Migrate the generated AOT renderers to null safety

test/mustachio/aot_compiler_render_test.dart

@@ -23,43 +23,43 @@ void main() {
   final sdk = p.dirname(p.dirname(Platform.resolvedExecutable));
   final fooCode = '''
 class FooBase<T extends Object> {
-  T baz;
+  T? baz;
 }
 
 class Foo extends FooBase<Baz> {
-String s1;
-bool b1;
-List<int> l1;
-@override
-Baz baz;
-Property1 p1;
+  String? s1 = '';
+  bool b1 = false;
+  List<int> l1 = [];
+  @override
+  Baz? baz;
+  Property1? p1;
 }
 
 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;
 }
 ''';
   InMemoryAssetWriter writer;
@@ -100,7 +100,7 @@ $mainCode
         'foo',
         Uri.directory(tempDir.path),
         packageUriRoot: Uri.directory(p.join(tempDir.path, 'lib')),
-        languageVersion: LanguageVersion(2, 9),
+        languageVersion: LanguageVersion(2, 12),
       )
     ]);
     var dartToolDir = Directory(p.join(tempDir.path, '.dart_tool'))
@@ -368,7 +368,7 @@ void main() {
               'Text {{#bar}}{{bar.foo.baz.bar.foo.s1}}{{/bar}}',
         },
         '_i1.Baz()..bar = (_i1.Bar()..foo = (_i1.Foo()..s1 = "hello"));'
-        'baz.bar.foo.baz = baz');
+        'baz.bar!.foo!.baz = baz');
     expect(output, equals('Text hello'));
   });
 
@@ -461,7 +461,7 @@ line 1, column 9 of package:foo/templates/html/foo.html: Failed to resolve '[s2]
             }, '_i1.Bar()..foo = _i1.Foo()'),
         throwsA(const TypeMatcher<MustachioResolutionError>()
             .having((e) => e.message, 'message', contains('''
-line 1, column 8 of package:foo/templates/html/bar.html: Failed to resolve 'x' on Bar while resolving [x] as a property chain on any types in the context chain: context0.foo, after first resolving 'foo' to a property on Foo
+line 1, column 8 of package:foo/templates/html/bar.html: Failed to resolve 'x' on Bar while resolving [x] as a property chain on any types in the context chain: context0.foo, after first resolving 'foo' to a property on Foo?
   ╷
 1 │ Text {{foo.x}}
   │        ^^^^^

test/mustachio/foo.aot_renderers_for_html.dart

@@ -7,7 +7,6 @@
 // the variable is not used; generally when the section is checking if a
 // non-bool, non-Iterable field is non-null.
 // ignore_for_file: unused_local_variable
-// @dart=2.9
 // ignore_for_file: non_constant_identifier_names, unnecessary_string_escapes
 
 import 'dart:convert' as _i2;
@@ -23,7 +22,7 @@ String renderFoo(_i1.Foo context0) {
   buffer.write('''
 
     s1: ''');
-  buffer.writeEscaped(context0.s1.toString());
+  buffer.writeEscaped(context0.s1?.toString());
   buffer.writeln();
   buffer.write('''
     b1? ''');
@@ -37,13 +36,11 @@ String renderFoo(_i1.Foo context0) {
   buffer.write('''
     l1:''');
   var context1 = context0.l1;
-  if (context1 != null) {
-    for (var context2 in context1) {
-      buffer.write('''item: ''');
-      buffer.writeEscaped(context2.toString());
-    }
+  for (var context2 in context1) {
+    buffer.write('''item: ''');
+    buffer.writeEscaped(context2.toString());
   }
-  if (context0.l1?.isEmpty ?? true) {
+  if (context0.l1.isEmpty) {
     buffer.write('''no items''');
   }
   buffer.writeln();
@@ -54,7 +51,7 @@ String renderFoo(_i1.Foo context0) {
     buffer.writeln();
     buffer.write('''
     Baz has a ''');
-    buffer.writeEscaped(context3.bar.s2.toString());
+    buffer.writeEscaped(context3.bar!.s2?.toString());
   }
   if (context0.baz == null) {
     buffer.write('''baz is null''');
@@ -91,7 +88,7 @@ String renderBaz(_i1.Baz context0) {
 }
 
 extension on StringBuffer {
-  void writeEscaped(String value) {
-    write(_i2.htmlEscape.convert(value));
+  void writeEscaped(String? value) {
+    write(_i2.htmlEscape.convert(value ?? ''));
   }
 }

test/mustachio/foo.aot_renderers_for_md.dart

@@ -7,7 +7,6 @@
 // the variable is not used; generally when the section is checking if a
 // non-bool, non-Iterable field is non-null.
 // ignore_for_file: unused_local_variable
-// @dart=2.9
 // ignore_for_file: non_constant_identifier_names, unnecessary_string_escapes
 
