Fix lambda expressions with no parameters and blocks as right side ex…

…pressions
Netflix-Skunkworks · Feb 2, 2017 · ddfdaa8 · ddfdaa8
1 parent 438623b
commit ddfdaa8
Show file tree

Hide file tree

Showing 4 changed files with 45 additions and 7 deletions.
diff --git a/rewrite/src/main/kotlin/com/netflix/rewrite/ast/Tree.kt b/rewrite/src/main/kotlin/com/netflix/rewrite/ast/Tree.kt
@@ -536,7 +536,7 @@ sealed class Tr : Serializable, Tree {
         data class Arrow(override val formatting: Formatting = Formatting.Empty, override val id: Long = id()): Tr()
 
         data class Parameters(val parenthesized: Boolean,
-                              val params: List<VariableDecls>,
+                              val params: List<Tree>, // Tr.VariableDecls or Tr.Empty
                               override val formatting: Formatting = Formatting.Empty,
                               override val id: Long = id()): Tr()
     }

diff --git a/rewrite/src/main/kotlin/com/netflix/rewrite/ast/visitor/TransformVisitor.kt b/rewrite/src/main/kotlin/com/netflix/rewrite/ast/visitor/TransformVisitor.kt
@@ -293,7 +293,7 @@ class TransformVisitor(val transformations: Iterable<AstTransform<*>>) : AstVisi
     }
 
     override fun visitLambda(lambda: Tr.Lambda): Tree {
-        val params = lambda.paramSet.params.mapIfNecessary { visit(it) as Tr.VariableDecls }
+        val params = lambda.paramSet.params.mapIfNecessary { visit(it) as Tree }
         val paramSet = if(params !== lambda.paramSet.params) {
             lambda.paramSet.copy(params = params)
         } else lambda.paramSet

diff --git a/rewrite/src/main/kotlin/com/netflix/rewrite/parse/OracleJdkParserVisitor.kt b/rewrite/src/main/kotlin/com/netflix/rewrite/parse/OracleJdkParserVisitor.kt
@@ -468,12 +468,34 @@ class OracleJdkParserVisitor(val path: Path, val source: String): TreePathScanne
     override fun visitLambdaExpression(node: LambdaExpressionTree, fmt: Formatting.Reified): Tree {
         val parenthesized = source[cursor] == '('
         skip("(")
+
+        val paramList = if(parenthesized && node.parameters.isEmpty()) {
+            listOf(Tr.Empty(format(sourceBefore(")"))))
+        } else {
+            node.parameters.convertAll(COMMA_DELIM, { if (parenthesized) sourceBefore(")") else "" })
+        }
+
+        val params = Tr.Lambda.Parameters(parenthesized, paramList)
+        val arrow = Tr.Lambda.Arrow(format(sourceBefore("->")))
+
+        val body = when(node.body) {
+            is JCTree.JCBlock -> {
+                // This compensates for a bug in the Oracle AST in which the startPos of JCBlock statements
+                // that are on the right side of lambda expressions evaluates at the start of the lambda expression.
+                // All other AST elements that can occur at the right side of lambda expressions correctly evluate startPos
+                // after the arrow.
+                val prefix = sourceBefore("{")
+                cursor--
+                val blockBody = node.body.convert<Tr.Block<*>>()
+                blockBody.changeFormatting(blockBody.formatting.withPrefix(prefix))
+            }
+            else -> node.body.convert<Tree>()
+        }
+
         return Tr.Lambda(
-                Tr.Lambda.Parameters(parenthesized, node.parameters.convertAll(COMMA_DELIM, {
-                    if(parenthesized) sourceBefore(")") else ""
-                })),
-                Tr.Lambda.Arrow(format(sourceBefore("->"))),
-                node.body.convert(),
+                params,
+                arrow,
+                body,
                 node.type(),
                 fmt
         )

diff --git a/rewrite/src/test/kotlin/com/netflix/rewrite/ast/LambdaTest.kt b/rewrite/src/test/kotlin/com/netflix/rewrite/ast/LambdaTest.kt
@@ -76,4 +76,20 @@ abstract class LambdaTest(p: Parser): Parser by p {
         assertEquals("list.stream().filter((s) -> s.isEmpty())",
                 a.classes[0].methods()[0].body!!.statements[0].printTrimmed())
     }
+
+    @Test
+    fun lambdaWithBlock() {
+        val a = parse("""
+            public class A {
+                Action a = ( ) -> { };
+            }
+
+            interface Action {
+                void call();
+            }
+        """)
+
+        val lambda = a.classes[0].fields()[0].vars[0].initializer!!
+        assertEquals("( ) -> { }", lambda.printTrimmed())
+    }
 }