Problem:
$XDG_RUNTIME_DIR may be broken on WSL, which prevents starting (and even
building) Nvim. #30282
Solution:
- When startup fails, mention the servername in the error message.
- If an autogenerated server address fails, log an error and continue
with an empty `v:servername`. It's only fatal if a user provides a bad
`--listen` or `$NVIM_LISTEN_ADDRESS` address.
Before:
$ nvim --headless --listen ./hello.sock
nvim: Failed to --listen: "address already in use"
$ NVIM_LISTEN_ADDRESS='./hello.sock' ./build/bin/nvim --headless
nvim: Failed to --listen: "address already in use"
After:
$ nvim --headless --listen ./hello.sock
nvim: Failed to --listen: address already in use: "./hello.sock"
$ NVIM_LISTEN_ADDRESS='./hello.sock' ./build/bin/nvim --headless
nvim: Failed $NVIM_LISTEN_ADDRESS: address already in use: "./hello.sock"
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