 import 'dart:convert' as _i2;
@@ -21,7 +20,7 @@ String renderFoo(_i1.Foo context0) {
   buffer.write('''
 
 s1: ''');
-  buffer.writeEscaped(context0.s1.toString());
+  buffer.writeEscaped(context0.s1?.toString());
   buffer.writeln();
   buffer.write('''
 b1? ''');
@@ -35,13 +34,11 @@ b1? ''');
   buffer.write('''
 l1:''');
   var context1 = context0.l1;
-  if (context1 != null) {
-    for (var context2 in context1) {
-      buffer.write('''item: ''');
-      buffer.writeEscaped(context2.toString());
-    }
+  for (var context2 in context1) {
+    buffer.write('''item: ''');
+    buffer.writeEscaped(context2.toString());
   }
-  if (context0.l1?.isEmpty ?? true) {
+  if (context0.l1.isEmpty) {
     buffer.write('''no items''');
   }
   buffer.writeln();
@@ -52,7 +49,7 @@ baz:''');
     buffer.writeln();
     buffer.write('''
 Baz has a ''');
-    buffer.writeEscaped(context3.bar.s2.toString());
+    buffer.writeEscaped(context3.bar!.s2?.toString());
   }
   if (context0.baz == null) {
     buffer.write('''baz is null''');
@@ -82,7 +79,7 @@ String renderBaz(_i1.Baz context0) {
 }
 
 extension on StringBuffer {
-  void writeEscaped(String value) {
-    write(_i2.htmlEscape.convert(value));
+  void writeEscaped(String? value) {
+    write(_i2.htmlEscape.convert(value ?? ''));
   }
 }

test/mustachio/foo.dart

@@ -11,7 +11,7 @@ class FooBase<T extends Object> {
 }
 
 class Foo extends FooBase<Baz> {
-  String s1 = '';
+  String? s1 = '';
   bool b1 = false;
   List<int> l1 = [];
   @override

test/mustachio/foo.runtime_renderers.dart

@@ -265,7 +265,7 @@ class Renderer_Foo extends RendererBase<Foo?> {
                   renderVariable: (CT_ c, Property<CT_> self,
                           List<String> remainingNames) =>
                       self.renderSimpleVariable(c, remainingNames, 'String'),
-                  isNullValue: (CT_ c) => false,
+                  isNullValue: (CT_ c) => c.s1 == null,
                   renderValue: (CT_ c, RendererBase<CT_> r,
                       List<MustachioNode> ast, StringSink sink) {
                     renderSimple(c.s1, ast, r.template, sink,

tool/mustachio/codegen_aot_compiler.dart

@@ -50,12 +50,12 @@ Future<String> compileTemplatesToRenderers(
         ..returns = refer('void')
         ..name = 'writeEscaped'
         ..requiredParameters.add(Parameter((b) => b
-          ..type = refer('String')
+          ..type = refer('String?')
           ..name = 'value'))
         ..body = refer('write').call([
           refer('htmlEscape', 'dart:convert')
               .property('convert')
-              .call([refer('value')])
+              .call([refer("value ?? ''")])
         ]).statement))));
   });
   return DartFormatter().format('''
@@ -68,7 +68,6 @@ Future<String> compileTemplatesToRenderers(
 // the variable is not used; generally when the section is checking if a
 // non-bool, non-Iterable field is non-null.
 // ignore_for_file: unused_local_variable
-// @dart=2.9
 // ignore_for_file: non_constant_identifier_names, unnecessary_string_escapes
 
 ${library.accept(DartEmitter.scoped(orderDirectives: true))}
@@ -154,8 +153,7 @@ class _AotCompiler {
 
