Mustachio: Add getProperty(), and end-to-end Renderer test (#2442)

Mustachio: Add property getters to Property, and end-to-end Renderer test

This includes some unorthodox tests: I've added a package in
`testing/mustachio`, complete with a pubspec.yaml and a build.yaml. These are
required in order to test the runtime behavior of generated code; in order to
make assertions on the generated code (not its String content, but its runtime
properties), it must be generated with public classes (the default is private).
In order to pass a configuration to the Builder, I need a build.yaml separate
from dartdoc's.

In order to import `testing/mustachio/lib/foo.renderers.dart`, and resolve that
library's reference to `package:testing_mustachio/foo.dart`, I need to add
`testing_mustachio` to `dev_dependencies`.

In order to reference the builders from the testing package, the builder code
needed to move from `tool/mustachio/` to `lib/src/mustachio/`.

The generated code now always references the library that generated it, on the
assumption that it needs types from that file. This is not necessarily correct,
but is a decent approximation until we start using code_builder.

RendererBase now needs to know about the renderer of the parent context type,
so it gets a new field.

Property and each renderer's propertyMap gets corrected code; the runtime tests
revealed some runtime type bugs.

Author: srawlins

build.yaml

@@ -16,8 +16,26 @@ targets:
     sources:
       - tool/builder.dart
       - tool/mustachio/builder.dart
+  testing:
+    sources:
+      exclude:
+        - tool/builder.dart
+        - tool/mustachio/builder.dart
+    builders:
+      dartdoc|mustachio_builder:
+        enabled: true
+        generate_for:
+          - test/mustachio/foo.dart
+        options:
+          rendererClassesArePublic: true
+      build_test:test_bootstrap:
+        enabled: false
+      build_version:build_version:
+        enabled: false
 
   $default:
+    dependencies:
+      - :testing
     sources:
       exclude:
         - tool/builder.dart

lib/src/generator/templates.renderers.dart

@@ -10,20 +10,62 @@ abstract class RendererBase<T> {
   /// The context object which this renderer can render.
   final T context;
 
+  /// The renderer of the parent context, if any, otherwise `null`.
+  final RendererBase parent;
+
   /// The output buffer into which [context] is rendered, using a template.
   final buffer = StringBuffer();
 
-  RendererBase(this.context);
+  RendererBase(this.context, this.parent);
 
   void write(String text) => buffer.write(text);
 
+  /// Returns the [Property] on this renderer named [name].
+  ///
+  /// If no property named [name] exists for this renderer, `null` is returned.
+  Property getProperty(String key);
+
+  /// Resolves [names] into one or more field accesses, returning the result as
+  /// a String.
+  ///
+  /// [names] may have multiple dot-separate names, and [names] may not be a
+  /// valid property of _this_ context type, in which the [parent] renderer is
+  /// referenced.
+  String getFields(List<String> names) {
+    if (names.length == 1 && names.single == '.') {
+      return context.toString();
+    }
+    var property = getProperty(names.first);
+    if (property != null) {
+      var value = property.getValue(context);
+      for (var name in names.skip(1)) {
+        if (property.getProperties().containsKey(name)) {
+          property = property.getProperties()[name];
+          value = property.getValue(value);
+        } else {
+          throw MustachioResolutionError(
+              'Failed to resolve ${names.join('.')} as a property '
+              'on ${context.runtimeType}');
+        }
+      }
+      return value.toString();
+    } else if (parent != null) {
+      return parent.getFields(names);
+    } else {
+      throw MustachioResolutionError(
+          'Failed to resolve ${names.first} as a property '
+          'on any types in the current context');
+    }
+  }
+
   /// Renders a block of Mustache template, the [ast], into [buffer].
   void renderBlock(List<MustachioNode> ast) {
     for (var node in ast) {
       if (node is Text) {
         write(node.content);
       } else if (node is Variable) {
-        // TODO(srawlins): Implement.
+        var content = getFields(node.key);
+        write(content);
       } else if (node is Section) {
         section(node);
       } else if (node is Partial) {
@@ -60,3 +102,10 @@ class Property<T> {
 
   Property({@required this.getValue, this.getProperties, this.getBool});
 }
+
+/// An error indicating that a renderer failed to resolve a key.
+class MustachioResolutionError extends Error {
+  String message;
+
+  MustachioResolutionError(this.message);
+}

lib/src/mustachio/renderer_base.dart

@@ -90,7 +90,7 @@ class Bar {}
       expect(
           generatedContent,
           contains(
-              'String _render_FooBase(FooBase context, List<MustachioNode> ast)'));
+              'String _render_FooBase(FooBase context, List<MustachioNode> ast,'));
       // The renderer class for Foo
       expect(generatedContent,
           contains('class _Renderer_FooBase extends RendererBase<FooBase>'));
@@ -101,7 +101,7 @@ class Bar {}
       expect(
           generatedContent,
           contains(
-              'String _render_Object(Object context, List<MustachioNode> ast) {'));
+              'String _render_Object(Object context, List<MustachioNode> ast,'));
       // The renderer class for Object
       expect(generatedContent,
           contains('class _Renderer_Object extends RendererBase<Object> {'));
@@ -120,13 +120,13 @@ class Bar {}
 
     test('with a property map', () {
       expect(generatedContent,
-          contains('static Map<String, Property<Foo>> propertyMap() => {'));
+          contains('static Map<String, Property> propertyMap() => {'));
     });
 
     test('with a property map with a String property', () {
       expect(generatedContent, contains('''
         's1': Property(
-          getValue: (Foo c) => c.s1,
+          getValue: (Object c) => (c as Foo).s1,
           getProperties: _Renderer_String.propertyMap,
         ),
 '''));
@@ -139,9 +139,9 @@ class Bar {}
     test('with a property map with a bool property', () {
       expect(generatedContent, contains('''
         'b1': Property(
-          getValue: (Foo c) => c.b1,
+          getValue: (Object c) => (c as Foo).b1,
           getProperties: _Renderer_bool.propertyMap,
-          getBool: (Foo c) => c.b1 == true,
+          getBool: (Object c) => (c as Foo).b1 == true,
         ),
 '''));
     });
@@ -191,7 +191,7 @@ import 'package:mustachio/annotations.dart';
       expect(
           generatedContent,
           contains(
-              'String renderFoo<T>(Foo<T> context, List<MustachioNode> ast)'));
+              'String renderFoo<T>(Foo<T> context, List<MustachioNode> ast,'));
     });
 
     test('with a generic supertype type argument', () async {

test/mustachio/builder_test.dart

@@ -0,0 +1,9 @@
+@Renderer(#renderFoo, Context<Foo>())
+library dartdoc.testing.foo;
+
+import 'package:dartdoc/src/mustachio/annotations.dart';
+
+class Foo {
+  String s1 = 's1';
+  bool b1 = true;
+}