path-lookup: Allow setting generator paths via environment

This adds SYSTEMD_GENERATOR_PATH and SYSTEMD_ENVIRONMENT_GENERATOR_PATH
environment variables that will be read in the same manner as
SYSTEMD_UNIT_PATH is. i.e. if set, these paths will be used and a
trailing empty entry means that the usual paths will be appended, while
no trailing entry means that solely the given paths are used.

diff --git a/src/shared/path-lookup.c b/src/shared/path-lookup.c
index 0dd6c831ed22ad1783b79b5f9d03ff83b626f97b..20d6c03a9ad40a4bec31f7a99501dc845d04a519 100644 (file)
--- a/src/shared/path-lookup.c
+++ b/src/shared/path-lookup.c
@@ -833,37 +833,90 @@ void lookup_paths_flush_generator(LookupPaths *p) {
 }
 
 char **generator_binary_paths(UnitFileScope scope) {
+        bool append = false; /* Add items from SYSTEMD_GENERATOR_PATH before normal directories */
+        _cleanup_strv_free_ char **paths = NULL;
+        int r;
 
-        switch (scope) {
+        /* First priority is whatever has been passed to us via env vars */
+        r = get_paths_from_environ("SYSTEMD_GENERATOR_PATH", &paths, &append);
+        if (r < 0)
+                return NULL;
 
-        case UNIT_FILE_SYSTEM:
-                return strv_new("/run/systemd/system-generators",
-                                "/etc/systemd/system-generators",
-                                "/usr/local/lib/systemd/system-generators",
-                                SYSTEM_GENERATOR_PATH);
+        if (!paths || append) {
+                _cleanup_strv_free_ char **add = NULL;
 
-        case UNIT_FILE_GLOBAL:
-        case UNIT_FILE_USER:
-                return strv_new("/run/systemd/user-generators",
-                                "/etc/systemd/user-generators",
-                                "/usr/local/lib/systemd/user-generators",
-                                USER_GENERATOR_PATH);
+                switch (scope) {
 
-        default:
-                assert_not_reached("Hmm, unexpected scope.");
+                case UNIT_FILE_SYSTEM:
+                        add = strv_new("/run/systemd/system-generators",
+                                       "/etc/systemd/system-generators",
+                                       "/usr/local/lib/systemd/system-generators",
+                                       SYSTEM_GENERATOR_PATH);
+                        break;
+
+                case UNIT_FILE_GLOBAL:
+                case UNIT_FILE_USER:
+                        add = strv_new("/run/systemd/user-generators",
+                                       "/etc/systemd/user-generators",
+                                       "/usr/local/lib/systemd/user-generators",
+                                       USER_GENERATOR_PATH);
+                        break;
+
+                default:
+                        assert_not_reached("Hmm, unexpected scope.");
+                }
+
+                if (!add)
+                        return NULL;
+
+                if (paths) {
+                        r = strv_extend_strv(&paths, add, true);
+                        if (r < 0)
+                                return NULL;
+                } else
+                        /* Small optimization: if paths is NULL (and it usually is), we can simply assign 'add' to it,
+                         * and don't have to copy anything */
+                        paths = TAKE_PTR(add);
         }
+
+        return TAKE_PTR(paths);
 }
 
 char **env_generator_binary_paths(bool is_system) {
+        bool append = false; /* Add items from SYSTEMD_ENVIRONMENT_GENERATOR_PATH before normal directories */
+        _cleanup_strv_free_ char **paths = NULL;
+        _cleanup_strv_free_ char **add = NULL;
+        int r;
 
-        if (is_system)
-                return strv_new("/run/systemd/system-environment-generators",
-                                "/etc/systemd/system-environment-generators",
-                                "/usr/local/lib/systemd/system-environment-generators",
-                                SYSTEM_ENV_GENERATOR_PATH);
-        else
-                return strv_new("/run/systemd/user-environment-generators",
-                                "/etc/systemd/user-environment-generators",
-                                "/usr/local/lib/systemd/user-environment-generators",
-                                USER_ENV_GENERATOR_PATH);
+        /* First priority is whatever has been passed to us via env vars */
+        r = get_paths_from_environ("SYSTEMD_ENVIRONMENT_GENERATOR_PATH", &paths, &append);
+        if (r < 0)
+                return NULL;
+
+        if (!paths || append) {
+                if (is_system)
+                        add = strv_new("/run/systemd/system-environment-generators",
+                                        "/etc/systemd/system-environment-generators",
+                                        "/usr/local/lib/systemd/system-environment-generators",
+                                        SYSTEM_ENV_GENERATOR_PATH);
+                else
+                        add = strv_new("/run/systemd/user-environment-generators",
+                                       "/etc/systemd/user-environment-generators",
+                                       "/usr/local/lib/systemd/user-environment-generators",
+                                       USER_ENV_GENERATOR_PATH);
+
+                if (!add)
+                        return NULL;
+        }
+
+        if (paths) {
+                r = strv_extend_strv(&paths, add, true);
+                if (r < 0)
+                        return NULL;
+        } else
+                /* Small optimization: if paths is NULL (and it usually is), we can simply assign 'add' to it,
+                 * and don't have to copy anything */
+                paths = TAKE_PTR(add);
+
+        return TAKE_PTR(paths);
 }