From e7023612eff5ab8f1be3aaff1b26896962aab139 Mon Sep 17 00:00:00 2001
From: Craig Tiller <craig.tiller@gmail.com>
Date: Thu, 28 May 2015 08:00:14 -0700
Subject: [PATCH] Add a test of cmdline usage strings - and make them saner

---
 include/grpc/support/cmdline.h   |  2 +
 src/core/support/cmdline.c       | 70 +++++++++++++++++++++++---------
 test/core/support/cmdline_test.c | 23 +++++++++++
 3 files changed, 75 insertions(+), 20 deletions(-)

diff --git a/include/grpc/support/cmdline.h b/include/grpc/support/cmdline.h
index c2350a07e8c..e5a266666ee 100644
--- a/include/grpc/support/cmdline.h
+++ b/include/grpc/support/cmdline.h
@@ -87,6 +87,8 @@ void gpr_cmdline_on_extra_arg(
 void gpr_cmdline_parse(gpr_cmdline *cl, int argc, char **argv);
 /* Destroy the parser */
 void gpr_cmdline_destroy(gpr_cmdline *cl);
+/* Get a string describing usage */
+char *gpr_cmdline_usage_string(gpr_cmdline *cl, const char *argv0);
 
 #ifdef __cplusplus
 }
diff --git a/src/core/support/cmdline.c b/src/core/support/cmdline.c
index 72f46c1bd72..530952c4371 100644
--- a/src/core/support/cmdline.c
+++ b/src/core/support/cmdline.c
@@ -131,33 +131,63 @@ void gpr_cmdline_on_extra_arg(
   cl->extra_arg_help = help;
 }
 
-static void print_usage_and_die(gpr_cmdline *cl) {
+/* recursively descend argument list, adding the last element
+   to s first - so that arguments are added in the order they were
+   added to the list by api calls */
+static void add_args_to_usage(gpr_strvec *s, arg *a) {
+  char *tmp;
+
+  if (!a) return;
+  add_args_to_usage(s, a->next);
+
+  switch (a->type) {
+    case ARGTYPE_BOOL:
+      gpr_asprintf(&tmp, " [--%s|--no-%s]", a->name, a->name);
+      gpr_strvec_add(s, tmp);
+      break;
+    case ARGTYPE_STRING:
+      gpr_asprintf(&tmp, " [--%s=string]", a->name);
+      gpr_strvec_add(s, tmp);
+      break;
+    case ARGTYPE_INT:
+      gpr_asprintf(&tmp, " [--%s=int]", a->name);
+      gpr_strvec_add(s, tmp);
+      break;
+  }
+}
+
+char *gpr_cmdline_usage_string(gpr_cmdline *cl, const char *argv0) {
   /* TODO(ctiller): make this prettier */
-  arg *a;
-  const char *name = strrchr(cl->argv0, '/');
+  gpr_strvec s;
+  char *tmp;
+  const char *name = strrchr(argv0, '/');
+
   if (name) {
     name++;
   } else {
-    name = cl->argv0;
-  }
-  fprintf(stderr, "Usage: %s", name);
-  for (a = cl->args; a; a = a->next) {
-    switch (a->type) {
-      case ARGTYPE_BOOL:
-        fprintf(stderr, " [--%s|--no-%s]", a->name, a->name);
-        break;
-      case ARGTYPE_STRING:
-        fprintf(stderr, " [--%s=string]", a->name);
-        break;
-      case ARGTYPE_INT:
-        fprintf(stderr, " [--%s=int]", a->name);
-        break;
-    }
+    name = argv0;
   }
+
+  gpr_strvec_init(&s);
+
+  gpr_asprintf(&tmp, "Usage: %s", name);
+  gpr_strvec_add(&s, tmp);
+  add_args_to_usage(&s, cl->args);
   if (cl->extra_arg) {
-    fprintf(stderr, " [%s...]", cl->extra_arg_name);
+    gpr_asprintf(&tmp, " [%s...]", cl->extra_arg_name);
+    gpr_strvec_add(&s, tmp);
   }
-  fprintf(stderr, "\n");
+  gpr_strvec_add(&s, gpr_strdup("\n"));
+
+  tmp = gpr_strvec_flatten(&s, NULL);
+  gpr_strvec_destroy(&s);
+  return tmp;
+}
+
+static void print_usage_and_die(gpr_cmdline *cl) {
+  char *usage = gpr_cmdline_usage_string(cl, cl->argv0);
+  fprintf(stderr, "%s", usage);
+  gpr_free(usage);
   exit(1);
 }
 
diff --git a/test/core/support/cmdline_test.c b/test/core/support/cmdline_test.c
index a7767ace5e8..26153b192cb 100644
--- a/test/core/support/cmdline_test.c
+++ b/test/core/support/cmdline_test.c
@@ -35,6 +35,7 @@
 
 #include <string.h>
 
+#include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/useful.h>
 #include "test/core/util/test_config.h"
@@ -272,6 +273,27 @@ static void test_many(void) {
   gpr_cmdline_destroy(cl);
 }
 
+static void test_usage(void) {
+  gpr_cmdline *cl;
+  char *usage;
+
+  char *str = NULL;
+  int x = 0;
+  int flag = 2;
+
+  cl = gpr_cmdline_create(NULL);
+  gpr_cmdline_add_string(cl, "str", NULL, &str);
+  gpr_cmdline_add_int(cl, "x", NULL, &x);
+  gpr_cmdline_add_flag(cl, "flag", NULL, &flag);
+
+  usage = gpr_cmdline_usage_string(cl, "test");
+  GPR_ASSERT(0 == strcmp(usage,
+    "Usage: test [--str=string] [--x=int] [--flag|--no-flag]\n"));
+  gpr_free(usage);
+
+  gpr_cmdline_destroy(cl);
+}
+
 int main(int argc, char **argv) {
   grpc_test_init(argc, argv);
   test_simple_int();
@@ -289,5 +311,6 @@ int main(int argc, char **argv) {
   test_flag_val_true();
   test_flag_val_false();
   test_many();
+  test_usage();
   return 0;
 }