* introduced 'let' directive

Author: adamansky

README.md

@@ -5,7 +5,7 @@
 - [meta](#meta-)
 - [option](#option-)
 - [check](#check-)
-- [set](#set-)
+- [set|let](#set--let-)
 - [env](#env-)
 - [${}](#-variable-evaluation)
 - [@{}](#-program-output-evaluation)
@@ -523,12 +523,17 @@ set {
 }
 ```
 
-# set {...}
+# set | let {...}
 
 The `set` rule assigns a value to a variable in the build script.
+The expression value is registered during the `init` build phase and then lazily evaluated
+upon the first access to that variable.
+
+If a variable is used multiple times in a declarative context (for example, inside [macros](#macros))
+the let directive is more appropriate, as it is evaluated every time it is accessed in every build phase.
 
 ```cfg
-set {
+set | let {
    | NAME
    | _
    | parent { NAME }
@@ -538,8 +543,6 @@ set {
 }
 ```
 
-`set` is a lazily evaluated rule - the value of set is only computed if the variable or expression is actually used.
-
 The most common form is `set { NAME [VALUES]... }`
 
 Note that in Autark, all variables are either strings or lists. A list is just a string internally,
@@ -1243,7 +1246,7 @@ Example:
 ```cfg
 macro {
   M_ECHO
-  set {
+  let {
     JOIN
     ^{&{1} ' ' &{2}}
   }

autark_core.c

@@ -52,17 +52,23 @@ void unit_env_set_val(struct unit *u, const char *key, const char *val) {
   map_put_str(u->env, key, item);
 }
 
-void unit_env_set_node(struct unit *u, const char *key, struct node *n) {
+void unit_env_set_node(struct unit *u, const char *key, struct node *n, unsigned tag) {
   struct unit_env_item *item = xmalloc(sizeof(*item));
   item->val = 0;
   item->n = n;
+  item->tag = tag;
   map_put_str(u->env, key, item);
 }
 
-struct node* unit_env_get_node(struct unit *u, const char *key) {
+struct node* unit_env_get_node(struct unit *u, const char *key, unsigned *out_tag) {
   struct unit_env_item *item = map_get(u->env, key);
   if (item) {
+    if (out_tag) {
+      *out_tag = item->tag;
+    }
     return item->n;
+  } else if (out_tag)  {
+    *out_tag = 0;
   }
   return 0;
 }

dist/autark.c

@@ -2,7 +2,7 @@
 #define CONFIG_H
 
 #define META_VERSION "0.9.0"
-#define META_REVISION "e6bb7fe"
+#define META_REVISION "947a8ae"
 
 #define MACRO_MAX_RECURSIVE_CALLS 128
 
@@ -755,6 +755,10 @@ char* path_basename(char *path);
 #include <stdbool.h>
 #endif
 
+#define TAG_INIT  1
+#define TAG_SETUP 2
+#define TAG_BUILD 3
+
 #define AUTARK_CACHE  "autark-cache"
 #define AUTARK_SCRIPT "Autark"
 
@@ -771,6 +775,7 @@ char* path_basename(char *path);
 struct unit_env_item {
   const char  *val;
   struct node *n;
+  unsigned     tag;
 };
 
 /// Current execution unit.
@@ -811,7 +816,7 @@ struct env {
     const char *prefix_dir;  // Absolute path to install prefix dir.
     const char *bin_dir;     // Path to the bin dir relative to prefix.
     const char *lib_dir;     // Path to lib dir relative to prefix.
-    const char *data_dir; // Path to lib data dir relative to prefix.
+    const char *data_dir;    // Path to lib data dir relative to prefix.
     const char *include_dir; // Path to include headers dir relative to prefix.
     const char *pkgconf_dir; // Path to pkgconfig dir.
     const char *man_dir;     // Path to man pages dir.
@@ -856,9 +861,9 @@ void unit_ch_src_dir(struct unit*, char *prevcwd);
 
 void unit_env_set_val(struct unit*, const char *key, const char *val);
 
