feat: add --prefer-unknown option for TypeScript and Flow

Add a `--prefer-unknown` CLI flag that emits `unknown` instead of `any`
in TypeScript output, and `mixed` instead of `any` in Flow output.

This is a fresh implementation of the feature proposed in PR #2194 by
@RichiCoder1, adapted to the current codebase structure where
TypeScriptFlow was split into multiple files.

Closes #1619

Author: k-vasily

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

@@ -5,15 +5,26 @@ import type { ClassType, EnumType } from "../../Type";
 import type { JavaScriptTypeAnnotations } from "../JavaScript";
 
 import { TypeScriptFlowBaseRenderer } from "./TypeScriptFlowBaseRenderer";
-import { tsFlowTypeAnnotations } from "./utils";
 
 export class FlowRenderer extends TypeScriptFlowBaseRenderer {
+    protected anyType(): string {
+        return this._tsFlowOptions.preferUnknown ? "mixed" : "any";
+    }
+
     protected forbiddenNamesForGlobalNamespace(): string[] {
         return ["Class", "Date", "Object", "String", "Array", "JSON", "Error"];
     }
 
     protected get typeAnnotations(): JavaScriptTypeAnnotations {
-        return Object.assign({ never: "" }, tsFlowTypeAnnotations);
+        const a = this.anyType();
+        return Object.assign({ never: "" }, {
+            any: `: ${a}`,
+            anyArray: `: ${a}[]`,
+            anyMap: `: { [k: string]: ${a} }`,
+            string: ": string",
+            stringArray: ": string[]",
+            boolean: ": boolean",
+        });
     }
 
     protected emitEnum(e: EnumType, enumName: Name): void {

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

@@ -64,7 +64,7 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
 
         return matchType<MultiWord>(
             t,
-            (_anyType) => singleWord("any"),
+            (_anyType) => singleWord(this.anyType()),
             (_nullType) => singleWord("null"),
             (_boolType) => singleWord("boolean"),
             (_integerType) => singleWord("number"),
@@ -113,6 +113,8 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
         );
     }
 
+    protected abstract anyType(): string;
+
     protected abstract emitEnum(e: EnumType, enumName: Name): void;
 
     protected abstract emitClassBlock(c: ClassType, className: Name): void;
@@ -198,7 +200,7 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
 
     protected deserializerFunctionLine(t: Type, name: Name): Sourcelike {
         const jsonType =
-            this._tsFlowOptions.rawType === "json" ? "string" : "any";
+            this._tsFlowOptions.rawType === "json" ? "string" : this.anyType();
         return [
             "function to",
             name,
@@ -212,7 +214,7 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
     protected serializerFunctionLine(t: Type, name: Name): Sourcelike {
         const camelCaseName = modifySource(camelCase, name);
         const returnType =
-            this._tsFlowOptions.rawType === "json" ? "string" : "any";
+            this._tsFlowOptions.rawType === "json" ? "string" : this.anyType();
         return [
             "function ",
             camelCaseName,
@@ -228,9 +230,10 @@ export abstract class TypeScriptFlowBaseRenderer extends JavaScriptRenderer {
     }
 
     protected get castFunctionLines(): [string, string] {
+        const a = this.anyType();
         return [
-            "function cast<T>(val: any, typ: any): T",
-            "function uncast<T>(val: T, typ: any): any",
+            `function cast<T>(val: ${a}, typ: ${a}): T`,
+            `function uncast<T>(val: T, typ: ${a}): ${a}`,
         ];
     }
 

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

@@ -6,16 +6,19 @@ import { isNamedType } from "../../Type/TypeUtils";
 import type { JavaScriptTypeAnnotations } from "../JavaScript";
 
 import { TypeScriptFlowBaseRenderer } from "./TypeScriptFlowBaseRenderer";
-import { tsFlowTypeAnnotations } from "./utils";
 
 export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
+    protected anyType(): string {
+        return this._tsFlowOptions.preferUnknown ? "unknown" : "any";
+    }
+
     protected forbiddenNamesForGlobalNamespace(): string[] {
         return ["Array", "Date"];
     }
 
     protected deserializerFunctionLine(t: Type, name: Name): Sourcelike {
         const jsonType =
-            this._tsFlowOptions.rawType === "json" ? "string" : "any";
+            this._tsFlowOptions.rawType === "json" ? "string" : this.anyType();
         return [
             "public static to",
             name,
@@ -29,7 +32,7 @@ export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
     protected serializerFunctionLine(t: Type, name: Name): Sourcelike {
         const camelCaseName = modifySource(camelCase, name);
         const returnType =
-            this._tsFlowOptions.rawType === "json" ? "string" : "any";
+            this._tsFlowOptions.rawType === "json" ? "string" : this.anyType();
         return [
             "public static ",
             camelCaseName,
@@ -45,7 +48,15 @@ export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
     }
 
     protected get typeAnnotations(): JavaScriptTypeAnnotations {
-        return Object.assign({ never: ": never" }, tsFlowTypeAnnotations);
+        const a = this.anyType();
+        return Object.assign({ never: ": never" }, {
+            any: `: ${a}`,
+            anyArray: `: ${a}[]`,
+            anyMap: `: { [k: string]: ${a} }`,
+            string: ": string",
+            stringArray: ": string[]",
+            boolean: ": boolean",
+        });
     }
 
     protected emitModuleExports(): void {

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

@@ -40,6 +40,11 @@ export const tsFlowOptions = Object.assign({}, javaScriptOptions, {
         false,
     ),
     readonly: new BooleanOption("readonly", "Use readonly type members", false),
+    preferUnknown: new BooleanOption(
+        "prefer-unknown",
+        "Use unknown instead of any type",
+        false,
+    ),
 });
 
 export const typeScriptLanguageConfig = {

test/languages.ts

@@ -839,6 +839,7 @@ export const TypeScriptLanguage: Language = {
         { "acronym-style": "pascal" },
         { converters: "all-objects" },
         { readonly: "true" },
+        { "prefer-unknown": "true" },
     ],
     sourceFiles: ["src/language/TypeScript/index.ts"],
 };