filetransfer: abort transfer on receiver exception

not doing this will cause transfers that had their readers disappear to
linger. with lingering transfers the curl thread can't shut down, which
will cause nix itself to not shut down until the transfer finishes some
other way (most likely network timeouts). also add a new test for this.

Change-Id: Id2401b3ac85731c824db05918d4079125be25b57

2 files changed, 33 insertions, 0 deletions

diff --git a/tests/unit/libstore/filetransfer.cc b/tests/unit/libstore/filetransfer.cc
new file mode 100644
index 000000000..192bf81ef
--- /dev/null
+++ b/tests/unit/libstore/filetransfer.cc
@@ -0,0 +1,32 @@
+#include "filetransfer.hh"
+
+#include <future>
+#include <gtest/gtest.h>
+
+using namespace std::chrono_literals;
+
+namespace nix {
+
+TEST(FileTransfer, exceptionAbortsDownload)
+{
+    struct Done
+    {};
+
+    auto ft = makeFileTransfer();
+
+    LambdaSink broken([](auto block) { throw Done(); });
+
+    ASSERT_THROW(ft->download(FileTransferRequest("file:///dev/zero"), broken), Done);
+
+    // makeFileTransfer returns a ref<>, which cannot be cleared. since we also
+    // can't default-construct it we'll have to overwrite it instead, but we'll
+    // take the raw pointer out first so we can destroy it in a detached thread
+    // (otherwise a failure will stall the process and have it killed by meson)
+    auto reset = std::async(std::launch::async, [&]() { ft = makeFileTransfer(); });
+    EXPECT_EQ(reset.wait_for(10s), std::future_status::ready);
+    // if this did time out we have to leak `reset`.
+    if (reset.wait_for(0s) == std::future_status::timeout) {
+        (void) new auto(std::move(reset));
+    }
+}
+}
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 339ac9a4a..f5355cce8 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -113,6 +113,7 @@ libstore_tests_sources = files(
   'libstore/derivation.cc',
   'libstore/derived-path.cc',
   'libstore/downstream-placeholder.cc',
+  'libstore/filetransfer.cc',
   'libstore/machines.cc',
   'libstore/nar-info-disk-cache.cc',
   'libstore/outputs-spec.cc',