "kind": "function",
+      "kindModifiers": "",
+      "textSpan": {
+        "start": 298,
+        "length": 3
+      },
+      "displayParts": [
+        {
+          "text": "function",
+          "kind": "keyword"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "foo",
+          "kind": "functionName"
+        },
+        {
+          "text": "(",
+          "kind": "punctuation"
+        },
+        {
+          "text": "x",
+          "kind": "parameterName"
+        },
+        {
+          "text": ":",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "any",
+          "kind": "keyword"
+        },
+        {
+          "text": ")",
+          "kind": "punctuation"
+        },
+        {
+          "text": ":",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "void",
+          "kind": "keyword"
+        }
+      ],
+      "documentation": [
+        {
+          "text": "Doc",
+          "kind": "text"
+        }
+      ],
+      "tags": [
+        {
+          "name": "author",
+          "text": "Me <[email protected]>"
+        },
+        {
+          "name": "augments",
+          "text": "C<T> Augments it"
+        },
+        {
+          "name": "template",
+          "text": "T A template"
+        },
+        {
+          "name": "type",
+          "text": "{number | string} A type"
+        },
+        {
+          "name": "typedef",
+          "text": "NumOrStr"
+        },
+        {
+          "name": "property",
+          "text": "{number} x The prop"
+        },
+        {
+          "name": "param",
+          "text": "x The param"
+        },
+        {
+          "name": "returns",
+          "text": "The result"
+        },
+        {
+          "name": "see",
+          "text": "x (the parameter)"
+        }
+      ]
+    }
+  }
+]

tests/baselines/reference/quickInfoJsDocTags3.baseline

@@ -0,0 +1,94 @@
+[
+  {
+    "marker": {
+      "fileName": "/tests/cases/fourslash/quickInfoJsDocTags3.ts",
+      "position": 290
+    },
+    "quickInfo": {
+      "kind": "method",
+      "kindModifiers": "",
+      "textSpan": {
+        "start": 290,
+        "length": 6
+      },
+      "displayParts": [
+        {
+          "text": "(",
+          "kind": "punctuation"
+        },
+        {
+          "text": "method",
+          "kind": "text"
+        },
+        {
+          "text": ")",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "Bar",
+          "kind": "className"
+        },
+        {
+          "text": ".",
+          "kind": "punctuation"
+        },
+        {
+          "text": "method",
+          "kind": "methodName"
+        },
+        {
+          "text": "(",
+          "kind": "punctuation"
+        },
+        {
+          "text": ")",
+          "kind": "punctuation"
+        },
+        {
+          "text": ":",
+          "kind": "punctuation"
+        },
+        {
+          "text": " ",
+          "kind": "space"
+        },
+        {
+          "text": "void",
+          "kind": "keyword"
+        }
+      ],
+      "documentation": [
+        {
+          "text": "comment",
+          "kind": "text"
+        }
+      ],
+      "tags": [
+        {
+          "name": "author",
+          "text": "Me <[email protected]>"
+        },
+        {
+          "name": "see",
+          "text": "x (the parameter)"
+        },
+        {
+          "name": "param",
+          "text": "x - x comment"
+        },
+        {
+          "name": "param",
+          "text": "y - y comment"
+        },
+        {
+          "name": "throws",
+          "text": "{Error} comment"
+        }
+      ]
+    }
+  }
+]