feat(typescript): Support interface heritage

Support for interfaces extending other interfaces, bi-directionally.
Also optionally merge object intersections into single self-contained types, defaulting to true for JSON Schema and Open API.

fix #15
fix #35

Author: grantila

lib/bin/typeconv.ts

@@ -148,6 +148,15 @@ const oppaInstance =
 		description: "Removes all annotations (descriptions, comments, ...)",
 		default: false,
 	} )
+	.add( {
+		name: 'merge-objects',
+		type: 'boolean',
+		description: [
+			"When simplifying the types, merge intersections of objects",
+			"into single self-contained objects.",
+			"This defaults to true when converting to JSON Schema/OpenAPI."
+		],
+	} )
 
 	.group( {
 		name: "TypeScript",
@@ -403,6 +412,7 @@ const {
 	"output-directory": outputDirectory,
 	"output-extension": outputExtension,
 	"strip-annotations": doStripAnnotations,
+	"merge-objects": mergeObjects,
 
 	// TypeScript
 	"ts-declaration": tsDeclaration,
@@ -464,6 +474,7 @@ if ( !ensureType< FromTsOptions[ 'nonExported' ] >(
 ) )
 	throw new Error( );
 
+const mergeObjectsDefault = toType === 'jsc' || toType === 'oapi';
 
 if ( !ensureType<
 		'ignore' | 'hoist' | 'dot' | 'underscore' | 'reconstruct-all'
@@ -578,6 +589,7 @@ const getWriter = ( ): Writer =>
 				!doStripAnnotations ? { } :
 				{ map: ( node => stripAnnotations( node ) ) }
 			),
+			mergeObjects: mergeObjects ?? mergeObjectsDefault,
 			cwd,
 			shortcut,
 		}

lib/converter.ts

@@ -82,6 +82,14 @@ export interface ConvertOptions
 	 */
 	simplify?: boolean;
 
+	/**
+	 * When simplifying (which is implied by this option), and-types of objects
+	 * will be merged into one self-contained object.
+	 * This is useful for type systems that don't treat object intersections the
+	 * same way e.g. TypeScript does.
+	 */
+	mergeObjects?: boolean;
+
 	/**
 	 * Custom map function for transforming each type after it has been
 	 * converted *from* the source type (and after it has been simplified),
@@ -303,7 +311,7 @@ export function makeConverter(
 			const simplifiedDoc =
 				options?.simplify === false
 				? doc
-				: simplify( doc );
+				: simplify( doc, { mergeObjects: options?.mergeObjects } );
 
 			const { map, filter, transform } = options ?? { };
 

lib/tests/__snapshots__/ts-to-json-schema.test.ts.snap

@@ -0,0 +1,83 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`ts-to-json-schema interface heritage 1`] = `
+"{
+  "definitions": {
+    "Foo": {
+      "type": "object",
+      "properties": {
+        "b": {
+          "type": "string",
+          "title": "Bar.b"
+        },
+        "f": {
+          "type": "number",
+          "title": "Foo.f"
+        }
+      },
+      "required": [
+        "b",
+        "f"
+      ],
+      "additionalProperties": false,
+      "title": "Foo, Bar"
+    },
+    "Bar": {
+      "type": "object",
+      "properties": {
+        "b": {
+          "type": "string",
+          "title": "Bar.b"
+        }
+      },
+      "required": [
+        "b"
+      ],
+      "additionalProperties": false,
+      "title": "Bar"
+    }
+  },
+  "$comment": "Generated by core-types-json-schema (https://github.com/grantila/core-types-json-schema) on behalf of typeconv (https://github.com/grantila/typeconv)"
+}"
+`;
+
+exports[`ts-to-json-schema type intersection 1`] = `
+"{
+  "definitions": {
+    "Foo": {
+      "type": "object",
+      "properties": {
+        "b": {
+          "type": "string",
+          "title": "Bar.b"
+        },
+        "f": {
+          "type": "number",
+          "title": "f"
+        }
+      },
+      "required": [
+        "b",
+        "f"
+      ],
+      "additionalProperties": false,
+      "title": "Foo, Bar"
+    },
+    "Bar": {
+      "type": "object",
+      "properties": {
+        "b": {
+          "type": "string",
+          "title": "Bar.b"
+        }
+      },
+      "required": [
+        "b"
+      ],
+      "additionalProperties": false,
+      "title": "Bar"
+    }
+  },
+  "$comment": "Generated by core-types-json-schema (https://github.com/grantila/core-types-json-schema) on behalf of typeconv (https://github.com/grantila/typeconv)"
+}"
+`;

lib/tests/ts-to-json-schema.test.ts

@@ -0,0 +1,64 @@
+import { expect, describe, it } from "@jest/globals"
+
+import {
+	makeConverter,
+	getTypeScriptReader,
+	getJsonSchemaWriter,
+} from '../index.js'
+
+
+describe( 'ts-to-json-schema', ( ) =>
+{
+    // https://github.com/grantila/typeconv/issues/15
+    // https://github.com/grantila/typeconv/issues/35
+	it( 'interface heritage', async ( ) =>
+	{
+		const input = `
+			interface Bar {
+				b: string;
+			}
+
+			export interface Foo extends Bar {
+				f: number;
+			}
+		`;
+
+		const { convert } = makeConverter(
+			getTypeScriptReader( ),
+			getJsonSchemaWriter( ),
+            {
+                mergeObjects: true,
+            }
+		);
+
+		const { data } = await convert( { data: input } );
+
+		expect( data ).toMatchSnapshot( );
+	} );
+
+    // https://github.com/grantila/typeconv/issues/35
+	it( 'type intersection', async ( ) =>
+	{
+		const input = `
+			type Bar = {
+				b: string;
+			}
+
+			export type Foo = Bar & {
+				f: number;
+			}
+		`;
+
+		const { convert } = makeConverter(
+			getTypeScriptReader( ),
+			getJsonSchemaWriter( ),
+            {
+                mergeObjects: true,
+            }
+		);
+
+		const { data } = await convert( { data: input } );
+
+		expect( data ).toMatchSnapshot( );
+	} );
+} );

package.json

@@ -62,11 +62,11 @@
     "already": "^3.4.1",
     "awesome-code-frame": "^1.1.0",
     "chalk": "^5.2.0",
-    "core-types": "^3.0.0",
+    "core-types": "^3.1.0",
     "core-types-graphql": "^3.0.0",
     "core-types-json-schema": "^2.1.0",
     "core-types-suretype": "^3.2.0",
-    "core-types-ts": "^4.0.1",
+    "core-types-ts": "^4.1.0",
     "globby": "^13.1.3",
     "js-yaml": "^4.1.0",
     "oppa": "^0.4.0",