refactor(@angular/cli): avoid implicit undefined array defaults for @angular/build builders

Previously, all builder options that were of type array were
set to a default empty array even if there was no explicit default defined
within the schema. This can be problematic for options that have differing
behavior based on their presence such as runtime calculated defaults. The
implicit defaulting behavior was also not aligned with the generated schema
types which resulted in additional type safety and initialization regardless.
As a result, the implicit behavior was effectively redundant in most cases.
Since this change could be breaking for third-party builders, the removal of
this behavior is currently limited to the `@angular/build` package.

Author: clydin

goldens/public-api/angular_devkit/core/index.api.md

@@ -18,6 +18,9 @@ import { ValidateFunction } from 'ajv';
 // @public (undocumented)
 function addUndefinedDefaults(value: JsonValue, _pointer: JsonPointer, schema?: JsonSchema): JsonValue;
 
+// @public (undocumented)
+function addUndefinedObjectDefaults(value: JsonValue, _pointer: JsonPointer, schema?: JsonSchema): JsonValue;
+
 // @public
 class AliasHost<StatsT extends object = {}> extends ResolverHost<StatsT> {
     // (undocumented)
@@ -1297,6 +1300,7 @@ class TransformLogger extends Logger {
 
 declare namespace transforms {
     export {
+        addUndefinedObjectDefaults,
         addUndefinedDefaults
     }
 }

modules/testing/builder/src/builder-harness.ts

@@ -104,7 +104,11 @@ export class BuilderHarness<T> {
       ...builderInfo,
     };
 
-    this.schemaRegistry.addPostTransform(json.schema.transforms.addUndefinedDefaults);
+    if (builderInfo?.builderName?.startsWith('@angular/build:')) {
+      this.schemaRegistry.addPostTransform(json.schema.transforms.addUndefinedObjectDefaults);
+    } else {
+      this.schemaRegistry.addPostTransform(json.schema.transforms.addUndefinedDefaults);
+    }
   }
 
   private resolvePath(path: string): string {

packages/angular/build/src/builders/application/tests/setup.ts

@@ -13,7 +13,7 @@ import { Schema } from '../schema';
 export * from '../../../../../../../modules/testing/builder/src';
 
 export const APPLICATION_BUILDER_INFO = Object.freeze({
-  name: '@angular-devkit/build-angular:application',
+  name: '@angular/build:application',
   schemaPath: __dirname + '/../schema.json',
 });
 

packages/angular/cli/src/command-builder/architect-base-command-module.ts

@@ -52,10 +52,16 @@ export abstract class ArchitectBaseCommandModule<T extends object>
       return this.onMissingTarget(e.message);
     }
 
+    const isAngularBuild = builderName.startsWith('@angular/build:');
+
     const { logger } = this.context;
-    const run = await this.getArchitect().scheduleTarget(target, options as json.JsonObject, {
-      logger,
-    });
+    const run = await this.getArchitect(isAngularBuild).scheduleTarget(
+      target,
+      options as json.JsonObject,
+      {
+        logger,
+      },
+    );
 
     const analytics = isPackageNameSafeForAnalytics(builderName)
       ? await this.getAnalytics()
@@ -150,13 +156,17 @@ export abstract class ArchitectBaseCommandModule<T extends object>
   }
 
   private _architect: Architect | undefined;
-  protected getArchitect(): Architect {
+  protected getArchitect(skipUndefinedArrayTransform: boolean): Architect {
     if (this._architect) {
       return this._architect;
     }
 
     const registry = new json.schema.CoreSchemaRegistry();
-    registry.addPostTransform(json.schema.transforms.addUndefinedDefaults);
+    if (skipUndefinedArrayTransform) {
+      registry.addPostTransform(json.schema.transforms.addUndefinedObjectDefaults);
+    } else {
+      registry.addPostTransform(json.schema.transforms.addUndefinedDefaults);
+    }
     registry.useXDeprecatedProvider((msg) => this.context.logger.warn(msg));
 
     const architectHost = this.getArchitectHost();

packages/angular_devkit/core/src/json/schema/transforms.ts

@@ -11,10 +11,27 @@ import { JsonPointer } from './interface';
 import { JsonSchema } from './schema';
 import { getTypesOfSchema } from './utility';
 
+export function addUndefinedObjectDefaults(
+  value: JsonValue,
+  _pointer: JsonPointer,
+  schema?: JsonSchema,
+): JsonValue {
+  return transformUndefined(value, _pointer, schema, true);
+}
+
 export function addUndefinedDefaults(
   value: JsonValue,
   _pointer: JsonPointer,
   schema?: JsonSchema,
+): JsonValue {
+  return transformUndefined(value, _pointer, schema, false);
+}
+
+function transformUndefined(
+  value: JsonValue,
+  _pointer: JsonPointer,
+  schema?: JsonSchema,
+  onlyObjects?: boolean,
 ): JsonValue {
   if (typeof schema === 'boolean' || schema === undefined) {
     return value;
@@ -45,7 +62,7 @@ export function addUndefinedDefaults(
     return value;
   }
 
-  if (type === 'array') {
+  if (!onlyObjects && type === 'array') {
     return value == undefined ? [] : value;
   }
 
@@ -94,7 +111,7 @@ export function addUndefinedDefaults(
           });
 
         if (adjustedSchema && isJsonObject(adjustedSchema)) {
-          newValue[propName] = addUndefinedDefaults(value, _pointer, adjustedSchema);
+          newValue[propName] = transformUndefined(value, _pointer, adjustedSchema, onlyObjects);
         }
       }
     }