feat(@angular-devkit/schematics): returning a rule chains it

Instead of having to call the rule (which is an anti-pattern), the system now understands
that returning a Rule should chain it to this current Rule.

There is no way to do some pattern (like read a file to select between two Rules) without
this feature.

packages/_/devkit/package/factory.ts

@@ -8,7 +8,6 @@
 import { JsonAstObject, JsonValue, parseJsonAst } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   Tree,
   UpdateRecorder,
   apply,
@@ -88,18 +87,16 @@ export default function (options: Schema): Rule {
              .replace(/-/g, '_');
 
   // Verify if we need to create a full project, or just add a new schematic.
-  return (tree: Tree, context: SchematicContext) => {
-    const source = apply(url('./project-files'), [
-      template({
-        ...options as object,
-        dot: '.',
-        path,
-      }),
-    ]);
+  const source = apply(url('./project-files'), [
+    template({
+      ...options as object,
+      dot: '.',
+      path,
+    }),
+  ]);
 
-    return chain([
-      mergeWith(source),
-      addPackageToMonorepo(options, path),
-    ])(tree, context);
-  };
+  return chain([
+    mergeWith(source),
+    addPackageToMonorepo(options, path),
+  ]);
 }

packages/angular/pwa/pwa/index.ts

@@ -33,7 +33,7 @@ function addServiceWorker(options: PwaOptions): Rule {
     };
     delete swOptions.title;
 
-    return externalSchematic('@schematics/angular', 'service-worker', swOptions)(host, context);
+    return externalSchematic('@schematics/angular', 'service-worker', swOptions);
   };
 }
 
@@ -153,7 +153,7 @@ function addManifestToAssetsConfig(options: PwaOptions) {
 }
 
 export default function (options: PwaOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option "project" is required.');
@@ -186,6 +186,6 @@ export default function (options: PwaOptions): Rule {
       ])),
       updateIndexFile(options),
       addManifestToAssetsConfig(options),
-    ])(host, context);
+    ]);
   };
 }

packages/angular_devkit/schematics/src/engine/interface.ts

@@ -217,4 +217,4 @@ export type AsyncFileOperator = (tree: FileEntry) => Observable<FileEntry | null
  * know which types is the schematic or collection metadata, as they are both tooling specific.
  */
 export type Source = (context: SchematicContext) => Tree | Observable<Tree>;
-export type Rule = (tree: Tree, context: SchematicContext) => Tree | Observable<Tree> | void;
+export type Rule = (tree: Tree, context: SchematicContext) => Tree | Observable<Tree> | Rule | void;

packages/angular_devkit/schematics/src/rules/call.ts

@@ -83,6 +83,9 @@ export function callRule(rule: Rule,
       return observableOf(inputTree);
     } else if (TreeSymbol in result) {
       return observableOf(result as Tree);
+    } else if (typeof result == 'function') {
+      // This is considered a Rule, chain the rule and return its output.
+      return callRule(result, input, context);
     } else if (isObservable(result)) {
       const obs = result as Observable<Tree>;
 

packages/schematics/angular/app-shell/index.ts

@@ -176,7 +176,7 @@ function addUniversalTarget(options: AppShellOptions): Rule {
     delete universalOptions.index;
     delete universalOptions.sourceDir;
 
-    return schematic('universal', universalOptions)(host, context);
+    return schematic('universal', universalOptions);
   };
 }
 

packages/schematics/angular/application/index.ts

@@ -350,6 +350,6 @@ export default function (options: ApplicationOptions): Rule {
           move(sourceDir),
         ]), MergeStrategy.Overwrite),
       schematic('e2e', e2eOptions),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/class/index.ts

@@ -52,6 +52,6 @@ export default function (options: ClassOptions): Rule {
       move(parsedPath.path),
     ]);
 
-    return branchAndMerge(mergeWith(templateSource))(host, context);
+    return branchAndMerge(mergeWith(templateSource));
   };
 }

packages/schematics/angular/component/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -127,7 +126,7 @@ function buildSelector(options: ComponentOptions, projectPrefix: string) {
 
 
 export default function(options: ComponentOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -165,6 +164,6 @@ export default function(options: ComponentOptions): Rule {
         addDeclarationToNgModule(options),
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/directive/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -103,7 +102,7 @@ function buildSelector(options: DirectiveOptions, projectPrefix: string) {
 }
 
 export default function (options: DirectiveOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -138,6 +137,6 @@ export default function (options: DirectiveOptions): Rule {
         addDeclarationToNgModule(options),
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/e2e/index.ts

