fix(ng-update): do not always use double quotes for generated imports

src/material/schematics/ng-update/test-cases/misc/material-imports_expected_output.ts

@@ -1,18 +1,18 @@
-import { c as c2 } from "@angular/material/c";
-import { a } from "@angular/material/a";
-import { b } from "@angular/material/b";
-import { c } from "@angular/material/c";
-import { a as a2 } from "@angular/material/a";
+import { c as c2 } from '@angular/material/c';
+import { a } from '@angular/material/a';
+import { b } from '@angular/material/b';
+import { c } from '@angular/material/c';
+import { a as a2 } from '@angular/material/a';
 
 // unsorted
-import { a } from "@angular/material/a";
-import { b } from "@angular/material/b";
-import { c } from "@angular/material/c";
+import { a } from '@angular/material/a';
+import { b } from '@angular/material/b';
+import { c } from '@angular/material/c';
 
-import { /* comment */ a as a3 } from "@angular/material/a";
+import { /* comment */ a as a3 } from '@angular/material/a';
 
 // primary entry-point export
-import { VERSION } from "@angular/material/core";
+import { VERSION } from '@angular/material/core';
 
 // type import
 import { SomeInterface } from "@angular/material/types";

src/material/schematics/ng-update/test-cases/misc/material-imports_input.ts

@@ -11,4 +11,4 @@ import {/* comment */ a as a3} from '@angular/material';
 import {VERSION} from '@angular/material';
 
 // type import
-import {SomeInterface} from '@angular/material';
+import {SomeInterface} from "@angular/material";

src/material/schematics/ng-update/upgrade-rules/package-imports-v8/updateAngularMaterialImportsRule.ts

@@ -88,6 +88,9 @@ function walk(ctx: Lint.WalkContext<boolean>, checker: ts.TypeChecker): void {
       return ctx.addFailureAtNode(declaration, Rule.NO_IMPORT_NAMED_SYMBOLS_FAILURE_STR);
     }
 
+    // Whether the existing import declaration is using a single quote module specifier.
+    const singleQuoteImport = declaration.moduleSpecifier.getText()[0] === `'`;
+
     // Map which consists of secondary entry-points and import specifiers which are used
     // within the current import declaration.
     const importMap = new Map<string, ts.ImportSpecifier[]>();
@@ -144,7 +147,7 @@ function walk(ctx: Lint.WalkContext<boolean>, checker: ts.TypeChecker): void {
               const newImport = ts.createImportDeclaration(
                   undefined, undefined,
                   ts.createImportClause(undefined, ts.createNamedImports(elements)),
-                  ts.createStringLiteral(`${materialModuleSpecifier}/${name}`));
+                  createStringLiteral(`${materialModuleSpecifier}/${name}`, singleQuoteImport));
               return printer.printNode(ts.EmitHint.Unspecified, newImport, sf);
             })
             .join('\n');
@@ -166,6 +169,18 @@ function walk(ctx: Lint.WalkContext<boolean>, checker: ts.TypeChecker): void {
   sf.statements.forEach(cb);
 }
 
+/**
+ * Creates a string literal from the specified text.
+ * @param text Text of the string literal.
+ * @param singleQuotes Whether single quotes should be used when printing the literal node.
+ */
+function createStringLiteral(text: string, singleQuotes: boolean): ts.StringLiteral {
+  const literal = ts.createStringLiteral(text);
+  // See: https://github.com/microsoft/TypeScript/blob/master/src/compiler/utilities.ts#L584-L590
+  literal['singleQuote'] = singleQuotes;
+  return literal;
+}
+
 /** Gets the symbol that contains the value declaration of the given node. */
 function getDeclarationSymbolOfNode(node: ts.Node, checker: ts.TypeChecker): ts.Symbol|undefined {
   const symbol = checker.getSymbolAtLocation(node);