feat: jsii-reflect now renders union candidates sorted (#4005)

Sorting union members guarantees a uniform order is always presented, making it easier to visually compare assemblies (or pre-process them with `jsii-reflect` before using a textual `diff` tool). This also effects how `jsii-diff` compares assemblies, removing many false positives in breaking change detection.



---

By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

packages/jsii-diff/test/classes.test.ts

@@ -374,7 +374,7 @@ test.each([
   {
     oldDecl: 'name: string',
     newDecl: 'name: string | number',
-    error: /string \| number is not assignable to string/,
+    error: /number \| string is not assignable to string/,
   },
   {
     oldDecl: 'name: string | number',
@@ -413,12 +413,12 @@ test.each([
   {
     oldDecl: 'name: string',
     newDecl: 'name: string | number',
-    error: /changed to string \| number \(formerly string\)/,
+    error: /changed to number \| string \(formerly string\)/,
   },
   {
     oldDecl: 'name: string | number',
     newDecl: 'name: string',
-    error: /changed to string \(formerly string \| number\)/,
+    error: /changed to string \(formerly number \| string\)/,
   },
 ])(
   'cannot change a mutable class property type: %p to %p',

packages/jsii-diff/test/type-unions.test.ts

@@ -48,7 +48,7 @@ test('type unions in return structs can be narrowed', () =>
 
 test('type unions in return structs can not be widened', () =>
   expectError(
-    /some of string \| number \| boolean are not assignable to string \| number/,
+    /some of boolean \| number \| string are not assignable to number \| string/,
     `
     export interface Henk {
       readonly henk: string | number;
@@ -112,7 +112,7 @@ test('type unions in input structs can be widened', () =>
 
 test('type unions in input structs can not be narrowed', () =>
   expectError(
-    /string \| number is not assignable to string/,
+    /number \| string is not assignable to string/,
     `
     export interface Henk {
       readonly henk: string | number;

packages/jsii-reflect/lib/type-ref.ts

@@ -27,7 +27,9 @@ export class TypeReference {
       return `Map<string => ${this.mapOfType.toString()}>`;
     }
     if (this.unionOfTypes) {
-      return this.unionOfTypes.map((x) => x.toString()).join(' | ');
+      const union = this.unionOfTypes.map((x) => x.toString());
+      union.sort();
+      return union.join(' | ');
     }
 
     throw new Error('Invalid type reference');