-void unit_env_set_node(struct unit*, const char *key, struct node *n);
+void unit_env_set_node(struct unit*, const char *key, struct node *n, unsigned tag);
 
-struct node* unit_env_get_node(struct unit *u, const char *key);
+struct node* unit_env_get_node(struct unit *u, const char *key, unsigned *out_tag);
 
 const char* unit_env_get(struct node *n, const char *key);
 
@@ -1100,7 +1105,7 @@ const char* node_env_get(struct node*, const char *key);
 
 void node_env_set(struct node*, const char *key, const char *val);
 
-void node_env_set_node(struct node*, const char *key);
+void node_env_set_node(struct node*, const char *key, unsigned tag);
 
 struct node* node_by_product(struct node*, const char *prod, char pathbuf[PATH_MAX]);
 
@@ -3834,6 +3839,17 @@ int node_check_setup(struct node *n) {
 
 static const char* _set_value_get(struct node *n);
 
+static void _set_dispose(struct node *n) {
+  if ((uintptr_t) n->impl != (uintptr_t) -1) {
+    free(n->impl);
+  }
+  n->impl = 0;
+}
+
+static bool _set_is_let(struct node *n) {
+  return strcmp(n->value, "let") == 0;
+}
+
 static struct unit* _unit_for_set(struct node *n, struct node *nn, const char **keyp) {
   if (nn->type == NODE_TYPE_BAG) {
     if (strcmp(nn->value, "root") == 0) {
@@ -3849,10 +3865,29 @@ static struct unit* _unit_for_set(struct node *n, struct node *nn, const char **
   return unit_peek();
 }
 
-static void _set_init(struct node *n);
+static void _set_init_impl(struct node *n) {
+  const char *key = 0;
+  struct unit *unit = n->child ? _unit_for_set(n, n->child, &key) : 0;
+  if (!key) {
+    node_warn(n, "No name specified for 'set' directive");
+    return;
+  }
+  unsigned tag = 0;
+  struct node *nn = unit_env_get_node(unit, key, &tag);
+  if (nn && nn != n) {
+    n->recur_next.n = nn;
+  }
+  unit_env_set_node(unit, key, n, 0);
+}
+
+static void _set_init(struct node *n) {
+  _set_init_impl(n);
+}
 
 static void _set_setup(struct node *n) {
-  _set_init(n);
+  if (_set_is_let(n)) {
+    _set_init_impl(n);
+  }
   if (n->child && strcmp(n->value, "env") == 0) {
     const char *v = _set_value_get(n);
     if (v) {
@@ -3868,18 +3903,10 @@ static void _set_setup(struct node *n) {
   }
 }
 
-static void _set_init(struct node *n) {
-  const char *key = 0;
-  struct unit *unit = n->child ? _unit_for_set(n, n->child, &key) : 0;
-  if (!key) {
-    node_warn(n, "No name specified for 'set' directive");
-    return;
-  }
-  struct node *nn = unit_env_get_node(unit, key);
-  if (nn && nn != n) {
-    n->recur_next.n = nn;
+static void _set_build(struct node *n) {
+  if (_set_is_let(n)) {
+    _set_init_impl(n);
   }
-  unit_env_set_node(unit, key, n);
 }
 
 static const char* _set_value_get(struct node *n) {
@@ -3889,7 +3916,7 @@ static const char* _set_value_get(struct node *n) {
   n->recur_next.active = true;
 
   struct node_foreach *fe = node_find_parent_foreach(n);
-  if (fe) {
+  if (fe || _set_is_let(n)) {
     if ((uintptr_t) n->impl != (uintptr_t) -1) {
       free(n->impl);
     }
@@ -3941,24 +3968,13 @@ static const char* _set_value_get(struct node *n) {
   return n->impl;
 }
 
