feat: Ability to set a IndexSignatureDeclaration's return type using …

…a writer function.

src/compiler/interface/IndexSignatureDeclaration.ts

@@ -1,5 +1,7 @@
 import { ts } from "../../typescript";
 import { IndexSignatureDeclarationStructure } from "../../structures";
+import { CodeBlockWriter } from "../../codeBlockWriter";
+import { getTextFromStringOrWriter } from "../../utils";
 import { removeInterfaceMember } from "../../manipulation";
 import { callBaseFill } from "../callBaseFill";
 import { Node, Identifier } from "../common";
@@ -93,10 +95,19 @@ export class IndexSignatureDeclaration extends IndexSignatureDeclarationBase<ts.
 
     /**
      * Sets the return type.
-     * @param text
+     * @param text - Text of the return type.
      */
-    setReturnType(text: string) {
+    setReturnType(text: string): this;
+    /**
+     * Sets the return type.
+     * @param writerFunction - Writer function to write the return type with.
+     */
+    setReturnType(writerFunction: (writer: CodeBlockWriter) => void): this;
+    /** @internal */
+    setReturnType(textOrWriterFunction: string | ((writer: CodeBlockWriter) => void)): this;
+    setReturnType(textOrWriterFunction: string | ((writer: CodeBlockWriter) => void)) {
         const returnTypeNode = this.getReturnTypeNode();
+        const text = getTextFromStringOrWriter(this.getWriterWithQueuedChildIndentation(), textOrWriterFunction);
         if (returnTypeNode.getText() === text)
             return this;
 

src/structurePrinters/interface/IndexSignatureDeclarationStructurePrinter.ts

@@ -1,4 +1,5 @@
 import { CodeBlockWriter } from "../../codeBlockWriter";
+import { printTextFromStringOrWriter } from "../../utils";
 import { IndexSignatureDeclarationStructure } from "../../structures";
 import { FactoryStructurePrinter } from "../FactoryStructurePrinter";
 import { NewLineFormattingStructuresPrinter } from "../formatting";
@@ -13,6 +14,8 @@ export class IndexSignatureDeclarationStructurePrinter extends FactoryStructureP
     printText(writer: CodeBlockWriter, structure: IndexSignatureDeclarationStructure) {
         this.factory.forJSDoc().printDocs(writer, structure.docs);
         this.factory.forModifierableNode().printText(writer, structure);
-        writer.write(`[${structure.keyName || "key"}: ${structure.keyType || "string"}]: ${structure.returnType};`);
+        writer.write(`[${structure.keyName || "key"}: ${structure.keyType || "string"}]: `);
+        printTextFromStringOrWriter(writer, structure.returnType);
+        writer.write(";");
     }
 }

src/structures/interface/IndexSignatureDeclarationStructure.ts

@@ -1,7 +1,8 @@
-import { JSDocableNodeStructure, ReadonlyableNodeStructure } from "../base";
+import { CodeBlockWriter } from "../../codeBlockWriter";
+import { JSDocableNodeStructure, ReadonlyableNodeStructure } from "../base";
 
 export interface IndexSignatureDeclarationStructure extends JSDocableNodeStructure, ReadonlyableNodeStructure {
     keyName?: string;
     keyType?: string;
-    returnType: string;
+    returnType: string | ((writer: CodeBlockWriter) => void);
 }

src/tests/compiler/base/typeElementMemberedNodeTests.ts

@@ -132,7 +132,7 @@ describe(nameof(TypeElementMemberedNode), () => {
 
         it("should insert multiple into other", () => {
             doTest("interface i {\n    method1();\n    method2();\n}", 1,
-                [{ returnType: "number" }, { keyName: "key2", keyType: "number", returnType: "Date" }],
+                [{ returnType: "number" }, { keyName: "key2", keyType: "number", returnType: writer => writer.write("Date") }],
                 "interface i {\n    method1();\n    [key: string]: number;\n    [key2: number]: Date;\n    method2();\n}");
         });
 

src/tests/compiler/interface/indexSignatureDeclarationTests.ts

@@ -1,4 +1,5 @@
 import { expect } from "chai";
+import { CodeBlockWriter } from "../../../codeBlockWriter";
 import { IndexSignatureDeclaration, InterfaceDeclaration } from "../../../compiler";
 import { IndexSignatureDeclarationStructure } from "../../../structures";
 import { getInfoFromText } from "../testHelpers";
@@ -31,6 +32,11 @@ describe(nameof(IndexSignatureDeclaration), () => {
             doTest("interface Identifier {\n    [key: string]: SomeReference;\n}", allProps,
                 "interface Identifier {\n    /**\n     * Desc\n     */\n    readonly [newKeyName: number]: Date;\n}");
         });
+
+        it("should change the return type when using a writer", () => {
+            doTest("interface Identifier { [key: string]: number; }", { returnType: writer => writer.write("string") },
+                "interface Identifier { [key: string]: string; }");
+        });
     });
 
     describe(nameof<IndexSignatureDeclaration>(n => n.getKeyName), () => {
@@ -124,15 +130,19 @@ describe(nameof(IndexSignatureDeclaration), () => {
     });
 
     describe(nameof<IndexSignatureDeclaration>(n => n.setReturnType), () => {
-        function doTest(code: string, name: string, expectedCode: string) {
+        function doTest(code: string, textOrWriterFunction: string | ((writer: CodeBlockWriter) => void), expectedCode: string) {
             const {firstIndexSignature, sourceFile} = getFirstIndexSignatureWithInfo(code);
-            firstIndexSignature.setReturnType(name);
+            firstIndexSignature.setReturnType(textOrWriterFunction);
             expect(sourceFile.getFullText()).to.equal(expectedCode);
         }
 
         it("should set the return type", () => {
             doTest("interface Identifier { [keyName: string]: number; }", "Date", "interface Identifier { [keyName: string]: Date; }");
         });
+
+        it("should set the return type with a writer function", () => {
+            doTest("interface Identifier { [keyName: string]: number; }", writer => writer.write("Date"), "interface Identifier { [keyName: string]: Date; }");
+        });
     });
 
     describe(nameof<IndexSignatureDeclaration>(n => n.setIsReadonly), () => {