[PATCH v2] userdiff: improve java regex for generic return types

[Tassilo Horn <tsdh@gnu.org>]

Currently, the git diff hunk headers show the wrong method signature if the
method has an array or generic return type because the regex doesn't allow [],
or < and > in the return type.  Also, type parameter declarations couldn't be
matched.

Add several t4018 tests asserting the right hunk headers for increasingly
complex method signatures:

  public String[] secondMethod(String[] RIGHT)
  public List<String> secondMethod(String[] RIGHT)
  public <T> List<T> secondMethod(T[] RIGHT)
  public <AType, B> Map<AType, B> secondMethod(String[] RIGHT)
  public <AType, B> Map<AType, Map<B, B[]>> secondMethod(String[] RIGHT)

Signed-off-by: Tassilo Horn <tsdh@gnu.org>
---
 t/t4018/java-return-array    | 10 ++++++++++
 t/t4018/java-return-generic  | 10 ++++++++++
 t/t4018/java-return-generic2 | 10 ++++++++++
 t/t4018/java-return-generic3 | 10 ++++++++++
 t/t4018/java-return-generic4 | 10 ++++++++++
 userdiff.c                   | 10 +++++++++-
 6 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/java-return-array
 create mode 100644 t/t4018/java-return-generic
 create mode 100644 t/t4018/java-return-generic2
 create mode 100644 t/t4018/java-return-generic3
 create mode 100644 t/t4018/java-return-generic4

diff --git a/t/t4018/java-return-array b/t/t4018/java-return-array
new file mode 100644
index 0000000000..fc8882a5a9
--- /dev/null
+++ b/t/t4018/java-return-array
@@ -0,0 +1,10 @@
+class MyExample {
+    public void firstMethod() {
+        // Whatever...
+    }
+
+ public String[] secondMethod(String[] RIGHT) {
+        // Whatever...
+        return new; // ChangeMe
+    }
+}
diff --git a/t/t4018/java-return-generic b/t/t4018/java-return-generic
new file mode 100644
index 0000000000..7ea7bf8f07
--- /dev/null
+++ b/t/t4018/java-return-generic
@@ -0,0 +1,10 @@
+class MyExample {
+    public void firstMethod() {
+        // Whatever...
+    }
+
+    public List<String> secondMethod(String[] RIGHT) {
+        // Whatever...
+        return Arrays.asList("ChangeMe");
+    }
+}
diff --git a/t/t4018/java-return-generic2 b/t/t4018/java-return-generic2
new file mode 100644
index 0000000000..d2d2ab7f37
--- /dev/null
+++ b/t/t4018/java-return-generic2
@@ -0,0 +1,10 @@
+class MyExample {
+    public void firstMethod() {
+        // Whatever...
+    }
+
+    public <T> List<T> secondMethod(T[] RIGHT) {
+        // Whatever...
+        return (List<T>) Arrays.asList("ChangeMe");
+    }
+}
diff --git a/t/t4018/java-return-generic3 b/t/t4018/java-return-generic3
new file mode 100644
index 0000000000..3db1a1ddba
--- /dev/null
+++ b/t/t4018/java-return-generic3
@@ -0,0 +1,10 @@
+class MyExample {
+    public void firstMethod() {
+        // Whatever...
+    }
+
+    public <AType, B> Map<AType, B> secondMethod(String[] RIGHT) {
+        // Whatever...
+        return new java.util.HashMap<>(); // ChangeMe
+    }
+}
diff --git a/t/t4018/java-return-generic4 b/t/t4018/java-return-generic4
new file mode 100644
index 0000000000..1fc18a8482
--- /dev/null
+++ b/t/t4018/java-return-generic4
@@ -0,0 +1,10 @@
+class MyExample {
+    public void firstMethod() {
+        // Whatever...
+    }
+
+ public <AType, B> Map<AType, Map<B, B[]>> secondMethod(String[] RIGHT) {
+        // Whatever...
+        return new java.util.HashMap<>(); // ChangeMe
+    }
+}
diff --git a/userdiff.c b/userdiff.c
index 3c3bbe38b0..22f17c1d3e 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -142,7 +142,15 @@ PATTERNS("html",
 	 "[^<>= \t]+"),
 PATTERNS("java",
 	 "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
-	 "^[ \t]*(([A-Za-z_][A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
+         /* Method signatures contain: */
+         /*   modifiers: public static */
+         "^[ \t]*(([A-Za-z_][A-Za-z]*[ \t]+)*"
+         /*   optionally type parameters: <A, B, C> */
+         "(<[A-Za-z0-9_, \t]+>[ \t]+)?"
+         /*   a return type: Map<A, B[]> */
+         "([A-Za-z_]([A-Za-z_0-9<>,]|\\[[ \t]*\\])*[ \t]+)+"
+         /*   the method name followed by the parameter list: myMethod(...) */
+         "[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
 	 /* -- */
 	 "[a-zA-Z_][a-zA-Z0-9_]*"
 	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
-- 
2.32.0