cargo … --message-format json should tell you when it starts compiling a cate.

[bend-n]

Problem

cargo build --message-format json will have output such as:

// stdout: (none)
// stderr:
Compiling png
// stdout:
{"reason":"compiler-artifact","package-id":"png 0.17.0"} // compilation finishes

There is no way to see when png starts compiling.
The only way to find out, is to parse stderr, which also doesnt give you the full version information + manifest + etc

Proposed Solution

cargo build --message-format json will have output such as:

{"reason":"begin-compile-crate","package_id":"png 0.17.0","target":"…","features":[],"executable":null,"profile":"…"}
{"reason":"compiler-artifact","package-id":"png 0.17.0"}

[weihanglo]

Thanks for the report. The story of Cargo its own JSON message output is tracked in #8283. I'll compile them together in #8283 and close this. Thanks!