flatpak: Don't hardcode flatpak binary path in launchers

The hardcoded flatpak path breaks all installed applications when flatpak is
updated.

fixes: NixOS#43581

pkgs/development/libraries/flatpak/default.nix

@@ -24,6 +24,7 @@ in stdenv.mkDerivation rec {
     })
     # patch taken from gtk_doc
     ./respect-xml-catalog-files-var.patch
+    ./use-flatpak-from-path.patch
   ];
 
   nativeBuildInputs = [

pkgs/development/libraries/flatpak/use-flatpak-from-path.patch

@@ -0,0 +1,48 @@
+--- a/common/flatpak-dir.c
++++ b/common/flatpak-dir.c
+@@ -5467,7 +5467,7 @@ export_desktop_file (const char   *app,
+
+       new_exec = g_string_new ("");
+       g_string_append_printf (new_exec,
+-                              FLATPAK_BINDIR "/flatpak run --branch=%s --arch=%s",
++                              "flatpak run --branch=%s --arch=%s",
+                               escaped_branch,
+                               escaped_arch);
+
+@@ -6644,8 +6644,8 @@ flatpak_dir_deploy (FlatpakDir          *self,
+                                        error))
+         return FALSE;
+
+-      bin_data = g_strdup_printf ("#!/bin/sh\nexec %s/flatpak run --branch=%s --arch=%s %s \"$@\"\n",
+-                                  FLATPAK_BINDIR, escaped_branch, escaped_arch, escaped_app);
++      bin_data = g_strdup_printf ("#!/bin/sh\nexec flatpak run --branch=%s --arch=%s %s \"$@\"\n",
++                                  escaped_branch, escaped_arch, escaped_app);
+       if (!g_file_replace_contents (wrapper, bin_data, strlen (bin_data), NULL, FALSE,
+                                     G_FILE_CREATE_REPLACE_DESTINATION, NULL, cancellable, error))
+         return FALSE;
+diff --git a/tests/test-bundle.sh b/tests/test-bundle.sh
+index 6937b041..01f8add7 100755
+--- a/tests/test-bundle.sh
++++ b/tests/test-bundle.sh
+@@ -59,7 +59,7 @@ assert_has_dir $FL_DIR/app/org.test.Hello/$ARCH/master/active/files
+ assert_has_dir $FL_DIR/app/org.test.Hello/$ARCH/master/active/export
+ assert_has_file $FL_DIR/exports/share/applications/org.test.Hello.desktop
+ # Ensure Exec key is rewritten
+-assert_file_has_content $FL_DIR/exports/share/applications/org.test.Hello.desktop "^Exec=.*/flatpak run --branch=master --arch=$ARCH --command=hello.sh org.test.Hello$"
++assert_file_has_content $FL_DIR/exports/share/applications/org.test.Hello.desktop "^Exec=flatpak run --branch=master --arch=$ARCH --command=hello.sh org.test.Hello$"
+ assert_has_file $FL_DIR/exports/share/icons/hicolor/64x64/apps/org.test.Hello.png
+ assert_has_file $FL_DIR/exports/share/icons/HighContrast/64x64/apps/org.test.Hello.png
+
+diff --git a/tests/test-run.sh b/tests/test-run.sh
+index 9d83d82e..234e4ec6 100755
+--- a/tests/test-run.sh
++++ b/tests/test-run.sh
+@@ -42,7 +42,7 @@ assert_has_dir $FL_DIR/app/org.test.Hello/$ARCH/master/active/files
+ assert_has_dir $FL_DIR/app/org.test.Hello/$ARCH/master/active/export
+ assert_has_file $FL_DIR/exports/share/applications/org.test.Hello.desktop
+ # Ensure Exec key is rewritten
+-assert_file_has_content $FL_DIR/exports/share/applications/org.test.Hello.desktop "^Exec=.*/flatpak run --branch=master --arch=$ARCH --command=hello.sh org.test.Hello$"
++assert_file_has_content $FL_DIR/exports/share/applications/org.test.Hello.desktop "^Exec=flatpak run --branch=master --arch=$ARCH --command=hello.sh org.test.Hello$"
+ assert_has_file $FL_DIR/exports/share/icons/hicolor/64x64/apps/org.test.Hello.png
+ assert_not_has_file $FL_DIR/exports/share/icons/hicolor/64x64/apps/dont-export.png
+ assert_has_file $FL_DIR/exports/share/icons/HighContrast/64x64/apps/org.test.Hello.png