Add ability to add extra depdb entries in in::rule

2 files changed, 21 insertions, 6 deletions

diff --git a/libbuild2/in/rule.cxx b/libbuild2/in/rule.cxx
index 4eab287..941f44d 100644
--- a/libbuild2/in/rule.cxx
+++ b/libbuild2/in/rule.cxx
@@ -157,6 +157,10 @@ namespace build2
         l4 ([&]{trace << "substitution mode mismatch forcing update of"
                       << t;});
 
+      // Then additional depdb entries, if any.
+      //
+      perform_update_depdb (a, t, dd);
+
       // Then the .in file.
       //
       if (dd.expect (i.path ()) != nullptr)
@@ -407,6 +411,11 @@ namespace build2
     }
 
     void rule::
+    perform_update_depdb (action, const target&, depdb&) const
+    {
+    }
+
+    void rule::
     process (const location& l,
              action a, const target& t,
              depdb& dd, size_t dd_skip,
diff --git a/libbuild2/in/rule.hxx b/libbuild2/in/rule.hxx
index 162ce78..ff7a2f3 100644
--- a/libbuild2/in/rule.hxx
+++ b/libbuild2/in/rule.hxx
@@ -5,6 +5,7 @@
 #define LIBBUILD2_IN_RULE_HXX
 
 #include <libbuild2/types.hxx>
+#include <libbuild2/forward.hxx> // depdb
 #include <libbuild2/utility.hxx>
 
 #include <libbuild2/rule.hxx>
@@ -18,7 +19,7 @@ namespace build2
     // Preprocess an .in file.
     //
     // Note that a derived rule can use the target data pad to cache data
-    // (e.g., in match()) to be used in substitute/lookup() calls.
+    // (e.g., in match() or apply()) to be used in substitute/lookup() calls.
     //
     // Note also that currently this rule ignores the dry-run mode (see
     // perform_update() for the rationale).
@@ -52,11 +53,6 @@ namespace build2
 
       // Customization hooks and helpers.
       //
-      // Flags can be used by a custom implementation to alter the lookup
-      // semantics, for example, for special substitutions. Note, however,
-      // that one must make sure this semantics cannot change without changes
-      // to the .in file (see the depdb logic for details).
-      //
 
       // Perform prerequisite search.
       //
@@ -65,8 +61,18 @@ namespace build2
               const prerequisite_member&,
               include_type) const;
 
+      // Additional depdb entries.
+      //
+      virtual void
+      perform_update_depdb (action, const target&, depdb&) const;
+
       // Perform variable lookup.
       //
+      // Flags can be used by a custom implementation to alter the lookup
+      // semantics, for example, for special substitutions. Note, however,
+      // that one must make sure this semantics cannot change without changes
+      // to the .in file (see the depdb logic for details).
+      //
       virtual string
       lookup (const location&,
               action, const target&,