   Future<List<Method>> _compileToRenderer() async {
     if (_contextStack.isEmpty) {
-      var contextName = 'context0';
-      var contextVariable = _VariableLookup(_contextType, contextName);
+      var contextVariable = _VariableLookup(_contextType, 'context0');
       _contextStack.push(contextVariable);
       _contextNameCounter++;
     }
@@ -361,16 +359,24 @@ class _BlockCompiler {
   Future<void> _compileRepeatedSection(
       _VariableLookup variableLookup, List<MustachioNode> block,
       {bool invert = false}) async {
+    var variableIsPotentiallyNullable =
+        typeSystem.isPotentiallyNullable(variableLookup.type);
     var variableAccess = variableLookup.name;
     if (invert) {
-      writeln('if ($variableAccess?.isEmpty ?? true) {');
+      if (variableIsPotentiallyNullable) {
+        writeln('if ($variableAccess?.isEmpty ?? true) {');
+      } else {
+        writeln('if ($variableAccess.isEmpty) {');
+      }
       await _compile(block);
       writeln('}');
     } else {
       var variableAccessResult = getNewContextName();
       writeln('var $variableAccessResult = $variableAccess;');
       var newContextName = getNewContextName();
-      writeln('if ($variableAccessResult != null) {');
+      if (variableIsPotentiallyNullable) {
+        writeln('if ($variableAccessResult != null) {');
+      }
       writeln('  for (var $newContextName in $variableAccessResult) {');
       // If [loopType] is something like `C<int>` where
       // `class C<T> implements Queue<Future<T>>`, we need the [ClassElement]
@@ -385,7 +391,9 @@ class _BlockCompiler {
       await _compile(block);
       _contextStack.pop();
       writeln('  }');
-      writeln('}');
+      if (variableIsPotentiallyNullable) {
+        writeln('}');
+      }
     }
   }
 
@@ -394,19 +402,27 @@ class _BlockCompiler {
       _VariableLookup variableLookup, List<MustachioNode> block,
       {bool invert = false}) async {
     var variableAccess = variableLookup.name;
+    var variableIsPotentiallyNullable =
+        typeSystem.isPotentiallyNullable(variableLookup.type);
     if (invert) {
       writeln('if ($variableAccess == null) {');
       await _compile(block);
       writeln('}');
     } else {
       var innerContextName = getNewContextName();
       writeln('var $innerContextName = $variableAccess;');
-      writeln('if ($innerContextName != null) {');
-      var innerContext = _VariableLookup(variableLookup.type, innerContextName);
+      if (variableIsPotentiallyNullable) {
+        writeln('if ($innerContextName != null) {');
+      }
+      var innerContext = _VariableLookup(
+          typeSystem.promoteToNonNull(variableLookup.type) as InterfaceType,
+          innerContextName);
       _contextStack.push(innerContext);
       await _compile(block);
       _contextStack.pop();
-      writeln('}');
+      if (variableIsPotentiallyNullable) {
+        writeln('}');
+      }
     }
   }
 
@@ -429,23 +445,31 @@ class _BlockCompiler {
         continue;
       }
 
-      var type = getter.returnType;
-      var contextChain = '${context.name}.$primaryName';
+      var type = getter.returnType as InterfaceType;
+      var contextChain = typeSystem.isPotentiallyNullable(context.type)
+          // This is imperfect; the idea is that in our templates, we may have
+          // `{{foo.bar.baz}}` and `foo.bar` may be nullably typed. Mustache
+          // (and Mustachio) does not have a null-aware property access
+          // operator, nor a null-check operator. This code translates
+          // `foo.bar.baz` to `foo.bar!.baz` for nullable `foo.bar`.
+          ? '${context.name}!.$primaryName'
+          : '${context.name}.$primaryName';
       var remainingNames = [...key.skip(1)];
       for (var secondaryKey in remainingNames) {
-        getter = (type as InterfaceType)
-            .lookUpGetter2(secondaryKey, type.element.library);
+        getter = type.lookUpGetter2(secondaryKey, type.element.library);
         if (getter == null) {
           throw MustachioResolutionError(node.keySpan.message(
               "Failed to resolve '$secondaryKey' on ${context.type} while "
               'resolving $remainingNames as a property chain on any types in '
               'the context chain: $contextChain, after first resolving '
               "'$primaryName' to a property on $type"));
         }
-        type = getter.returnType;
-        contextChain = '$contextChain.$secondaryKey';
+        contextChain = typeSystem.isPotentiallyNullable(type)
+            ? '$contextChain!.$secondaryKey'
+            : '$contextChain.$secondaryKey';
+        type = getter.returnType as InterfaceType;
       }
-      return _VariableLookup(type as InterfaceType, contextChain);
+      return _VariableLookup(type, contextChain);
     }
 
     var contextTypes = [
@@ -491,11 +515,12 @@ class _BlockCompiler {
   /// The result is HTML-escaped if [escape] is true.
   void _writeGetter(_VariableLookup variableLookup, {bool escape = true}) {
     var variableAccess = variableLookup.name;
-    if (escape) {
-      writeln('buffer.writeEscaped($variableAccess.toString());');
-    } else {
-      writeln('buffer.write($variableAccess.toString());');
-    }
+    var toString = typeSystem.isPotentiallyNullable(variableLookup.type)
+        ? '$variableAccess?.toString()'
+        : '$variableAccess.toString()';
+    writeln(escape
+        ? 'buffer.writeEscaped($toString);'
+        : 'buffer.write($toString);');
   }
 }