From 18394bc05dc4cadb2dc193cfeb78598c70447869 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Wed, 19 Oct 2022 10:26:22 +0200
Subject: Add support for post hoc prerequisites

Unlike normal and ad hoc prerequisites, a post hoc prerequisite is built
after the target, not before. It may also form a dependency cycle together
with normal/ad hoc prerequisites. In other words, all this form of dependency
guarantees is that a post hoc prerequisite will be built if its dependent
target is built.

See the NEWS file for details and an example.
---
 libbuild2/dist/operation.cxx | 30 ++++++++++++++++--------------
 libbuild2/dist/rule.cxx      |  4 ++++
 2 files changed, 20 insertions(+), 14 deletions(-)

(limited to 'libbuild2/dist')

diff --git a/libbuild2/dist/operation.cxx b/libbuild2/dist/operation.cxx
index 91d2321..9a662df 100644
--- a/libbuild2/dist/operation.cxx
+++ b/libbuild2/dist/operation.cxx
@@ -85,7 +85,7 @@ namespace build2
       if (auto* m = rs.find_module<module> (module::name))
         m->distributed = true;
 
-      load (vs, rs, bf, out_base, src_base, l);
+      perform_load (vs, rs, bf, out_base, src_base, l);
     }
 
     // Enter the specified source file as a target of type T. The path is
@@ -301,17 +301,17 @@ namespace build2
                   const operation_info* poif (ops[pid]);
                   ctx.current_operation (*poif, oif, false /* diag_noise */);
                   action a (dist_id, poif->id, oif->id);
-                  match (params, a, ts,
-                         1     /* diag (failures only) */,
-                         false /* progress */);
+                  perform_match (params, a, ts,
+                                 1     /* diag (failures only) */,
+                                 false /* progress */);
                 }
               }
 
               ctx.current_operation (*oif, nullptr, false /* diag_noise */);
               action a (dist_id, oif->id);
-              match (params, a, ts,
-                     1     /* diag (failures only) */,
-                     false /* progress */);
+              perform_match (params, a, ts,
+                             1     /* diag (failures only) */,
+                             false /* progress */);
 
               if (auto po = oif->post_operation)
               {
@@ -320,9 +320,9 @@ namespace build2
                   const operation_info* poif (ops[pid]);
                   ctx.current_operation (*poif, oif, false /* diag_noise */);
                   action a (dist_id, poif->id, oif->id);
-                  match (params, a, ts,
-                         1     /* diag (failures only) */,
-                         false /* progress */);
+                  perform_match (params, a, ts,
+                                 1     /* diag (failures only) */,
+                                 false /* progress */);
                 }
               }
             }
@@ -1092,6 +1092,8 @@ namespace build2
       // given the prescribed semantics of adhoc (match/execute but otherwise
       // ignore) is followed.
       //
+      // Note that we don't need to do anything for posthoc.
+      //
       if (i == include_type::excluded)
       {
         l5 ([&]{trace << "overriding exclusion of " << p;});
@@ -1116,11 +1118,11 @@ namespace build2
       nullptr, // meta-operation pre
       &dist_operation_pre,
       &dist_load_load,
-      &search, // normal search
-      nullptr, // no match (see dist_execute()).
+      &perform_search,    // normal search
+      nullptr,            // no match (see dist_execute()).
       &dist_load_execute,
-      nullptr, // operation post
-      nullptr, // meta-operation post
+      nullptr,            // operation post
+      nullptr,            // meta-operation post
       &dist_include
     };
 
diff --git a/libbuild2/dist/rule.cxx b/libbuild2/dist/rule.cxx
index ac3d440..e47f1f8 100644
--- a/libbuild2/dist/rule.cxx
+++ b/libbuild2/dist/rule.cxx
@@ -79,6 +79,10 @@ namespace build2
                   !p.dir.sub (out_root))
                 continue;
 
+              // @@ TODO: this can actually be order-dependent: for example
+              //    libs{} prerequisite may be unknown because we haven't
+              //    matched the lib{} group yet.
+              //
               fail << "prerequisite " << k << " is not existing source file "
                    << "nor known output target" << endf;
             }
-- 
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