From b3bf03d695ddad389bb3a569e93eca598c8c41ad Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Tue, 13 Dec 2016 08:21:24 -0800
Subject: [PATCH] Change Kernel#warn to call Warning.warn

This allows Warning.warn to filter/process warning messages
generated by Kernel#warn.  Currently, Warning.warn can only handle
messages generated by the rb_warn/rb_warning C functions.

The Kernel#warn API is different than the Warning.warn API, this
tries to get similar behavior, but there may be corner cases
where the behavior is different.

This makes str_end_with_asciichar in io.c no longer static so it
can be called from error.c.
---
 error.c | 41 ++++++++++++++++++++++++++++++++---------
 io.c    |  2 +-
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/error.c b/error.c
index e03a4ee..772364d 100644
--- a/error.c
+++ b/error.c
@@ -38,13 +38,14 @@
 
 VALUE rb_iseqw_local_variables(VALUE iseqval);
 VALUE rb_iseqw_new(const rb_iseq_t *);
+int str_end_with_asciichar(VALUE str, int c);
 
 VALUE rb_eEAGAIN;
 VALUE rb_eEWOULDBLOCK;
 VALUE rb_eEINPROGRESS;
 VALUE rb_mWarning;
 
-static ID id_warn;
+static ID id_warn, id_flatten_b;
 
 extern const char ruby_description[];
 
@@ -276,23 +277,44 @@ rb_enc_warning(rb_encoding *enc, const char *fmt, ...)
  * call-seq:
  *    warn(msg, ...)   -> nil
  *
- * Displays each of the given messages followed by a record separator on
- * STDERR unless warnings have been disabled (for example with the
- * <code>-W0</code> flag).
- *
+ * If warnings have been disabled (for example with the
+ * <code>-W0</code> flag), does nothing.  Otherwise, 
+ * flattens the array of arguments and converts the
+ * entries to strings, makes sure all strings end with
+ * a newline, joins all strings into a single string,
+ * and calls <code>Warning.warn</code> with the 
+ * resulting string.
+ * 
  *    warn("warning 1", "warning 2")
+ *    warn(["warning 1\n", "warning 2"])
+ *    warn("warning 1", "warning 2\n")
  *
- *  <em>produces:</em>
+ *  <em>all call <code>Warning.warn</code> with:</em>
  *
- *    warning 1
- *    warning 2
+ *    "warning 1\nwarning 2\n"
  */
 
 static VALUE
 rb_warn_m(int argc, VALUE *argv, VALUE exc)
 {
     if (!NIL_P(ruby_verbose) && argc > 0) {
-	rb_io_puts(argc, argv, rb_stderr);
+	int i;
+	VALUE str;
+	VALUE ary = rb_ary_new_from_values(argc, argv);
+	rb_funcall(ary, id_flatten_b, 0);
+	Check_Type(ary, T_ARRAY);
+	argc = RARRAY_LEN(ary);
+	argv = RARRAY_PTR(ary);
+
+	for(i = 0; i < argc; i++) {
+	    str = rb_obj_as_string(argv[i]);
+	    if (RSTRING_LEN(str) == 0 || !str_end_with_asciichar(str, '\n')) {
+		str = rb_str_cat(rb_str_dup(str), "\n", 1);
+	    }
+	    rb_ary_store(ary, i, str);
+	}
+
+	rb_write_warning_str(rb_ary_join(ary, rb_str_new("", 0)));
     }
     return Qnil;
 }
@@ -2108,6 +2130,7 @@ Init_Exception(void)
     id_errno = rb_intern_const("errno");
     id_i_path = rb_intern_const("@path");
     id_warn = rb_intern_const("warn");
+    id_flatten_b = rb_intern_const("flatten!");
     id_iseq = rb_make_internal_id();
 }
 
diff --git a/io.c b/io.c
index 1f00f6c..865b3a6 100644
--- a/io.c
+++ b/io.c
@@ -7123,7 +7123,7 @@ rb_f_putc(VALUE recv, VALUE ch)
 }
 
 
-static int
+int
 str_end_with_asciichar(VALUE str, int c)
 {
     long len = RSTRING_LEN(str);
-- 
2.10.1