Support semantic highlights for JS files (#43992)

* Switches from never allowing semantic highlight on JS to only doing it if we have a valid source file

* Adds a way to test and validate that an arbitrary JS file gets semantic classification results

* Revert to just dropping the if statement

src/harness/client.ts

@@ -772,8 +772,10 @@ namespace ts.server {
             return notImplemented();
         }
 
-        getEncodedSemanticClassifications(_fileName: string, _span: TextSpan, _format?: SemanticClassificationFormat): Classifications {
-            return notImplemented();
+        getEncodedSemanticClassifications(file: string, span: TextSpan, format?: SemanticClassificationFormat): Classifications {
+            const request = this.processRequest<protocol.EncodedSemanticClassificationsRequest>(protocol.CommandTypes.EncodedSemanticClassificationsFull, { file, start: span.start, length: span.length, format });
+            const r = this.processResponse<protocol.EncodedSemanticClassificationsResponse>(request);
+            return r.body!;
         }
 
         private convertCallHierarchyItem(item: protocol.CallHierarchyItem): CallHierarchyItem {

src/harness/fourslashImpl.ts

@@ -2746,6 +2746,12 @@ namespace FourSlash {
             // fs.writeFileSync(testfilePath, newfile);
         }
 
+        public verifyEncodedSemanticClassificationsLength(format: ts.SemanticClassificationFormat, expected: number) {
+            const actual = this.languageService.getEncodedSemanticClassifications(this.activeFile.fileName, ts.createTextSpan(0, this.activeFile.content.length), format);
+            if (actual.spans.length !== expected) {
+                this.raiseError(`encodedSemanticClassificationsLength failed - expected total spans to be ${expected} got ${actual.spans.length}`);
+            }
+        }
 
         public verifySemanticClassifications(format: ts.SemanticClassificationFormat, expected: { classificationType: string | number; text?: string }[]) {
             const actual = this.languageService.getSemanticClassifications(this.activeFile.fileName,

src/harness/fourslashInterfaceImpl.ts

@@ -537,6 +537,10 @@ namespace FourSlashInterface {
             this.state.verifySyntacticClassifications(classifications);
         }
 
+        public encodedSemanticClassificationsLength(format: ts.SemanticClassificationFormat, length: number) {
+            this.state.verifyEncodedSemanticClassificationsLength(format, length);
+        }
+
         /**
          * This method *requires* an ordered stream of classifications for a file, and spans are highly recommended.
          */

src/services/services.ts

@@ -1882,17 +1882,8 @@ namespace ts {
             return NavigationBar.getNavigationTree(syntaxTreeCache.getCurrentSourceFile(fileName), cancellationToken);
         }
 
-        function isTsOrTsxFile(fileName: string): boolean {
-            const kind = getScriptKind(fileName, host);
-            return kind === ScriptKind.TS || kind === ScriptKind.TSX;
-        }
-
         function getSemanticClassifications(fileName: string, span: TextSpan): ClassifiedSpan[];
         function getSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): ClassifiedSpan[] | ClassifiedSpan2020[] {
-            if (!isTsOrTsxFile(fileName)) {
-                // do not run semantic classification on non-ts-or-tsx files
-                return [];
-            }
             synchronizeHostData();
 
             const responseFormat = format || SemanticClassificationFormat.Original;
@@ -1905,10 +1896,6 @@ namespace ts {
         }
 
         function getEncodedSemanticClassifications(fileName: string, span: TextSpan, format?: SemanticClassificationFormat): Classifications {
-            if (!isTsOrTsxFile(fileName)) {
-                // do not run semantic classification on non-ts-or-tsx files
-                return { spans: [], endOfLineState: EndOfLineState.None };
-            }
             synchronizeHostData();
 
             const responseFormat = format || SemanticClassificationFormat.Original;

tests/cases/fourslash/fourslash.ts

@@ -358,6 +358,8 @@ declare namespace FourSlashInterface {
         rangesAreDocumentHighlights(ranges?: Range[], options?: VerifyDocumentHighlightsOptions): void;
         rangesWithSameTextAreDocumentHighlights(): void;
         documentHighlightsOf(startRange: Range, ranges: Range[], options?: VerifyDocumentHighlightsOptions): void;
+        /** Prefer semanticClassificationsAre for more descriptive tests */
+        encodedSemanticClassificationsLength(format: "original" | "2020", length: number)
         /**
          * This method *requires* a contiguous, complete, and ordered stream of classifications for a file.
          */

tests/cases/fourslash/semanticClassificationJs.ts

@@ -1,11 +0,0 @@
-/// <reference path="fourslash.ts"/>
-
-// @Filename: app.js
-//// function foo() {
-//// }
-//// let x = 1;
-
-// no semantic classification in js file
-verify.semanticClassificationsAre("original", );
-
-

tests/cases/fourslash/server/semanticClassificationJs1.ts

@@ -0,0 +1,10 @@
+/// <reference path="../fourslash.ts"/>
+
+//// @Filename: index.js
+//// 
+//// var Thing = 0;
+//// Thing.toExponential();
+
+// This test validates that an arbitrary JS file gets 
+// encoded semantic classifications when requested
+verify.encodedSemanticClassificationsLength("2020", 9)