From f91468192ad7066a5e6fa63ddc4e4231e632a457 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Wed, 18 Nov 2020 12:51:49 +0300
Subject: Remove target files on ad hoc rule update buildscript error

---
 libbuild2/adhoc-rule-buildscript.cxx | 19 +++++++++-
 tests/recipe/buildscript/testscript  | 73 +++++++++++++++++++++++++++++-------
 2 files changed, 78 insertions(+), 14 deletions(-)

diff --git a/libbuild2/adhoc-rule-buildscript.cxx b/libbuild2/adhoc-rule-buildscript.cxx
index a09d2c7..9470d3c 100644
--- a/libbuild2/adhoc-rule-buildscript.cxx
+++ b/libbuild2/adhoc-rule-buildscript.cxx
@@ -10,7 +10,7 @@
 #include <libbuild2/target.hxx>
 #include <libbuild2/context.hxx>
 #include <libbuild2/algorithm.hxx>
-#include <libbuild2/filesystem.hxx>  // path_perms()
+#include <libbuild2/filesystem.hxx>  // path_perms(), auto_rmfile
 #include <libbuild2/diagnostics.hxx>
 
 #include <libbuild2/parser.hxx> // attributes
@@ -563,6 +563,20 @@ namespace build2
 
       if (!ctx.dry_run || verb >= 2)
       {
+        // On failure remove the target files that may potentially exist but
+        // be invalid.
+        //
+        small_vector<auto_rmfile, 8> rms;
+
+        if (!ctx.dry_run)
+        {
+          for (const target* m (&t); m != nullptr; m = m->adhoc_member)
+          {
+            if (auto* f = m->is_a<file> ())
+              rms.emplace_back (f->path ());
+          }
+        }
+
         build::script::default_runner r;
         p.execute (*rs, *bs, e, script, r);
 
@@ -588,6 +602,9 @@ namespace build2
           }
 #endif
           dd.check_mtime (tp);
+
+          for (auto& rm: rms)
+            rm.cancel ();
         }
       }
     }
diff --git a/tests/recipe/buildscript/testscript b/tests/recipe/buildscript/testscript
index 787bafd..6b3f6c7 100644
--- a/tests/recipe/buildscript/testscript
+++ b/tests/recipe/buildscript/testscript
@@ -17,24 +17,71 @@
 : update
 :
 {
-  echo 'bar' >=bar;
+  : success
+  :
+  {
+    echo 'bar' >=bar;
 
-  cat <<EOI >=buildfile;
-    foo: bar
-    {{
-      cp $path($<) $path($>)
-    }}
-    EOI
+    cat <<EOI >=buildfile;
+      foo: bar
+      {{
+        cp $path($<) $path($>)
+      }}
+      EOI
 
-  $* 2>'cp file{foo}';
+    $* 2>'cp file{foo}';
 
-  cat <<<foo >'bar';
+    cat <<<foo >'bar';
 
-  # While at it, make sure there is no rebuild.
-  #
-  $* 2>/'info: dir{./} is up to date';
+    # While at it, make sure there is no rebuild.
+    #
+    $* 2>/'info: dir{./} is up to date';
 
-  $* clean 2>-
+    $* clean 2>-
+  }
+
+  : error
+  :
+  : Test that the target file is removed on error and is created on subsequent
+  : successful update.
+  :
+  {
+    echo 'bar' >=bar;
+
+    cat <<EOI >=buildfile;
+      foo: bar
+      {{
+        diag concat $<
+
+        t = $path($>)
+        p = $path($<)
+
+        cp $p $t
+
+        cat $(p).baz >>$t
+      }}
+      EOI
+
+    $* 2>>~%EOE% != 0;
+      concat file{bar.}
+      %cat: unable to print '.+bar.baz': .+%
+      buildfile:10:3: error: cat exited with code 1
+      %.+
+      EOE
+
+    test -f foo != 0;
+
+    echo 'baz' >=bar.baz;
+
+    $* 2>'concat file{bar.}';
+
+    cat <<<foo >>EOO;
+      bar
+      baz
+      EOO
+
+    $* clean 2>-
+  }
 }
 
 : clean
-- 
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