fix: use output filename in TypeScript usage imports

packages/quicktype-core/src/language/JavaScript/JavaScriptRenderer.ts

@@ -493,15 +493,27 @@ function r(name${stringAnnotation}) {
 
     protected emitTypes(): void {}
 
-    protected emitUsageImportComment(): void {
-        this.emitLine('//   const Convert = require("./file");');
+    protected usageModuleName(givenOutputFilename: string): string {
+        return givenOutputFilename === "stdout"
+            ? "file"
+            : givenOutputFilename
+                  .replace(/^.*[/\\]/, "")
+                  .replace(/\.[^.]+$/, "");
+    }
+
+    protected emitUsageImportComment(givenOutputFilename: string): void {
+        this.emitLine(
+            '//   const Convert = require("./',
+            this.usageModuleName(givenOutputFilename),
+            '");',
+        );
     }
 
-    protected emitUsageComments(): void {
+    protected emitUsageComments(givenOutputFilename: string): void {
         this.emitMultiline(`// To parse this data:
 //`);
 
-        this.emitUsageImportComment();
+        this.emitUsageImportComment(givenOutputFilename);
         this.emitLine("//");
         this.forEachTopLevel("none", (_t, name) => {
             const camelCaseName = modifySource(camelCase, name);
@@ -537,11 +549,11 @@ function r(name${stringAnnotation}) {
         });
     }
 
-    protected emitSourceStructure(): void {
+    protected emitSourceStructure(givenOutputFilename: string): void {
         if (this.leadingComments !== undefined) {
             this.emitComments(this.leadingComments);
         } else {
-            this.emitUsageComments();
+            this.emitUsageComments(givenOutputFilename);
         }
 
         this.emitTypes();

packages/quicktype-core/src/language/TypeScriptFlow/FlowRenderer.ts

@@ -39,9 +39,9 @@ export class FlowRenderer extends TypeScriptFlowBaseRenderer {
         });
     }
 
-    protected emitSourceStructure(): void {
+    protected emitSourceStructure(givenOutputFilename: string): void {
         this.emitLine("// @flow");
         this.ensureBlankLine();
-        super.emitSourceStructure();
+        super.emitSourceStructure(givenOutputFilename);
     }
 }

packages/quicktype-core/src/language/TypeScriptFlow/TypeScriptFlowBaseRenderer.ts

@@ -191,9 +191,9 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
         );
     }
 
-    protected emitUsageComments(): void {
+    protected emitUsageComments(givenOutputFilename: string): void {
         if (this._tsFlowOptions.justTypes) return;
-        super.emitUsageComments();
+        super.emitUsageComments(givenOutputFilename);
     }
 
     protected deserializerFunctionLine(t: Type, name: Name): Sourcelike {

packages/quicktype-core/src/language/TypeScriptFlow/TypeScriptRenderer.ts

@@ -50,7 +50,7 @@ export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
 
     protected emitModuleExports(): void {}
 
-    protected emitUsageImportComment(): void {
+    protected emitUsageImportComment(givenOutputFilename: string): void {
         const topLevelNames: Sourcelike[] = [];
         this.forEachTopLevel(
             "none",
@@ -62,7 +62,9 @@ export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
         this.emitLine(
             "//   import { Convert",
             topLevelNames,
-            ' } from "./file";',
+            ' } from "./',
+            this.usageModuleName(givenOutputFilename),
+            '";',
         );
     }
 

test/unit/typescript-output-filename.test.ts

@@ -0,0 +1,70 @@
+import { describe, expect, test } from "vitest";
+
+import {
+    InputData,
+    jsonInputForTargetLanguage,
+    quicktype,
+} from "../../packages/quicktype-core/src/index.js";
+
+async function generate(
+    lang: string,
+    outputFilename?: string,
+): Promise<string> {
+    const jsonInput = jsonInputForTargetLanguage(lang);
+    await jsonInput.addSource({
+        name: "ExperimentCounts",
+        samples: ['{"experiments": 3}'],
+    });
+
+    const inputData = new InputData();
+    inputData.addInput(jsonInput);
+    const result = await quicktype({
+        inputData,
+        lang,
+        outputFilename,
+    });
+    return result.lines.join("\n");
+}
+
+describe("output filename in usage comments", () => {
+    test("uses output filename in TypeScript usage imports", async () => {
+        const output = await generate(
+            "typescript",
+            "src/cli/ExperimentCounts.ts",
+        );
+
+        expect(output).toContain(
+            '//   import { Convert, ExperimentCounts } from "./ExperimentCounts";',
+        );
+        expect(output).not.toContain('from "./file"');
+    });
+
+    test("uses output filename in JavaScript usage require", async () => {
+        const output = await generate(
+            "javascript",
+            "src/cli/ExperimentCounts.js",
+        );
+
+        expect(output).toContain(
+            '//   const Convert = require("./ExperimentCounts");',
+        );
+        expect(output).not.toContain('require("./file")');
+    });
+
+    test("uses output filename in Flow usage require", async () => {
+        const output = await generate("flow", "ExperimentCounts.js");
+
+        expect(output).toContain(
+            '//   const Convert = require("./ExperimentCounts");',
+        );
+        expect(output).not.toContain('require("./file")');
+    });
+
+    test('falls back to "file" when writing to stdout', async () => {
+        const tsOutput = await generate("typescript");
+        expect(tsOutput).toContain(' } from "./file";');
+
+        const jsOutput = await generate("javascript");
+        expect(jsOutput).toContain('//   const Convert = require("./file");');
+    });
+});