fix(51072): ts.preProcessFile finds import in template string after conditional expression with template strings (#51082)

Author: a-tarasyuk

src/services/preProcess.ts

@@ -347,8 +347,8 @@ namespace ts {
 
                 if (scanner.getToken() === SyntaxKind.TemplateHead) {
                     const stack = [scanner.getToken()];
-                    let token = scanner.scan();
                     loop: while (length(stack)) {
+                        const token = scanner.scan();
                         switch (token) {
                             case SyntaxKind.EndOfFileToken:
                                 break loop;
@@ -376,7 +376,6 @@ namespace ts {
                                 }
                                 break;
                         }
-                        token = scanner.scan();
                     }
                     nextToken();
                 }

src/testRunner/unittests/services/preProcessFile.ts

@@ -205,6 +205,22 @@ describe("unittests:: services:: PreProcessFile:", () => {
             /* eslint-enable no-template-curly-in-string */
         });
 
+        it("Ignores imports in template strings", () => {
+            /* eslint-disable no-template-curly-in-string */
+            test("a ? `&${a}` : `#${b}`;\n\n `import(\"${moduleSpecifier}\").${id}`;",
+            /*readImportFile*/ true,
+            /*detectJavaScriptImports*/ true,
+            {
+                referencedFiles: [],
+                typeReferenceDirectives: [],
+                libReferenceDirectives: [],
+                importedFiles: [],
+                ambientExternalModules: undefined,
+                isLibFile: false
+            });
+            /* eslint-enable no-template-curly-in-string */
+        });
+
         it("Correctly returns imports after a template expression", () => {
             /* eslint-disable no-template-curly-in-string */
             test("`${foo}`; import \"./foo\";",