Seal mustachio nodes (#3433)

Author: srawlins

lib/src/mustachio/parser.dart

@@ -420,8 +420,7 @@ class MustachioParser {
 }
 
 /// An interface for various types of node in a Mustache template.
-@sealed
-abstract class MustachioNode {
+sealed class MustachioNode {
   SourceSpan get span;
 }
 
@@ -434,7 +433,7 @@ mixin HasMultiNamedKey {
 
 /// A Text node, representing literal text.
 @immutable
-class Text implements MustachioNode {
+final class Text implements MustachioNode {
   final String content;
 
   @override
@@ -448,7 +447,7 @@ class Text implements MustachioNode {
 
 /// A Variable node, representing a variable to be resolved.
 @immutable
-class Variable with HasMultiNamedKey implements MustachioNode {
+final class Variable with HasMultiNamedKey implements MustachioNode {
   @override
   final List<String> key;
 
@@ -470,7 +469,7 @@ class Variable with HasMultiNamedKey implements MustachioNode {
 /// A Section node, representing either a Conditional Section, a Repeated
 /// Section, or a Value Section, possibly inverted.
 @immutable
-class Section with HasMultiNamedKey implements MustachioNode {
+final class Section with HasMultiNamedKey implements MustachioNode {
   @override
   final List<String> key;
 
@@ -493,7 +492,7 @@ class Section with HasMultiNamedKey implements MustachioNode {
 
 /// A Partial node, representing a partial to be resolved.
 @immutable
-class Partial implements MustachioNode {
+final class Partial implements MustachioNode {
   final String key;
 
   @override

lib/src/mustachio/renderer_base.dart

@@ -100,30 +100,29 @@ class Template {
 
     // Walk the Mustache syntax tree, looking for Partial nodes.
     while (nodeQueue.isNotEmpty) {
-      var node = nodeQueue.removeFirst();
-      if (node is Text) {
-        // Nothing to do.
-      } else if (node is Variable) {
-        // Nothing to do.
-      } else if (node is Section) {
-        nodeQueue.addAll(node.children);
-      } else if (node is Partial) {
-        var key = node.key;
-        if (!partials.containsKey(key)) {
-          partials[key] = await partialResolver(key);
-        }
-        var partialFile = partials[key]!;
-        if (!partialTemplates.containsKey(partialFile)) {
-          try {
-            var partialTemplate = await Template.parse(partialFile,
-                partialResolver: partialResolver,
-                partialTemplates: {...partialTemplates});
-            partialTemplates[partialFile] = partialTemplate;
-          } on FileSystemException catch (e) {
-            throw MustachioResolutionError(node.span.message(
-                'FileSystemException (${e.message}) when reading partial:'));
+      switch (nodeQueue.removeFirst()) {
+        case Text():
+          break;
+        case Variable():
+          break;
+        case Section(:var children):
+          nodeQueue.addAll(children);
+        case Partial(:var span, :var key):
+          if (!partials.containsKey(key)) {
+            partials[key] = await partialResolver(key);
+          }
+          var partialFile = partials[key]!;
+          if (!partialTemplates.containsKey(partialFile)) {
+            try {
+              var partialTemplate = await Template.parse(partialFile,
+                  partialResolver: partialResolver,
+                  partialTemplates: {...partialTemplates});
+              partialTemplates[partialFile] = partialTemplate;
+            } on FileSystemException catch (e) {
+              throw MustachioResolutionError(span.message(
+                  'FileSystemException (${e.message}) when reading partial:'));
+            }
           }
-        }
       }
     }
 
@@ -218,19 +217,20 @@ abstract class RendererBase<T extends Object?> {
   /// Renders a block of Mustache template, the [ast], into [sink].
   void renderBlock(List<MustachioNode> ast) {
     for (var node in ast) {
-      if (node is Text) {
-        write(node.content);
-      } else if (node is Variable) {
-        var content = getFields(node);
-        if (node.escape) {
-          write(htmlEscape.convert(content));
-        } else {
-          write(content);
-        }
-      } else if (node is Section) {
-        section(node);
-      } else if (node is Partial) {
-        partial(node);
+      switch (node) {
+        case Text():
+          write(node.content);
+        case Variable():
+          var content = getFields(node);
+          if (node.escape) {
+            write(htmlEscape.convert(content));
+          } else {
+            write(content);
+          }
+        case Section():
+          section(node);
+        case Partial():
+          partial(node);
       }
     }
   }

tool/mustachio/codegen_aot_compiler.dart

@@ -442,15 +442,16 @@ class _BlockCompiler {
 
   Future<void> _compile(List<MustachioNode> syntaxTree) async {
     for (var node in syntaxTree) {
-      if (node is Text) {
-        _writeText(node.content);
-      } else if (node is Variable) {
-        var variableLookup = _lookUpGetter(node);
-        _writeGetter(variableLookup, escape: node.escape);
-      } else if (node is Section) {
-        await _compileSection(node);
-      } else if (node is Partial) {
-        await _compilePartial(node);
+      switch (node) {
+        case Text():
+          _writeText(node.content);
+        case Variable():
+          var variableLookup = _lookUpGetter(node);
+          _writeGetter(variableLookup, escape: node.escape);
+        case Section():
+          await _compileSection(node);
+        case Partial():
+          await _compilePartial(node);
       }
     }
   }