Keep an annotated lambda parameter on its line

An annotation with arguments on a lambda parameter, such as
`(final var x, @SuppressWarnings("unused") var y) -> x + y`, forced a
line break after the annotation, so a statement that fits in 120
columns came out as four lines. visitLambdaExpression declared each
parameter with inlineAnnotationDirection, which answers VERTICAL, a
forced break, for any annotation that has arguments. That rule is for
local variable declarations, where the annotation above the type is the
wanted shape. Method parameters are declared with Direction.HORIZONTAL
and keep their annotations inline; lambda parameters now do the same.

Golden ojf-issue-101-annotated-lambda-parameters covers the broken
shape, a one-line input, two annotations, marker annotations, a block
body, a lambda too long for one line and one whose parameters do not
fit, with a method parameter and a local variable as controls. The JDK
21 and 25 sources format exactly as before: they have no lambda
parameter with an annotation that takes arguments.

Closes #101.

Author: abashev

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

@@ -1247,10 +1247,10 @@ protected void visitLambdaExpression(LambdaExpressionTree node, boolean statemen
                 token(",");
                 builder.breakOp(" ");
             }
-            visitVariables(
-                    ImmutableList.of(parameter),
-                    DeclarationKind.NONE,
-                    inlineAnnotationDirection(parameter.getModifiers()));
+            // A lambda parameter is a parameter: its annotations stay on its line, as a method parameter's do. The
+            // vertical direction, a forced break after an annotation with arguments, is for local variable
+            // declarations.
+            visitVariables(ImmutableList.of(parameter), DeclarationKind.NONE, Direction.HORIZONTAL);
             first = false;
         }
         if (parens) {

open-java-format/src/test/resources/com/palantir/javaformat/java/testdata/ojf-issue-101-annotated-lambda-parameters.input

@@ -0,0 +1,29 @@
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+class AnnotatedLambdaParameters {
+    BiFunction<Integer, Integer, Integer> withArgs =
+            (final var x,
+                    @SuppressWarnings("unused")
+                    var y) -> x + y;
+
+    Function<String, Integer> typed = ( @SuppressWarnings( "unused" )   String s )->s.length();
+
+    BiFunction<Integer, Integer, Integer> two = (@Deprecated @SuppressWarnings("unused")
+            var x, var y) -> x + y;
+
+    BiFunction<Integer, Integer, Integer> marker = (@Deprecated var x,
+        @Deprecated final var y) -> x + y;
+
+    Consumer<String> block = (@SuppressWarnings({"unused", "rawtypes"})
+            String s) -> { System.out.println(s); };
+
+    BiFunction<Integer, Integer, Integer> tooLongForOneLine = (@SuppressWarnings("unused") Integer first, @SuppressWarnings("unused") Integer second) -> first + second;
+
+    BiFunction<Integer, Integer, Integer> parametersDoNotFitOnOneLine = (@SuppressWarnings("unused") Integer firstParameterWithAVeryLongName, @SuppressWarnings("unused") Integer secondParameterWithAVeryLongName) -> firstParameterWithAVeryLongName + secondParameterWithAVeryLongName;
+
+    void method(@SuppressWarnings("unused") int y, @Deprecated int z) {
+        @SuppressWarnings("unchecked") Function<Object, String> local = o -> (String) o;
+    }
+}

open-java-format/src/test/resources/com/palantir/javaformat/java/testdata/ojf-issue-101-annotated-lambda-parameters.output

@@ -0,0 +1,30 @@
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+class AnnotatedLambdaParameters {
+    BiFunction<Integer, Integer, Integer> withArgs = (final var x, @SuppressWarnings("unused") var y) -> x + y;
+
+    Function<String, Integer> typed = (@SuppressWarnings("unused") String s) -> s.length();
+
+    BiFunction<Integer, Integer, Integer> two = (@Deprecated @SuppressWarnings("unused") var x, var y) -> x + y;
+
+    BiFunction<Integer, Integer, Integer> marker = (@Deprecated var x, @Deprecated final var y) -> x + y;
+
+    Consumer<String> block = (@SuppressWarnings({"unused", "rawtypes"}) String s) -> {
+        System.out.println(s);
+    };
+
+    BiFunction<Integer, Integer, Integer> tooLongForOneLine =
+            (@SuppressWarnings("unused") Integer first, @SuppressWarnings("unused") Integer second) -> first + second;
+
+    BiFunction<Integer, Integer, Integer> parametersDoNotFitOnOneLine =
+            (@SuppressWarnings("unused") Integer firstParameterWithAVeryLongName,
+                    @SuppressWarnings("unused") Integer secondParameterWithAVeryLongName) ->
+                    firstParameterWithAVeryLongName + secondParameterWithAVeryLongName;
+
+    void method(@SuppressWarnings("unused") int y, @Deprecated int z) {
+        @SuppressWarnings("unchecked")
+        Function<Object, String> local = o -> (String) o;
+    }
+}