Configuration environment merging can silently be incorrect

[DianaNites]

Local disk cache file configuration seemingly does not work at all.

I have a ~/.config/sccache/config as follows

[cache.disk]
# 20GiB
size = 21474836480

Ensure no existing sccache is running

1. sccache --stop-server
2. SCCACHE_LOG=debug SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache

> SCCACHE_LOG=debug SCCACHE_START_SERVER=1 SCCACHE_NO_DAEMON=1 sccache
[2026-06-27 DEBUG sccache::config] Attempting to read config file at "/home/diana/.config/sccache/config"
[2026-06-27 INFO  sccache::server] start_server: 127.0.0.1:4226
[2026-06-27 DEBUG sccache::cache::cache] Init disk cache with dir "/home/diana/.cache/sccache", size 10737418240
[2026-06-27 INFO  sccache::server] server has setup with ReadWrite
[2026-06-27 INFO  sccache::server] server started, listening on 127.0.0.1:4226

Note the size have not been applied.

Now the following config

[cache.disk]
dir = "/home/diana/.cache/sccache2"
# 20GiB
size = 21474836480

Save for log timestamps, the output is identical as before, before dir and size have not been applied.

sccache 0.16.0 and 0.15.0

Related: #2172, closed after OP found a now non-working workaround.

[DianaNites]

Ah inspiration struck and its found it, its a problem with source merging. Having SCCACHE_DIR set in the environment and size set in the config results in the config size being ignored.