Add Block + BlockBuilder, some utilities.

lib/code_builder.dart

@@ -8,12 +8,14 @@ export 'src/emitter.dart' show DartEmitter;
 export 'src/matchers.dart' show equalsDart;
 export 'src/specs/annotation.dart' show Annotation, AnnotationBuilder;
 export 'src/specs/class.dart' show Class, ClassBuilder;
-export 'src/specs/code.dart' show Code, StaticCode, ScopedCode;
+export 'src/specs/code.dart'
+    show Block, BlockBuilder, Code, StaticCode, ScopedCode;
 export 'src/specs/constructor.dart' show Constructor, ConstructorBuilder;
 export 'src/specs/directive.dart'
     show Directive, DirectiveType, DirectiveBuilder;
 export 'src/specs/expression.dart'
     show
+        AsCodeExpression,
         BinaryExpression,
         CodeExpression,
         Expression,

lib/src/emitter.dart

@@ -25,7 +25,7 @@ import 'visitors.dart';
 ///
 /// If [elements] is at least 2 elements, inserts [separator] delimiting them.
 @visibleForTesting
-void visitAll<T>(
+StringSink visitAll<T>(
   Iterable<T> elements,
   StringSink output,
   void visit(T element), [
@@ -36,14 +36,15 @@ void visitAll<T>(
   //
   // ... which would allocate more StringBuffer(s) for a one-time use.
   if (elements.isEmpty) {
-    return;
+    return output;
   }
   final iterator = elements.iterator..moveNext();
   visit(iterator.current);
   while (iterator.moveNext()) {
     output.write(separator);
     visit(iterator.current);
   }
+  return output;
 }
 
 class DartEmitter extends Object

lib/src/matchers.dart

@@ -19,7 +19,7 @@ String _dartfmt(String source) {
   } catch (_) {
     // Ignored on purpose, probably not exactly valid Dart code.
   } finally {
-    source = source.replaceAll('  ', ' ').replaceAll('\n', '').trim();
+    source = collapseWhitespace(source);
   }
   return source;
 }

lib/src/specs/code.dart

@@ -4,14 +4,20 @@
 
 library code_builder.src.specs.code;
 
+import 'package:built_value/built_value.dart';
+import 'package:built_collection/built_collection.dart';
 import 'package:meta/meta.dart';
 
 import '../allocator.dart';
 import '../base.dart';
+import '../emitter.dart';
 import '../visitors.dart';
 
+import 'expression.dart';
 import 'reference.dart';
 
+part 'code.g.dart';
+
 /// Returns a scoped symbol to [Reference], with an import prefix if needed.
 ///
 /// This is short-hand for [Allocator.allocate] in most implementations.
@@ -41,10 +47,40 @@ abstract class Code implements Spec {
   R accept<R>(covariant CodeVisitor<R> visitor, [R context]);
 }
 
+/// Represents blocks of statements of Dart code.
+abstract class Block implements Built<Block, BlockBuilder>, Spec {
+  factory Block([void updates(BlockBuilder b)]) = _$Block;
+
+  Block._();
+
+  @override
+  R accept<R>(covariant CodeVisitor<R> visitor, [R context]) {
+    return visitor.visitBlock(this, context);
+  }
+
+  BuiltList<Code> get statements;
+}
+
+abstract class BlockBuilder implements Builder<Block, BlockBuilder> {
+  factory BlockBuilder() = _$BlockBuilder;
+
+  BlockBuilder._();
+
+  /// Adds an [expression] to [statements].
+  ///
+  /// **NOTE**: Not all expressions are _useful_ statements.
+  void addExpression(Expression expression) {
+    statements.add(expression.asStatement());
+  }
+
+  ListBuilder<Code> statements = new ListBuilder<Code>();
+}
+
 /// Knowledge of different types of blocks of code in Dart.
 ///
 /// **INTERNAL ONLY**.
 abstract class CodeVisitor<T> implements SpecVisitor<T> {
+  T visitBlock(Block code, [T context]);
   T visitStaticCode(StaticCode code, [T context]);
   T visitScopedCode(ScopedCode code, [T context]);
 }
@@ -54,6 +90,14 @@ abstract class CodeEmitter implements CodeVisitor<StringSink> {
   @protected
   Allocator get allocator;
 
+  @override
+  visitBlock(Block block, [StringSink output]) {
+    output ??= new StringBuffer();
+    return visitAll<Code>(block.statements, output, (statement) {
+      statement.accept(this, output);
+    }, '\n');
+  }
+
   @override
   visitStaticCode(StaticCode code, [StringSink output]) {
     output ??= new StringBuffer();
@@ -77,6 +121,9 @@ class StaticCode implements Code {
   R accept<R>(CodeVisitor<R> visitor, [R context]) {
     return visitor.visitStaticCode(this, context);
   }
+
+  @override
+  String toString() => code;
 }
 
