Assert the resolved URL, not the dial, in the Avahi discovery check

The first CI run showed the discovery half working and the check failing
anyway. `-s mdns:<name>` filters on the TXT `name` record rather than the
instance label, and avahi-publish was given only the REQUIRED `path`, so
select_server() matched nothing and no dial was ever logged -- while the
line that matters was there all along:

  I discovery: found server "..." (name: <unnamed>) at ws://10.1.0.147:8927/sendspin

That line is the better assertion as well as the passing one. It is
emitted the moment discovered_server_url() succeeds, which cannot happen
with an empty address list, which only DNSServiceQueryRecord fills -- so
it pins the compat-layer claim directly, where the dial only pinned it via
RetryPacer's schedule. The published service now carries a `name` record
too, so the -s filter is exercised rather than silently matching nothing.

The tree also stops claiming three things this makes untrue: that the
Linux dns_sd path has only been read (item 5 and the mdns_dnssd.cpp
header), that `main` does not compile on Linux (item 6), and that the
Linux dual-backend configuration is unbuilt (item 4). Item 4's is narrowed
rather than dropped -- the matrix builds that configuration and asserts
the backend list, but nothing has run `-l` or heard ALSA on Linux.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: chrisuthe

.github/workflows/ci.yml

@@ -217,9 +217,15 @@ jobs:
           trap - EXIT
 
           # Half two: a server published into the same daemon, discovered and resolved by our
-          # own dns_sd code. Nothing is listening on 8927, so the dial that follows will fail;
-          # what is being asserted is the URL, which only exists if QueryRecord answered.
-          avahi-publish -s "$instance-server" _sendspin-server._tcp 8927 'path=/sendspin' &
+          # own dns_sd code. Nothing is listening on 8927 and no dial is asserted -- what is
+          # asserted is that a ws:// URL was built at all, which takes an address, which takes
+          # a QueryRecord that answered.
+          #
+          # TXT `name` as well as the REQUIRED `path`, because -s mdns:<name> filters on the
+          # former: without it the instance resolves but matches nothing, and the filter goes
+          # untested.
+          avahi-publish -s "$instance-server" _sendspin-server._tcp 8927 \
+            'path=/sendspin' "name=$instance-server" &
           publisher=$!
           trap 'kill -TERM "$publisher" 2>/dev/null || true' EXIT
 
@@ -228,16 +234,15 @@ jobs:
           client=$!
           trap 'kill -TERM "$client" "$publisher" 2>/dev/null || true' EXIT
 
+          resolved="found server \"$instance-server\" .* at ws://"
           for _ in $(seq 1 300); do
-            if grep -q "Connecting to ws://.*(server \"$instance-server\")" discover.log; then
-              break
-            fi
+            if grep -q "$resolved" discover.log; then break; fi
             sleep 0.1
           done
           echo 'What the discovering client logged:'
           cat discover.log
-          grep -q "Connecting to ws://.*(server \"$instance-server\")" discover.log || {
-            echo '::error::the server was published but never discovered and resolved to a URL'
+          grep -q "$resolved" discover.log || {
+            echo '::error::the server was published but never resolved to a ws:// URL'
             exit 1
           }
 

docs/ROADMAP.md

@@ -195,9 +195,10 @@ through Core Audio at 48 kHz/16-bit, 44.1 kHz/32-bit and 44.1 kHz/24-bit, with e
 volume and mute, the same-format restart, a mid-stream format change, recovery from a refused
 format, and the shutdown latch. It has **not** yet been driven by a real Sendspin server, so
 the sync loop converging over a live stream, controller volume, and pause/resume/next-track
-are unproven in the field. The Linux dual-backend path (`null, stdout, alsa, portaudio`, both
-`-l` sections) is likewise unexercised — this was built and tested on macOS. Item 12's build
-matrix is where that gets closed.
+are unproven in the field. Item 12's matrix now builds the Linux dual-backend configuration
+on every push and asserts from the configure output that it really is `null, stdout, alsa,
+portaudio` — but building it is all that proves. Neither `-l` section nor a note out of
+`AlsaAudioSink` has been exercised on Linux: this was written and heard on macOS.
 
 One known rough edge, and only on Linux: `AlsaAudioSink` routes libasound's own stderr
 diagnostics through the CLI logger, but it installs that handler from its *own* `probe()`
@@ -382,11 +383,11 @@ refcount and the restart backoff are the riskiest code here and are exercised on
 on macOS. (`Impl` is factored so a fake dns_sd could drive it; that is item 12's job.) And
 the property that a per-tick redial would cancel the attempt in flight is reasoned from
 `ConnectionManager::connect_to()`'s source, not exercised — what the `RetryPacer` suite
-proves is the schedule. **The Linux path is unexercised** —
-`libavahi-compat-libdnssd` has not been run against, only read; that is item 12's build
-matrix to close, and the Avahi compat findings above are the specific thing it should
-check. A mid-session server disappearance and the reconnect-after-drop path were
-covered by unit tests rather than in the field.
+proves is the schedule. The Linux path is no longer only read: item 12's matrix advertises,
+browses and resolves through a real `avahi-daemon` on every push, which is what confirms the
+Avahi compat findings above — a `ws://` URL cannot be built without an address, so it cannot
+be logged unless `DNSServiceQueryRecord` answered. A mid-session server disappearance and the
+reconnect-after-drop path were covered by unit tests rather than in the field.
 
 ### 6. Daemonization and logging — *shipped*
 
@@ -527,10 +528,9 @@ precise about.** The code *in* this item builds warning-free and passes 148/149
 bookworm against real `libasound`, `portaudio` and `libavahi-compat-libdnssd`; the one
 failure is `LastServer.AnUnwritableDirectoryFails`, which fails only because the container
 runs as root and root ignores directory permissions — it passes as a normal user in the same
-container. But **`main` itself does not compile on Linux**, for a reason that predates this
-task: see item 12. Getting far enough to run these tests needed that break patched out in a
-throwaway copy, so "green on Linux" is a statement about this item's code, not about the
-tree.
+container. The `src/mdns_dnssd.cpp` break that made `main` itself uncompilable on Linux, and
+that had to be patched out in a throwaway copy to get this far, is fixed under item 12 — the
+whole tree now builds and tests on Linux in CI.
 
 **Two things this item does not claim.** The library's own lines are **not timestamped**
 under `-f` and cannot be, for the same missing-sink-hook reason its category cannot be

src/mdns_dnssd.cpp

@@ -26,8 +26,9 @@
 /// resolve chain on the one thread -- where the POSIX getaddrinfo() upstream's
 /// `examples/tui_client` falls back to needs a thread per lookup.
 ///
-/// The Linux half of that is read from avahi's own `compat.c` and `unsupported.c`, not run:
-/// this has only been exercised against Bonjour. See docs/ROADMAP.md item 12.
+/// That the Linux half really behaves that way is checked rather than assumed: CI advertises,
+/// browses and resolves through a real `avahi-daemon` on every push, and a resolve cannot
+/// produce a URL without an address. See docs/ROADMAP.md item 12.
 
 #include "mdns.h"