From 11473c515c4cd69d5925ff65244ce7250699c03f Mon Sep 17 00:00:00 2001
From: Christian Hergert <chergert@redhat.com>
Date: Wed, 24 Dec 2025 10:28:36 -0800
Subject: [PATCH] app: be selective about when to map font-dirs.xml

If the command calling `flatpak build` has already specified a
font-dirs.xml to map, then mapping in again may break (as exemplified in
Builder and Foundry).

This checks to see if an argument has already been mapped in before doing
so and resolves the issue with Builder/Foundry.

Follow-up to !6138

Fixes: GNOME/gnome-builder#2387

(cherry picked from commit c896faae19c56b97324c9aec10d647cfcfe01fd4)
---
 app/flatpak-builtins-build.c | 46 +++++++++++++++++++++++++++++++++---
 1 file changed, 43 insertions(+), 3 deletions(-)

diff --git a/app/flatpak-builtins-build.c b/app/flatpak-builtins-build.c
index 7989ea12..3596c24d 100644
--- a/app/flatpak-builtins-build.c
+++ b/app/flatpak-builtins-build.c
@@ -59,14 +59,53 @@ static GOptionEntry options[] = {
   { NULL }
 };
 
+static gboolean
+has_bind_mount_for_path (FlatpakBwrap *bwrap, const char *dest_path)
+{
+  guint i;
+
+  for (i = 0; i < bwrap->argv->len; i++)
+    {
+      const char *arg = g_ptr_array_index (bwrap->argv, i);
+
+      if (g_strcmp0 (arg, "--bind") == 0 ||
+          g_strcmp0 (arg, "--bind-try") == 0 ||
+          g_strcmp0 (arg, "--ro-bind") == 0 ||
+          g_strcmp0 (arg, "--ro-bind-try") == 0 ||
+          g_strcmp0 (arg, "--bind-data") == 0 ||
+          g_strcmp0 (arg, "--ro-bind-data") == 0)
+        {
+          /* For all bind mount types, the destination path is at index i+2.
+           *
+           *   --bind/--ro-bind/--bind-try/--ro-bind-try: type, src, dest
+           *   --bind-data/--ro-bind-data: type, fd_string, dest
+           */
+          if (i + 2 < bwrap->argv->len)
+            {
+              const char *dest = g_ptr_array_index (bwrap->argv, i + 2);
+              if (dest != NULL && g_strcmp0 (dest, dest_path) == 0)
+                return TRUE;
+            }
+        }
+    }
+
+  return FALSE;
+}
+
 static void
 add_empty_font_dirs_xml (FlatpakBwrap *bwrap)
 {
+  const char *font_dirs_path = "/run/host/font-dirs.xml";
+
+  /* Check if a bind mount already exists for this path */
+  if (has_bind_mount_for_path (bwrap, font_dirs_path))
+    return;
+
   g_autoptr(GString) xml_snippet = g_string_new ("<?xml version=\"1.0\"?>\n"
                                                  "<!DOCTYPE fontconfig SYSTEM \"urn:fontconfig:fonts.dtd\">\n"
                                                  "<fontconfig></fontconfig>\n");
 
-  if (!flatpak_bwrap_add_args_data (bwrap, "font-dirs.xml", xml_snippet->str, xml_snippet->len, "/run/host/font-dirs.xml", NULL))
+  if (!flatpak_bwrap_add_args_data (bwrap, "font-dirs.xml", xml_snippet->str, xml_snippet->len, font_dirs_path, NULL))
     g_warning ("Unable to add fontconfig data snippet");
 }
 
@@ -570,8 +609,6 @@ flatpak_builtin_build (int argc, char **argv, GCancellable *cancellable, GError
                                          instance_id, NULL, cancellable, error))
     return FALSE;
 
-  add_empty_font_dirs_xml (bwrap);
-
   for (i = 0; opt_bind_mounts != NULL && opt_bind_mounts[i] != NULL; i++)
     {
       char *split = strchr (opt_bind_mounts[i], '=');
@@ -588,6 +625,9 @@ flatpak_builtin_build (int argc, char **argv, GCancellable *cancellable, GError
                               NULL);
     }
 
+  /* Add empty font-dirs.xml only if user hasn't already mapped it */
+  add_empty_font_dirs_xml (bwrap);
+
   if (opt_build_dir != NULL)
     {
       flatpak_bwrap_add_args (bwrap,