Issue checkstyle#12809: Improve performance of lambda processing

nrmancuso · Mar 12, 2023 · 26f5021 · 26f5021
1 parent a684181
commit 26f5021
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Showing 2 changed files with 41 additions and 36 deletions.
diff --git a/src/main/java/com/puppycrawl/tools/checkstyle/JavaAstVisitor.java b/src/main/java/com/puppycrawl/tools/checkstyle/JavaAstVisitor.java
@@ -1297,21 +1297,7 @@ public DetailAstImpl visitExpressionList(JavaLanguageParser.ExpressionListContex
 
     @Override
     public DetailAstImpl visitExpression(JavaLanguageParser.ExpressionContext ctx) {
-        final DetailAstImpl expression = visit(ctx.expr());
-        DetailAstImpl exprRoot = createImaginary(TokenTypes.EXPR);
-        exprRoot.addChild(expression);
-
-        final int[] expressionsWithNoExprRoot = {
-            TokenTypes.CTOR_CALL,
-            TokenTypes.SUPER_CTOR_CALL,
-            TokenTypes.LAMBDA,
-        };
-
-        if (TokenUtil.isOfType(expression, expressionsWithNoExprRoot)) {
-            exprRoot = exprRoot.getFirstChild();
-        }
-
-        return exprRoot;
+        return buildExpressionNode(ctx.expr());
     }
 
     @Override
@@ -1495,7 +1481,21 @@ public DetailAstImpl visitSimpleMethodCall(JavaLanguageParser.SimpleMethodCallCo
 
     @Override
     public DetailAstImpl visitLambdaExp(JavaLanguageParser.LambdaExpContext ctx) {
-        return flattenedTree(ctx);
+        final DetailAstImpl lambda = create(ctx.LAMBDA());
+        lambda.addChild(visit(ctx.lambdaParameters()));
+
+        final DetailAstImpl rightHandLambdaChild;
+        if (ctx.block() != null) {
+            rightHandLambdaChild = visit(ctx.block());
+        }
+        else {
+            // Lambda expression child is built the same way that we build
+            // the initial expression node in visitExpression, i.e. with
+            // an imaginary EXPR node.
+            rightHandLambdaChild = buildExpressionNode(ctx.expr());
+        }
+        lambda.addChild(rightHandLambdaChild);
+        return lambda;
     }
 
     @Override
@@ -1627,14 +1627,6 @@ public DetailAstImpl visitTypeCastParameters(
         return typeType;
     }
 
-    @Override
-    public DetailAstImpl visitLambdaExpression(JavaLanguageParser.LambdaExpressionContext ctx) {
-        final DetailAstImpl lambda = create(ctx.LAMBDA());
-        lambda.addChild(visit(ctx.lambdaParameters()));
-        lambda.addChild(visit(ctx.lambdaBody()));
-        return lambda;
-    }
-
     @Override
     public DetailAstImpl visitSingleLambdaParam(JavaLanguageParser.SingleLambdaParamContext ctx) {
         return flattenedTree(ctx);
@@ -2160,6 +2152,30 @@ public DetailAstImpl visit(ParseTree tree) {
         return ast;
     }
 
+    /**
+     * Builds an expression node. This is used to build the root of an expression with
+     * an imaginary {@code EXPR} node.
+     *
+     * @param exprNode expression to build node for
+     * @return expression DetailAstImpl node
+     */
+    private DetailAstImpl buildExpressionNode(ParseTree exprNode) {
+        final DetailAstImpl expression = visit(exprNode);
+        DetailAstImpl exprRoot = createImaginary(TokenTypes.EXPR);
+        exprRoot.addChild(expression);
+
+        final int[] expressionsWithNoExprRoot = {
+            TokenTypes.CTOR_CALL,
+            TokenTypes.SUPER_CTOR_CALL,
+            TokenTypes.LAMBDA,
+        };
+
+        if (TokenUtil.isOfType(expression, expressionsWithNoExprRoot)) {
+            exprRoot = exprRoot.getFirstChild();
+        }
+        return exprRoot;
+    }
+
     /**
      * Used to swap and organize DetailAstImpl subtrees.
      */

diff --git a/src/main/resources/com/puppycrawl/tools/checkstyle/grammar/java/JavaLanguageParser.g4 b/src/main/resources/com/puppycrawl/tools/checkstyle/grammar/java/JavaLanguageParser.g4
@@ -720,18 +720,13 @@ expr
         | BAND_ASSIGN | BOR_ASSIGN | BXOR_ASSIGN | SR_ASSIGN | BSR_ASSIGN
         | SL_ASSIGN | MOD_ASSIGN)
       expr                                                                 #binOp
-    | lambdaExpression                                                     #lambdaExp
+    | lambdaParameters LAMBDA (expr | block)                               #lambdaExp
     ;
 
 typeCastParameters
     : typeType[true] (BAND typeType[true])*
     ;
 
-// Java8
-lambdaExpression
-    : lambdaParameters LAMBDA lambdaBody
-    ;
-
 // Java8
 lambdaParameters
     : id                                                                   #singleLambdaParam
@@ -743,12 +738,6 @@ multiLambdaParams
     : id (COMMA id)*
     ;
 
-// Java8
-lambdaBody
-    : expression
-    | block
-    ;
-
 primary
     : switchExpressionOrStatement                                          #switchPrimary
     | LPAREN expr RPAREN                                                   #parenPrimary