Warn when piped data is not used #719

Today

There are two kinds of messages: info and errors.

When data is piped in and files are also given, the piped data is not used (unless a flag like --replacement-pipe says what it is for). Nothing tells about this. Only with --verbose there is a line: Piped data never used.

> cat notes.txt | rexreplace foo bar my.file
my.file

Change

Add warnings as a third kind of message, and use it for this case.

• A warning starts with 🟡 and goes to stderr.
• --quiet and --quiet-total hide it.
• It never stops the run, also not with --halt.
• --void-pipe means the piped data is not wanted, so there is no warning then.

> cat notes.txt | rexreplace foo bar my.file
 🟡 Data is piped in, but no flag tells what to do with it. It is not used.
my.file

To decide

• Empty piped data, or only a line break: is that also a warning? On the v8.0 branch it was not.

Good to know

• This was made on the v8.0 branch, which is not merged, as warn() in src/output.ts. On that branch the run stopped after the warning, which looks like a mistake.
• With --replacement-js the piped data can be used from the code as pipe, so there is no warning then.
• "Error != warning" is on the list of future ideas in the README.

Reference

This was made before, on a branch that is not merged. Look at it to see how it was done. It can not be copied as it is, as it is written for older code.

• src/output.ts lines 49-55 on v8.0: warn().
• src/cli.ts lines 412-416 on v8.0: the warning when data is piped in and files are also given. The run stops there, which looks like a mistake.