Enforce exclusive output options

Currently, any output option (e.g., --version or --libs) will be set as
valid and what's output is at the mercy of the order of the output
handling code in main(). However, most combinations of output would make
no sense to be used together. For example, mixing --modversion and
--print-provides provides no way to differentiate between the output
from the options. Further, mixing --variable and --cflags currently
causes an error because there's no space separating the option outputs.

Instead, keep track of when an output option has been set and ignore
subsequent output options. There are currently two exceptions:

1. Any combination of --cflags* and --libs* are allowed.

2. Both --print-requires and --print-requires-private can be used
   together as the user may just not care which is private.

Freedesktop #54391 (https://bugs.freedesktop.org/show_bug.cgi?id=54391)

2 files changed, 46 insertions, 0 deletions

diff --git a/check/check-print-options b/check/check-print-options
index f9ce636..17aec1d 100755
--- a/check/check-print-options
+++ b/check/check-print-options
@@ -37,3 +37,18 @@ run_test --print-requires-private requires-test
 RESULT="sub1 Subdirectory package 1 - Test package 1 for subdirectory
 sub2 Subdirectory package 2 - Test package 2 for subdirectory"
 PKG_CONFIG_LIBDIR="$srcdir/sub" run_test --list-all
+
+# Check handling when multiple incompatible options are set
+RESULT="Ignoring incompatible output option \"--modversion\"
+$PACKAGE_VERSION"
+run_test --version --modversion simple
+
+RESULT="Ignoring incompatible output option \"--version\"
+1.0.0"
+run_test --modversion --version simple
+
+# --print-requires/--print-requires-private allowed together
+RESULT="public-dep >= 1
+private-dep >= 1"
+run_test --print-requires --print-requires-private requires-test
+run_test --print-requires-private --print-requires requires-test
diff --git a/main.c b/main.c
index deb32f0..3c13f8e 100644
--- a/main.c
+++ b/main.c
@@ -59,6 +59,7 @@ static gboolean want_variable_list = FALSE;
 static gboolean want_debug_spew = FALSE;
 static gboolean want_verbose_errors = FALSE;
 static gboolean want_stdout_errors = FALSE;
+static gboolean output_opt_set = FALSE;
 
 void
 debug_spew (const char *format, ...)
@@ -155,6 +156,35 @@ static gboolean
 output_opt_cb (const char *opt, const char *arg, gpointer data,
                GError **error)
 {
+  /* only allow one output mode, with a few exceptions */
+  if (output_opt_set)
+    {
+      gboolean bad_opt = TRUE;
+
+      /* multiple flag options (--cflags --libs-only-l) allowed */
+      if (pkg_flags != 0 &&
+          (strcmp (opt, "--libs") == 0 ||
+           strcmp (opt, "--libs-only-l") == 0 ||
+           strcmp (opt, "--libs-only-other") == 0 ||
+           strcmp (opt, "--libs-only-L") == 0 ||
+           strcmp (opt, "--cflags") == 0 ||
+           strcmp (opt, "--cflags-only-I") == 0 ||
+           strcmp (opt, "--cflags-only-other") == 0))
+        bad_opt = FALSE;
+
+      /* --print-requires and --print-requires-private allowed */
+      if ((want_requires && strcmp (opt, "--print-requires-private") == 0) ||
+          (want_requires_private && strcmp (opt, "--print-requires") == 0))
+        bad_opt = FALSE;
+
+      if (bad_opt)
+        {
+          fprintf (stderr, "Ignoring incompatible output option \"%s\"\n",
+                   opt);
+          return TRUE;
+        }
+    }
+
   if (strcmp (opt, "--version") == 0)
     want_my_version = TRUE;
   else if (strcmp (opt, "--modversion") == 0)
@@ -192,6 +222,7 @@ output_opt_cb (const char *opt, const char *arg, gpointer data,
   else
     return FALSE;
 
+  output_opt_set = TRUE;
   return TRUE;
 }