Add fourslash function for validating syntactic classification (microsoft#50362)

Author: DanielRosenwasser

src/harness/fourslashImpl.ts

@@ -2749,6 +2749,13 @@ namespace FourSlash {
             // fs.writeFileSync(testfilePath, newfile);
         }
 
+        public verifyEncodedSyntacticClassificationsLength(expected: number) {
+            const actual = this.languageService.getEncodedSyntacticClassifications(this.activeFile.fileName, ts.createTextSpan(0, this.activeFile.content.length));
+            if (actual.spans.length !== expected) {
+                this.raiseError(`encodedSyntacticClassificationsLength failed - expected total spans to be ${expected} got ${actual.spans.length}`);
+            }
+        }
+
         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) {

src/harness/fourslashInterfaceImpl.ts

@@ -541,6 +541,10 @@ namespace FourSlashInterface {
             this.state.verifySyntacticClassifications(classifications);
         }
 
+        public encodedSyntacticClassificationsLength(length: number) {
+            this.state.verifyEncodedSyntacticClassificationsLength(length);
+        }
+
         public encodedSemanticClassificationsLength(format: ts.SemanticClassificationFormat, length: number) {
             this.state.verifyEncodedSemanticClassificationsLength(format, length);
         }

tests/cases/fourslash/fourslash.ts

@@ -378,8 +378,10 @@ 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)
+        /** Prefer {@link syntacticClassificationsAre} for more descriptive tests */
+        encodedSyntacticClassificationsLength(expected: number): void;
+        /** Prefer {@link semanticClassificationsAre} for more descriptive tests */
+        encodedSemanticClassificationsLength(format: "original" | "2020", length: number): void;
         /**
          * This method *requires* a contiguous, complete, and ordered stream of classifications for a file.
          */