fix(ng-update): do not always use double quotes for generated imports (#16131)

Currently when someone uses single quote import declarations in
their project and the `ng update` migration for Material runs, the
Material imports are rewritten into multiple imports referring to
individual secondary entry-points, but the actual existing quote
style is ignored. This means that the linter can sometimes complain
after the migration has been performed.

Ideally we'd run the tslint fix task after the migration ran in order to
fix all lint rule failures which are specific to the given project, but this
is not a best-practice yet and we need to decide on the CLI-side whether
the CLI should automatically run the fixers after generator/migration
schematics ran. See: angular/angular-cli#14532

Unfortunately we can't do the same thing for the whitespace within
the `NamedImports` declaration because the whitespace for object
literal expressions is hard-coded. See:

https://github.com/microsoft/TypeScript/blob/6a559e37ee0d660fcc94f086a34370e79e94b17a/src/compiler/emitter.ts#L3796-L3797
(`emitObjectLiteralExpression` does not allow configuring the format flags)

Fixes #14532

Author: devversion

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);