From ebe3d2d3704aca001ff818295af014581dcf348f Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 21 Aug 2018 15:22:04 +0200
Subject: [PATCH] Improve 'coroutine has finished' error message

---
 src/libstore/store-api.cc |  2 ++
 src/libutil/serialise.cc  | 15 +++++++++------
 src/libutil/serialise.hh  |  6 +++++-
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 7a4a5f5eb..1f42097fc 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -609,6 +609,8 @@ void copyStorePath(ref<Store> srcStore, ref<Store> dstStore,
             act.progress(total, info->narSize);
         });
         srcStore->narFromPath({storePath}, wrapperSink);
+    }, [&]() {
+	throw EndOfFile("NAR for '%s' fetched from '%s' is incomplete", storePath, srcStore->getUri());
     });
 
     dstStore->addToStore(*info, *source, repair, checkSigs);
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index b2c49d911..17448f70e 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -161,16 +161,20 @@ size_t StringSource::read(unsigned char * data, size_t len)
 #error Coroutines are broken in this version of Boost!
 #endif
 
-std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun)
+std::unique_ptr<Source> sinkToSource(
+    std::function<void(Sink &)> fun,
+    std::function<void()> eof)
 {
     struct SinkToSource : Source
     {
         typedef boost::coroutines2::coroutine<std::string> coro_t;
 
+        std::function<void()> eof;
         coro_t::pull_type coro;
 
-        SinkToSource(std::function<void(Sink &)> fun)
-            : coro([&](coro_t::push_type & yield) {
+        SinkToSource(std::function<void(Sink &)> fun, std::function<void()> eof)
+            : eof(eof)
+            , coro([&](coro_t::push_type & yield) {
                 LambdaSink sink([&](const unsigned char * data, size_t len) {
                     if (len) yield(std::string((const char *) data, len));
                 });
@@ -184,8 +188,7 @@ std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun)
 
         size_t read(unsigned char * data, size_t len) override
         {
-            if (!coro)
-                throw EndOfFile("coroutine has finished");
+            if (!coro) { eof(); abort(); }
 
             if (pos == cur.size()) {
                 if (!cur.empty()) coro();
@@ -201,7 +204,7 @@ std::unique_ptr<Source> sinkToSource(std::function<void(Sink &)> fun)
         }
     };
 
-    return std::make_unique<SinkToSource>(fun);
+    return std::make_unique<SinkToSource>(fun, eof);
 }
 
 
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index 14b62fdb6..4b6ad5da5 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -214,7 +214,11 @@ struct LambdaSource : Source
 
 /* 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::unique_ptr<Source> sinkToSource(
+    std::function<void(Sink &)> fun,
+    std::function<void()> eof = []() {
+        throw EndOfFile("coroutine has finished");
+    });
 
 
 void writePadding(size_t len, Sink & sink);