Say why a stream is refused (REFUSED), and try it again seldom

A receiver that took no records of a stream (a source the key may not
send as, no input of that name, an input of another shape) said nothing:
its sender heard them acknowledged, never stored, and sent them all
again every second, for ever, and its operator saw nothing. Now the
receiver answers REFUSED (0x0c: the names, and why), and the sender
sends no records for a second, then a packet of them to learn whether
they are taken now, the wait twice as long each time (64 s at most). A
refusal ends when that packet is acknowledged with no REFUSED beside, or
a record is stored. link.c says it once on stderr, as a wire says a
receiver does not take its sends; serve's input says which of the two
the app lacks.

test-link: each of the three is refused seven times in 90 s with nine
packets, and a stream refused until the app has its input goes on then,
all 200 records stored. check.py links a node to an input its receiver
lacks: said once, two packets in 2.5 s.

1 files changed, 2 insertions, 4 deletions

diff --git a/serve/serve.c b/serve/serve.c
index 969bf89..b271d14 100644
--- a/serve/serve.c
+++ b/serve/serve.c
@@ -2339,10 +2339,8 @@ static void stop_shard(Host *host) {
 static int link_input(void *context, const char *name, uint32_t shape) {
     const PureModule *m = ((Owner *)context)->executor.app.module;
     int index = pure_module_input(m, name);
-    if (index < 0 || m->input[index].kind != PURE_KIND_MESSAGE || m->input[index].keyed ||
-        pure_module_shape(m, (uint32_t)index) != shape)
-        return -1;
-    return index;
+    if (index < 0 || m->input[index].kind != PURE_KIND_MESSAGE || m->input[index].keyed) return -PURE_LINK_NO_INPUT;
+    return pure_module_shape(m, (uint32_t)index) == shape ? index : -PURE_LINK_OTHER_SHAPE;
 }
 
 /* Records a link delivered, queued at the owner as a request is: applied