Logger writes to stderr not stdout?

[zaydek]

Not sure if this is intentional but the behavior slightly surprised me when I was working on something else. Here’s a minimal repro screenshot.

[kzc]

Logging to stdout would interfere with pipes between processes.

$ echo 'console.log({a: 0, a: 1 ? 2 : 3})' | esbuild --minify | node
 > <stdin>:1:19: warning: Duplicate key "a" in object literal
    1 │ console.log({a: 0, a: 1 ? 2 : 3})
      ╵                    ^
   <stdin>:1:13: note: The original "a" is here
    1 │ console.log({a: 0, a: 1 ? 2 : 3})
      ╵              ^

1 warning
{ a: 2 }

$ echo 'console.log({a: 0, a: 1 ? 2 : 3})' | esbuild --minify 2>/dev/null | node
{ a: 2 }

[zaydek]

That makes sense. This is probably intentional behavior then. Thank you -- closing.

[hardfist]

It causes problems when esbuild is used in rushjs, which detect stderr output as warning, and it will terminate build if the build process generates warning info in CI environment, and it also invalidate rushjs's build cache. microsoft/rushstack#1329

[evanw]

This is what the log level setting is for:

• silent
  Do not show any log output.

• error
  Only show errors.

• warning
  Only show warnings and errors.

• info
  Show warnings, errors, and an output file summary. This is the default log level.