Fix #1762

nix-store --export, nix-store --dump, and nix dump-path would previously
fail silently if writing the data out failed, because
 a) FdSink::write ignored exceptions, and
 b) the commands relied on FdSink's destructor, which ignores
    exceptions, to flush the data out.

This could cause rather opaque issues with installing nixos, because
nix-store --export would happily proceed even if it couldn't write its
data out (e.g. if nix-store --import on the other side of the pipe
failed).

This commit adds tests that expose these issues in the nix-store
commands, and fixes them for all three.

3 files changed, 5 insertions, 1 deletions

diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 950e6362a245..9e2a502afaf8 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -67,7 +67,8 @@ void FdSink::write(const unsigned char * data, size_t len)
     try {
         writeFull(fd, data, len);
     } catch (SysError & e) {
-        _good = true;
+        _good = false;
+        throw;
     }
 }
 
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 4fc3421c0dde..4bea1316134e 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -631,6 +631,7 @@ static void opDump(Strings opFlags, Strings opArgs)
     FdSink sink(STDOUT_FILENO);
     string path = *opArgs.begin();
     dumpPath(path, sink);
+    sink.flush();
 }
 
 
@@ -656,6 +657,7 @@ static void opExport(Strings opFlags, Strings opArgs)
 
     FdSink sink(STDOUT_FILENO);
     store->exportPaths(opArgs, sink);
+    sink.flush();
 }
 
 
diff --git a/src/nix/dump-path.cc b/src/nix/dump-path.cc
index 1a1866437b07..f411c0cb7c89 100644
--- a/src/nix/dump-path.cc
+++ b/src/nix/dump-path.cc
@@ -29,6 +29,7 @@ struct CmdDumpPath : StorePathCommand
     {
         FdSink sink(STDOUT_FILENO);
         store->narFromPath(storePath, sink);
+        sink.flush();
     }
 };