Fix dist bug where missing source file would be silently ignored

2 files changed, 43 insertions, 12 deletions

diff --git a/build2/dist/operation.cxx b/build2/dist/operation.cxx
index f42217e..6692156 100644
--- a/build2/dist/operation.cxx
+++ b/build2/dist/operation.cxx
@@ -79,8 +79,8 @@ namespace build2
         fail << "in-tree distribution of target " << t <<
           info << "distribution requires out-of-tree build";
 
-      // Make sure we have the necessary configuration before
-      // we get down to business.
+      // Make sure we have the necessary configuration before we get down to
+      // business.
       //
       auto l (rs->vars["dist.root"]);
 
@@ -155,10 +155,9 @@ namespace build2
         }
       }
 
-      // Add buildfiles that are not normally loaded as part of the
-      // project, for example, the export stub. They will still be
-      // ignored on the next step if the user explicitly marked them
-      // nodist.
+      // Add buildfiles that are not normally loaded as part of the project,
+      // for example, the export stub. They will still be ignored on the next
+      // step if the user explicitly marked them dist=false.
       //
       auto add_adhoc = [&trace] (const scope& rs, const path& f)
       {
@@ -204,9 +203,8 @@ namespace build2
         }
       }
 
-      // Collect the files. We want to take the snapshot of targets
-      // since updating some of them may result in more targets being
-      // entered.
+      // Collect the files. We want to take the snapshot of targets since
+      // updating some of them may result in more targets being entered.
       //
       action_targets files;
       const variable& dist_var (var_pool["dist"]);
diff --git a/build2/dist/rule.cxx b/build2/dist/rule.cxx
index ab00d41..b288a66 100644
--- a/build2/dist/rule.cxx
+++ b/build2/dist/rule.cxx
@@ -36,12 +36,45 @@ namespace build2
         if (p.proj ())
           continue;
 
-        const target& pt (p.search (t));
+        // We used to always search and match but that resulted in the
+        // undesirable behavior in case one of the "source" files is
+        // missing. In this case we would enter a target as "output", this
+        // rule would match it, and then dist_execute() would ignore it by
+        // default.
+        //
+        // So now if this is a file target (we still want to always "see
+        // through" other targets like aliases), we will only match it if (1)
+        // it exists in src or (2) it exists as a target. It feels like we
+        // don't need the stronger "... and not implied" condition since if it
+        // is mentioned as a target, then it is in out (we don't do the same
+        // target in both src/out).
+        //
+        const target* pt (nullptr);
+        if (p.is_a<file> ())
+        {
+          pt = p.load ();
+
+          if (pt == nullptr)
+          {
+            // Search for an existing target or existing file in src.
+            //
+            const prerequisite_key& k (p.key ());
+            pt = k.tk.type->search (t, k);
+
+            if (pt == nullptr)
+              fail << "prerequisite " << k << " is not existing source file "
+                   << "nor known output target" << endf;
+
+            search_custom (p.prerequisite, *pt); // Cache.
+          }
+        }
+        else
+          pt = &p.search (t);
 
         // Don't match targets that are outside of our project.
         //
-        if (pt.dir.sub (out_root))
-          build2::match (a, pt);
+        if (pt->dir.sub (out_root))
+          build2::match (a, *pt);
       }
 
       return noop_recipe; // We will never be executed.