Migrate runtime renderer to NNBD (#2849)

* squash from chain merges

* Things seem to work now, if not completely cleanly.

* Get runtime_renderer_render_test ready for NNBD strong mode, fix a few more problems

* deconfuse github

* add todo

Author: jcollins-g

lib/src/generator/templates.runtime_renderers.dart

@@ -269,10 +269,9 @@ abstract class RendererBase<T extends Object?> {
 
     // If this section is not a conditional or repeated section, it is a value
     // section, regardless of type.
-    var isNullValue = property.isNullValue!;
-    if (node.invert && isNullValue(context)) {
+    if (node.invert && property.isNullValue(context)) {
       renderBlock(node.children);
-    } else if (!node.invert && !isNullValue(context)) {
+    } else if (!node.invert && !property.isNullValue(context)) {
       property.renderValue!(context, this, node.children, sink);
     }
   }
@@ -288,17 +287,17 @@ abstract class RendererBase<T extends Object?> {
   }
 }
 
-String renderSimple(
-    Object context, List<MustachioNode> ast, Template template, StringSink sink,
+String renderSimple(Object? context, List<MustachioNode> ast, Template template,
+    StringSink sink,
     {required RendererBase<Object> parent, required Set<String> getters}) {
   var renderer = SimpleRenderer(context, parent, template, sink, getters);
   renderer.renderBlock(ast);
   return renderer.sink.toString();
 }
 
-class SimpleRenderer extends RendererBase<Object> {
+class SimpleRenderer extends RendererBase<Object?> {
   SimpleRenderer(
-    Object context,
+    Object? context,
     RendererBase<Object> parent,
     Template template,
     StringSink sink,
@@ -356,7 +355,7 @@ class Property<T> {
   final Iterable<void> Function(
       T, RendererBase<T>, List<MustachioNode>, StringSink)? renderIterable;
 
-  final bool Function(T)? isNullValue;
+  final bool Function(T) isNullValue;
 
   final void Function(T, RendererBase<T>, List<MustachioNode>, StringSink)?
       renderValue;
@@ -366,8 +365,11 @@ class Property<T> {
       required this.renderVariable,
       this.getBool,
       this.renderIterable,
-      this.isNullValue,
-      this.renderValue});
+      // TODO(jcollins-g): consider making this required or emitting warnings
+      // if called on a non-nullable?
+      bool Function(T)? isNullValue,
+      this.renderValue})
+      : isNullValue = (isNullValue ?? (_) => false);
 
   String renderSimpleVariable(
       T c, List<String> remainingNames, String typeString) {

lib/src/mustachio/renderer_base.dart

@@ -1,5 +1,3 @@
-// @dart=2.9
-
 @Renderer.forTest(#renderFoo, Context<Foo>(), 'foo',
     visibleTypes: {Property1, Property2, Property3})
 @Renderer.forTest(#renderBar, Context<Bar>(), 'bar')
@@ -9,43 +7,43 @@ library dartdoc.testing.foo;
 import 'package:dartdoc/src/mustachio/annotations.dart';
 
 class FooBase<T extends Object> {
-  T baz;
+  T? baz;
 }
 
 class Foo extends FooBase<Baz> {
-  String s1;
-  bool b1;
-  List<int> l1;
+  String s1 = '';
+  bool b1 = false;
+  List<int> l1 = [];
   @override
   // ignore: overridden_fields
-  Baz baz;
-  Property1 p1;
-  int length;
+  Baz? baz;
+  Property1? p1;
+  int? length;
 }
 
 class Bar {
-  Foo foo;
-  String s2;
-  Baz baz;
-  bool l1;
+  Foo? foo;
+  String? s2;
+  Baz? baz;
+  bool? l1;
 }
 
 class Baz {
-  Bar bar;
+  Bar? bar;
 }
 
 class Property1 {
-  Property2 p2;
+  Property2? p2;
 }
 
 class Property2 with Mixin1 {
-  String s;
+  String? s;
 }
 
 mixin Mixin1 {
-  Property3 p3;
+  Property3? p3;
 }
 
 class Property3 {
-  String s;
+  String? s;
 }