-static void _set_dispose(struct node *n) {
-  if ((uintptr_t) n->impl != (uintptr_t) -1) {
-    free(n->impl);
-  }
-  n->impl = 0;
-}
-
-static void _set_build(struct node *n) {
-  _set_init(n);
-}
-
 int node_set_setup(struct node *n) {
   n->flags |= NODE_FLG_NO_CWD;
   n->init = _set_init;
   n->setup = _set_setup;
+  n->build = _set_build;
   n->value_get = _set_value_get;
   n->dispose = _set_dispose;
-  n->build = _set_build;
   return 0;
 }
 #ifndef _AMALGAMATE_
@@ -6484,7 +6500,7 @@ static void _find_init(struct node *n) {
     node_fatal(AK_ERROR_SCRIPT_SYNTAX, n, "No name specified for '%s' directive", n->value);
     return;
   }
-  unit_env_set_node(unit, key, n);
+  unit_env_set_node(unit, key, n, TAG_INIT);
 }
 
 static void _find_dispose(struct node *n) {
@@ -6551,7 +6567,7 @@ static void _macro_init(struct node *n) {
     return;
   }
   _macro_remove(n);
-  unit_env_set_node(unit, key, n);
+  unit_env_set_node(unit, key, n, TAG_INIT);
 }
 
 static void _macro_dispose(struct node *n) {
@@ -6682,7 +6698,7 @@ static void _call_init(struct node *n) {
     node_warn(n, "No name specified for 'call' directive");
     return;
   }
-  struct node *mn = unit_env_get_node(unit, key);
+  struct node *mn = unit_env_get_node(unit, key, 0);
   if (!mn) {
     node_fatal(0, n, "Unknown script macro: %s", key);
     return;
@@ -6786,17 +6802,23 @@ void unit_env_set_val(struct unit *u, const char *key, const char *val) {
   map_put_str(u->env, key, item);
 }
 
-void unit_env_set_node(struct unit *u, const char *key, struct node *n) {
+void unit_env_set_node(struct unit *u, const char *key, struct node *n, unsigned tag) {
   struct unit_env_item *item = xmalloc(sizeof(*item));
   item->val = 0;
   item->n = n;
+  item->tag = tag;
   map_put_str(u->env, key, item);
 }
 
-struct node* unit_env_get_node(struct unit *u, const char *key) {
+struct node* unit_env_get_node(struct unit *u, const char *key, unsigned *out_tag) {
   struct unit_env_item *item = map_get(u->env, key);
   if (item) {
+    if (out_tag) {
+      *out_tag = item->tag;
+    }
     return item->n;
+  } else if (out_tag)  {
+    *out_tag = 0;
   }
   return 0;
 }
@@ -8385,7 +8407,7 @@ static unsigned _rule_type(const char *key, unsigned *flags) {
     return NODE_TYPE_SUBST;
   } else if (strcmp(key, "^") == 0) {
     return NODE_TYPE_JOIN;
-  } else if (strcmp(key, "set") == 0 || strcmp(key, "env") == 0) {
+  } else if (strcmp(key, "set") == 0 || strcmp(key, "env") == 0 || strcmp(key, "let") == 0) {
     return NODE_TYPE_SET;
   } else if (strcmp(key, "check") == 0) {
     return NODE_TYPE_CHECK;
@@ -9199,14 +9221,14 @@ void node_env_set(struct node *n, const char *key, const char *val) {
   }
 }
 
-void node_env_set_node(struct node *n_, const char *key) {
+void node_env_set_node(struct node *n_, const char *key, unsigned tag) {
   if (key[0] == '_' && key[1] == '\0') {
     // Skip on special '_' key
     return;
   }
   for (struct node *n = n_; n; n = n->parent) {
     if (n->unit) {
-      unit_env_set_node(n->unit, key, n_);
+      unit_env_set_node(n->unit, key, n_, tag);
       return;
     }
   }