 /// Represents a [code] block that may require scoping.
@@ -89,4 +136,7 @@ class ScopedCode implements Code {
   R accept<R>(CodeVisitor<R> visitor, [R context]) {
     return visitor.visitScopedCode(this, context);
   }
+
+  @override
+  String toString() => code((ref) => ref.symbol);
 }

lib/src/specs/expression.dart

@@ -27,7 +27,12 @@ abstract class Expression implements Spec {
   R accept<R>(covariant ExpressionVisitor<R> visitor, [R context]);
 
   /// Returns the expression as a valid [Code] block.
-  Code asCode() => new _AsExpressionCode(this);
+  ///
+  /// Also see [asStatement].
+  Code asCode() => new AsCodeExpression(this, false);
+
+  /// Returns the expression asa valid [Code] block with a trailing `;`.
+  Code asStatement() => new AsCodeExpression(this, true);
 
   /// Returns the result of [this] `&&` [other].
   Expression and(Expression other) {
@@ -86,21 +91,30 @@ abstract class Expression implements Spec {
 }
 
 /// Represents a [code] block that wraps an [Expression].
-class _AsExpressionCode implements Code {
+class AsCodeExpression implements Code {
   final Expression code;
 
-  const _AsExpressionCode(this.code);
+  /// Whether this code should be considered a _statement_.
+  final bool isStatement;
+
+  @visibleForTesting
+  const AsCodeExpression(this.code, [this.isStatement = false]);
 
   @override
   R accept<R>(CodeVisitor<R> visitor, [R context]) {
-    return code.accept(visitor as ExpressionVisitor<R>, context);
+    return (visitor as ExpressionVisitor<R>)
+        .visitAsCodeExpression(this, context);
   }
+
+  @override
+  String toString() => code.toString();
 }
 
 /// Knowledge of different types of expressions in Dart.
 ///
 /// **INTERNAL ONLY**.
 abstract class ExpressionVisitor<T> implements SpecVisitor<T> {
+  T visitAsCodeExpression(AsCodeExpression code, [T context]);
   T visitBinaryExpression(BinaryExpression expression, [T context]);
   T visitCodeExpression(CodeExpression expression, [T context]);
   T visitInvokeExpression(InvokeExpression expression, [T context]);
@@ -113,6 +127,16 @@ abstract class ExpressionVisitor<T> implements SpecVisitor<T> {
 ///
 /// **INTERNAL ONLY**.
 abstract class ExpressionEmitter implements ExpressionVisitor<StringSink> {
+  @override
+  visitAsCodeExpression(AsCodeExpression expression, [StringSink output]) {
+    output ??= new StringBuffer();
+    expression.code.accept(this, output);
+    if (expression.isStatement) {
+      output.write(';');
+    }
+    return output;
+  }
+
   @override
   visitBinaryExpression(BinaryExpression expression, [StringSink output]) {
     output ??= new StringBuffer();

lib/src/specs/expression/invoke.dart

@@ -41,6 +41,10 @@ class InvokeExpression extends Expression {
   R accept<R>(ExpressionVisitor<R> visitor, [R context]) {
     return visitor.visitInvokeExpression(this, context);
   }
+
+  @override
+  String toString() =>
+      '${type ?? ''} $target($positionalArguments, $namedArguments)';
 }
 
 enum InvokeExpressionType {

lib/src/specs/expression/literal.dart

@@ -95,6 +95,9 @@ class LiteralExpression extends Expression {
   R accept<R>(ExpressionVisitor<R> visitor, [R context]) {
     return visitor.visitLiteralExpression(this, context);
   }
+
+  @override
+  String toString() => literal;
 }
 
 class LiteralListExpression extends Expression {
@@ -108,6 +111,9 @@ class LiteralListExpression extends Expression {
   R accept<R>(ExpressionVisitor<R> visitor, [R context]) {
     return visitor.visitLiteralListExpression(this, context);
   }
+
+  @override
+  String toString() => '[${values.map(literal).join(', ')}]';
 }
 
 class LiteralMapExpression extends Expression {
@@ -127,4 +133,7 @@ class LiteralMapExpression extends Expression {
   R accept<R>(ExpressionVisitor<R> visitor, [R context]) {
     return visitor.visitLiteralMapExpression(this, context);
   }
+
+  @override
+  String toString() => '{$values}';
 }

test/specs/code/statement_test.dart

@@ -0,0 +1,38 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:code_builder/code_builder.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('should emit a block of code', () {
+    expect(
+      new Block((b) => b.statements.addAll([
+            const Code('if (foo) {'),
+            const Code('  print(true);'),
+            const Code('}'),
+          ])),
+      equalsDart(r'''
+        if (foo) {
+          print(true);
+        }
+      '''),
+    );
+  });
+
+  test('should emit a block of code including expressions', () {
+    expect(
+      new Block((b) => b.statements.addAll([
+            const Code('if (foo) {'),
+            refer('print')([literalTrue]).asStatement(),
+            const Code('}'),
+          ])),
+      equalsDart(r'''
+        if (foo) {
+          print(true);
+        }
+      '''),
+    );
+  });
+}