@@ -146,7 +146,7 @@ function validateProjectName(projectName: string) {
 }
 
 export default function (options: E2eOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     validateProjectName(options.name);
 
     const workspace = getWorkspace(host);
@@ -171,6 +171,6 @@ export default function (options: E2eOptions): Rule {
           }),
           move(appDir),
         ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/enum/index.ts

@@ -53,6 +53,6 @@ export default function (options: EnumOptions): Rule {
       branchAndMerge(chain([
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/guard/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -28,7 +27,7 @@ import { Schema as GuardOptions } from './schema';
 
 
 export default function (options: GuardOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -56,6 +55,6 @@ export default function (options: GuardOptions): Rule {
       branchAndMerge(chain([
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/interface/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -26,7 +25,7 @@ import { Schema as InterfaceOptions } from './schema';
 
 
 export default function (options: InterfaceOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -56,6 +55,6 @@ export default function (options: InterfaceOptions): Rule {
       branchAndMerge(chain([
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/library/index.ts

@@ -257,6 +257,6 @@ export default function (options: LibraryOptions): Rule {
           context.addTask(new NodePackageInstallTask());
         }
       },
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/migrations/update-6/index.ts

@@ -786,6 +786,6 @@ export default function (): Rule {
 
         return host;
       },
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/module/index.ts

@@ -8,7 +8,6 @@
 import { basename, dirname, normalize, relative, strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -72,7 +71,7 @@ function addDeclarationToNgModule(options: ModuleOptions): Rule {
 }
 
 export default function (options: ModuleOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -106,6 +105,6 @@ export default function (options: ModuleOptions): Rule {
         addDeclarationToNgModule(options),
         mergeWith(templateSource),
       ])),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/pipe/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -87,7 +86,7 @@ function addDeclarationToNgModule(options: PipeOptions): Rule {
 }
 
 export default function (options: PipeOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -114,9 +113,11 @@ export default function (options: PipeOptions): Rule {
       move(parsedPath.path),
     ]);
 
-    return branchAndMerge(chain([
+    return branchAndMerge(
+      chain([
         addDeclarationToNgModule(options),
         mergeWith(templateSource),
-      ]))(host, context);
+      ]),
+    );
   };
 }

packages/schematics/angular/service-worker/index.ts

@@ -187,6 +187,6 @@ export default function (options: ServiceWorkerOptions): Rule {
       updateConfigFile(options),
       addDependencies(),
       updateAppModule(options),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/service/index.ts

@@ -8,7 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
   SchematicsException,
   Tree,
   apply,
@@ -25,7 +24,7 @@ import { buildDefaultPath } from '../utility/project';
 import { Schema as ServiceOptions } from './schema';
 
 export default function (options: ServiceOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
+  return (host: Tree) => {
     const workspace = getWorkspace(host);
     if (!options.project) {
       throw new SchematicsException('Option (project) is required.');
@@ -50,6 +49,6 @@ export default function (options: ServiceOptions): Rule {
       move(parsedPath.path),
     ]);
 
-    return mergeWith(templateSource)(host, context);
+    return mergeWith(templateSource);
   };
 }

packages/schematics/angular/universal/index.ts

@@ -251,6 +251,6 @@ export default function (options: UniversalOptions): Rule {
       updateConfigFile(options, tsConfigDirectory),
       wrapBootstrapCall(options),
       addServerTransition(options),
-    ])(host, context);
+    ]);
   };
 }

packages/schematics/angular/workspace/index.ts

@@ -8,8 +8,6 @@
 import { strings } from '@angular-devkit/core';
 import {
   Rule,
-  SchematicContext,
-  Tree,
   apply,
   mergeWith,
   template,
@@ -19,15 +17,12 @@ import { latestVersions } from '../utility/latest-versions';
 import { Schema as WorkspaceOptions } from './schema';
 
 export default function (options: WorkspaceOptions): Rule {
-  return (host: Tree, context: SchematicContext) => {
-
-    return mergeWith(apply(url('./files'), [
-      template({
-        utils: strings,
-        ...options,
-        'dot': '.',
-        latestVersions,
-      }),
-    ]))(host, context);
-  };
+  return mergeWith(apply(url('./files'), [
+    template({
+      utils: strings,
+      ...options,
+      'dot': '.',
+      latestVersions,
+    }),
+  ]));
 }

packages/schematics/package_update/all/index.ts

@@ -10,11 +10,11 @@ import { SchematicsUpdateSchema } from '../schema';
 
 
 export default function(options: SchematicsUpdateSchema): Rule {
-  return (tree: Tree, context: SchematicContext) => {
+  return (_tree: Tree, context: SchematicContext) => {
     return chain(
       context.schematic.collection.listSchematicNames()
         .filter(name => name != context.schematic.description.name)
         .map(name => schematic(name, options)),
-    )(tree, context);
+    );
   };
 }