Break on lambda argument in method chain

changelog/@unreleased/pr-707.v2.yml

@@ -0,0 +1,16 @@
+type: improvement
+improvement:
+  description: "Break on lambda argument in method chain\n\n## Before this PR\nChained
+    calls involving lambda expressions don't line break, which conflicts with checkstyle
+    (at least the gradle-baseline checkstyle config)\n\n```java\nclass PalantirLambdaInliningPrefersBreak
+    {\n    void foo() {\n        return hello.read(txn -> {\n                    doSomeWork();\n
+    \                   doSomeMoreWork();\n                })\n                .chainedCall(()
+    -> {\n                    doSomeWork();\n                });\n    }\n}\n\n```\n\n##
+    After this PR\n\n```java\nclass PalantirLambdaInliningPrefersBreak {\n    void
+    foo() {\n        return hello\n                .read(txn -> {\n                    doSomeWork();\n
+    \                   doSomeMoreWork();\n                })\n                .chainedCall(()
+    -> {\n                    doSomeWork();\n                });\n    }\n}\n```\n\n##
+    Possible downsides?\n\U0001F937‍♂️  I've also added a test to show that non-chained
+    lambda calls don't include a line break"
+  links:
+  - https://github.com/palantir/palantir-java-format/pull/707

palantir-java-format/src/main/java/com/palantir/javaformat/java/JavaInputAstVisitor.java

@@ -35,6 +35,7 @@
 import static com.sun.source.tree.Tree.Kind.BLOCK;
 import static com.sun.source.tree.Tree.Kind.EXTENDS_WILDCARD;
 import static com.sun.source.tree.Tree.Kind.IF;
+import static com.sun.source.tree.Tree.Kind.LAMBDA_EXPRESSION;
 import static com.sun.source.tree.Tree.Kind.METHOD_INVOCATION;
 import static com.sun.source.tree.Tree.Kind.NEW_ARRAY;
 import static com.sun.source.tree.Tree.Kind.NEW_CLASS;
@@ -2783,7 +2784,11 @@ private void visitRegularDot(List<ExpressionTree> items, boolean needDot) {
         int length = needDot0 ? minLength : 0;
         for (ExpressionTree e : items) {
             if (needDot) {
-                if (length > minLength) {
+                // Also break if invoked with a lambda -- palantir-break-lambda-arg
+                // foo
+                //     .doSomething(() -> bar())
+                //     .doSomethingElse();
+                if (length > minLength || methodHasLambdaArg(e)) {
                     builder.breakOp(Break.builder()
                             .fillMode(FillMode.UNIFIED)
                             .flat("")
@@ -2808,6 +2813,14 @@ private void visitRegularDot(List<ExpressionTree> items, boolean needDot) {
         }
     }
 
+    private boolean methodHasLambdaArg(ExpressionTree e) {
+        if (!e.getKind().equals(METHOD_INVOCATION)) {
+            return false;
+        }
+        return ((MethodInvocationTree) e)
+                .getArguments().stream().anyMatch(argExpr -> argExpr.getKind().equals(LAMBDA_EXPRESSION));
+    }
+
     // avoid formattings like:
     //
     // when(

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/palantir-break-lambda-arg-no-chain.input

@@ -0,0 +1,8 @@
+class PalantirLambdaBreakChain {
+    void foo() {
+        return hello.read(txn -> {
+                    doSomeWork();
+                    doSomeMoreWork();
+                });
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/palantir-break-lambda-arg-no-chain.output

@@ -0,0 +1,8 @@
+class PalantirLambdaBreakChain {
+    void foo() {
+        return hello.read(txn -> {
+            doSomeWork();
+            doSomeMoreWork();
+        });
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/palantir-break-lambda-arg.input

@@ -0,0 +1,11 @@
+class PalantirLambdaBreakChain {
+    void foo() {
+        return hello.read(txn -> {
+                    doSomeWork();
+                    doSomeMoreWork();
+                })
+                .chainedCall(() -> {
+                    doSomeWork();
+                });
+    }
+}

palantir-java-format/src/test/resources/com/palantir/javaformat/java/testdata/palantir-break-lambda-arg.output

@@ -0,0 +1,12 @@
+class PalantirLambdaBreakChain {
+    void foo() {
+        return hello
+                .read(txn -> {
+                    doSomeWork();
+                    doSomeMoreWork();
+                })
+                .chainedCall(() -> {
+                    doSomeWork();
+                });
+    }
+}