libutil: remove sinkToSource eof callback

this is only used in one place, and only to set a nicer error message on
EndOfFile. the only caller that actually *catches* this exception should
provide an error message in that catch block rather than forcing support
for setting error message so deep into the stack. copyStorePath is never
called outside of PathSubstitutionGoal anyway, which catches everything.

Change-Id: Ifbae8706d781c388737706faf4c8a8b7917ca278

src/libstore/build/substitution-goal.cc

@@ -217,6 +217,7 @@ void PathSubstitutionGoal::tryToRun()
     promise = std::promise<void>();
 
     thr = std::thread([this]() {
+        auto & fetchPath = subPath ? *subPath : storePath;
         try {
             ReceiveInterrupts receiveInterrupts;
 
@@ -226,10 +227,17 @@ void PathSubstitutionGoal::tryToRun()
             Activity act(*logger, actSubstitute, Logger::Fields{worker.store.printStorePath(storePath), sub->getUri()});
             PushActivity pact(act.id);
 
-            copyStorePath(*sub, worker.store,
-                subPath ? *subPath : storePath, repair, sub->isTrusted ? NoCheckSigs : CheckSigs);
+            copyStorePath(
+                *sub, worker.store, fetchPath, repair, sub->isTrusted ? NoCheckSigs : CheckSigs
+            );
 
             promise.set_value();
+        } catch (const EndOfFile &) {
+            promise.set_exception(std::make_exception_ptr(EndOfFile(
+                "NAR for '%s' fetched from '%s' is incomplete",
+                sub->printStorePath(fetchPath),
+                sub->getUri()
+            )));
         } catch (...) {
             promise.set_exception(std::current_exception());
         }

src/libstore/store-api.cc

@@ -1072,8 +1072,6 @@ void copyStorePath(
         });
         TeeSink tee { sink, progressSink };
         srcStore.narFromPath(storePath, tee);
-    }, [&]() {
-           throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", srcStore.printStorePath(storePath), srcStore.getUri());
     });
 
     dstStore.addToStore(*info, *source, repair, checkSigs);

src/libutil/serialise.cc

@@ -266,20 +266,17 @@ std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun)
 }
 
 
-std::unique_ptr<Source> sinkToSource(
-    std::function<void(Sink &)> fun,
-    std::function<void()> eof)
+std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun)
 {
     struct SinkToSource : Source
     {
         typedef boost::coroutines2::coroutine<std::string> coro_t;
 
         std::function<void(Sink &)> fun;
-        std::function<void()> eof;
         std::optional<coro_t::pull_type> coro;
 
-        SinkToSource(std::function<void(Sink &)> fun, std::function<void()> eof)
-            : fun(fun), eof(eof)
+        SinkToSource(std::function<void(Sink &)> fun)
+            : fun(fun)
         {
         }
 
@@ -298,7 +295,9 @@ std::unique_ptr<Source> sinkToSource(
                 });
             }
 
-            if (!*coro) { eof(); abort(); }
+            if (!*coro) {
+                throw EndOfFile("coroutine has finished");
+            }
 
             if (pos == cur.size()) {
                 if (!cur.empty()) {
@@ -317,7 +316,7 @@ std::unique_ptr<Source> sinkToSource(
         }
     };
 
-    return std::make_unique<SinkToSource>(fun, eof);
+    return std::make_unique<SinkToSource>(fun);
 }
 
 

src/libutil/serialise.hh

@@ -338,11 +338,7 @@ std::unique_ptr<FinishSink> sourceToSink(std::function<void(Source &)> fun);
  * Convert a function that feeds data into a Sink into a Source. The
  * Source executes the function as a coroutine.
  */
-std::unique_ptr<Source> sinkToSource(
-    std::function<void(Sink &)> fun,
-    std::function<void()> eof = []() {
-        throw EndOfFile("coroutine has finished");
-    });
+std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun);
 
 
 void writePadding(size_t len, Sink & sink);

tests/functional/meson.build

@@ -182,6 +182,7 @@ functional_tests_scripts = [
   'debugger.sh',
   'test-libstoreconsumer.sh',
   'extra-sandbox-profile.sh',
+  'substitute-truncated-nar.sh',
 ]
 
 # Plugin tests require shared libraries support.

tests/functional/substitute-truncated-nar.sh

@@ -0,0 +1,29 @@
+source common.sh
+
+BINARY_CACHE=file://$cacheDir
+
+build() {
+    nix-build --no-out-link "$@" --expr 'derivation {
+        name = "text";
+        system = builtins.currentSystem;
+        builder = "/bin/sh";
+        args = [ "-c" "echo some text to make the nar less empty > $out" ];
+    }'
+}
+
+path=$(build)
+nix copy --to "$BINARY_CACHE" "$path"
+nix-collect-garbage >/dev/null 2>&1
+
+nar=0bylmx35yjy2b1b4k7gjsl7i4vc03cpmryb41grfb1mp40n3hifl.nar.xz
+
+[ -e $cacheDir/nar/$nar ] || fail "long nar missing?"
+
+xzcat $cacheDir/nar/$nar > $TEST_HOME/tmp
+truncate -s $(( $(stat -c %s $TEST_HOME/tmp) - 10 )) $TEST_HOME/tmp
+xz < $TEST_HOME/tmp > $cacheDir/nar/$nar
+
+# Copying back '$path' from the binary cache. This should fail as it is truncated
+if build --option substituters "$BINARY_CACHE" --option require-sigs false -j0; then
+    fail "Importing a truncated nar should fail"
+fi