load-fragment: Expand specifiers in conditions.

Add specifier expansion to Path and String conditions.

Specifier expansion for conditions will help create instance
and user session units by allowing us to template conditions
based on the instance or user session parameters.

An example would be a system-wide user session service file
that conditionally runs based on whether a user has the
service configured through a configuration file in ~/.config/.

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index c6422619f5d008db5dcd104c1347a88340d635f1..482d28b79587221dc2523532663350100f0b75be 100644 (file)
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -1469,6 +1469,7 @@ int config_parse_unit_condition_path(
         Unit *u = data;
         bool trigger, negate;
         Condition *c;
+        char *p;
 
         assert(filename);
         assert(lvalue);
@@ -1483,14 +1484,19 @@ int config_parse_unit_condition_path(
         if (negate)
                 rvalue++;
 
-        if (!path_is_absolute(rvalue)) {
-                log_error("[%s:%u] Path in condition not absolute, ignoring: %s", filename, line, rvalue);
+        p = unit_full_printf(u, rvalue);
+        if (!p)
+                return -ENOMEM;
+
+        if (!path_is_absolute(p)) {
+                log_error("[%s:%u] Path in condition not absolute, ignoring: %s", filename, line, p);
                 return 0;
         }
 
-        c = condition_new(cond, rvalue, trigger, negate);
+        c = condition_new(cond, p, trigger, negate);
         if (!c)
                 return -ENOMEM;
+        free(p);
 
         LIST_PREPEND(Condition, conditions, u->conditions, c);
         return 0;
@@ -1510,6 +1516,7 @@ int config_parse_unit_condition_string(
         Unit *u = data;
         bool trigger, negate;
         Condition *c;
+        char *s;
 
         assert(filename);
         assert(lvalue);
@@ -1524,9 +1531,14 @@ int config_parse_unit_condition_string(
         if (negate)
                 rvalue++;
 
-        c = condition_new(cond, rvalue, trigger, negate);
+        s = unit_full_printf(u, rvalue);
+        if (!s)
+                return -ENOMEM;
+
+        c = condition_new(cond, s, trigger, negate);
         if (!c)
                 return log_oom();
+        free(s);
 
         LIST_PREPEND(Condition, conditions, u->conditions, c);
         return 0;