[PATCH v2 1/3] userdiff: support Java type parameters

[Andrei Rybak <rybak.a.v@xxxxxxxxx>]

A class or interface in Java [1] can have type parameters immediately
following the name in the declaration, surrounded by angle brackets
(paired less than and greater than signs).[2]  Example of a class with
type parameters "A" and "N":

    public class ParameterizedClass<A, N> {
        private A field1;
        private N field2;
    }

Support matching a parameterized class or interface declaration with
type parameters immediately following the name of the type in the
builtin userdiff pattern for Java.  Do so by just allowing matching the
first character after the name of the type to "<".

An alternative approach could be to match both the opening and the
closing angle brackets and matching the content between them in various
ways.  Just use the simpler regex for now.

[1] Since Java 5 released in 2004.
[2] Detailed description is available in the Java Language
    Specification, sections "Type Variables" and "Parameterized Types":
    https://docs.oracle.com/javase/specs/jls/se17/html/jls-4.html#jls-4.4

Signed-off-by: Andrei Rybak <rybak.a.v@xxxxxxxxx>
---
 t/t4018/java-class-type-parameters             | 6 ++++++
 t/t4018/java-class-type-parameters-implements  | 6 ++++++
 t/t4018/java-interface-type-parameters         | 6 ++++++
 t/t4018/java-interface-type-parameters-extends | 6 ++++++
 userdiff.c                                     | 2 +-
 5 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 t/t4018/java-class-type-parameters
 create mode 100644 t/t4018/java-class-type-parameters-implements
 create mode 100644 t/t4018/java-interface-type-parameters
 create mode 100644 t/t4018/java-interface-type-parameters-extends

diff --git a/t/t4018/java-class-type-parameters b/t/t4018/java-class-type-parameters
new file mode 100644
index 0000000000..579aa7af21
--- /dev/null
+++ b/t/t4018/java-class-type-parameters
@@ -0,0 +1,6 @@
+class RIGHT<A, B> {
+    static int ONE;
+    static int TWO;
+    static int THREE;
+    private A ChangeMe;
+}
diff --git a/t/t4018/java-class-type-parameters-implements b/t/t4018/java-class-type-parameters-implements
new file mode 100644
index 0000000000..b8038b1866
--- /dev/null
+++ b/t/t4018/java-class-type-parameters-implements
@@ -0,0 +1,6 @@
+class RIGHT<A, B> implements List<A> {
+    static int ONE;
+    static int TWO;
+    static int THREE;
+    private A ChangeMe;
+}
diff --git a/t/t4018/java-interface-type-parameters b/t/t4018/java-interface-type-parameters
new file mode 100644
index 0000000000..a4baa1ae68
--- /dev/null
+++ b/t/t4018/java-interface-type-parameters
@@ -0,0 +1,6 @@
+interface RIGHT<A, B> {
+    static int ONE;
+    static int TWO;
+    static int THREE;
+    public B foo(A ChangeMe);
+}
diff --git a/t/t4018/java-interface-type-parameters-extends b/t/t4018/java-interface-type-parameters-extends
new file mode 100644
index 0000000000..31d7fb3244
--- /dev/null
+++ b/t/t4018/java-interface-type-parameters-extends
@@ -0,0 +1,6 @@
+interface RIGHT<A, B> extends Function<A, B> {
+    static int ONE;
+    static int TWO;
+    static int THREE;
+    public B foo(A ChangeMe);
+}
diff --git a/userdiff.c b/userdiff.c
index d71b82feb7..759e22ffff 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -171,7 +171,7 @@ PATTERNS("html",
 PATTERNS("java",
 	 "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
 	 /* Class, enum, and interface declarations */
-	 "^[ \t]*(([a-z]+[ \t]+)*(class|enum|interface)[ \t]+[A-Za-z][A-Za-z0-9_$]*[ \t]+.*)$\n"
+	 "^[ \t]*(([a-z]+[ \t]+)*(class|enum|interface)[ \t]+[A-Za-z][A-Za-z0-9_$]*([ \t]+|<).*)$\n"
 	 /* Method definitions; note that constructor signatures are not */
 	 /* matched because they are indistinguishable from method calls. */
 	 "^[ \t]*(([A-Za-z_<>&][][?&<>.,A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
-- 
2.39.1