fix(41244): ignore synthesized imports (microsoft#41267)

Author: a-tarasyuk

src/services/utilities.ts

@@ -1827,7 +1827,9 @@ namespace ts {
             return preferences.quotePreference === "single" ? QuotePreference.Single : QuotePreference.Double;
         }
         else {
-            const firstModuleSpecifier = sourceFile.imports && find(sourceFile.imports, isStringLiteral);
+            // ignore synthetic import added when importHelpers: true
+            const firstModuleSpecifier = sourceFile.imports &&
+                find(sourceFile.imports, n => isStringLiteral(n) && !nodeIsSynthesized(n.parent)) as StringLiteral;
             return firstModuleSpecifier ? quotePreferenceFromString(firstModuleSpecifier, sourceFile) : QuotePreference.Double;
         }
     }

tests/cases/fourslash/importFixes_quotePreferenceDouble_importHelpers.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts'/>
+
+// @importHelpers: true
+// @filename: /a.ts
+////export default () => {};
+
+// @filename: /b.ts
+////export default () => {};
+
+// @filename: /test.ts
+////import a from "./a";
+////[|b|];
+
+goTo.file("/test.ts");
+verify.importFixAtPosition([`import b from "./b";
+b`]);

tests/cases/fourslash/importFixes_quotePreferenceSingle_importHelpers.ts

@@ -0,0 +1,16 @@
+/// <reference path='fourslash.ts'/>
+
+// @importHelpers: true
+// @filename: /a.ts
+////export default () => {};
+
+// @filename: /b.ts
+////export default () => {};
+
+// @filename: /test.ts
+////import a from './a';
+////[|b|];
+
+goTo.file("/test.ts");
+verify.importFixAtPosition([`import b from './b';
+b`]);