Anyway way to print debug output from your external scanner?

[ahelwer]

Would be nice to see some custom output from the external scanner itself when running tree-sitter parse -d. Any way to do it?

[razzeee]

Yes, you can just use sprintf("Your log here."). The tricky part is, that it will show up at the end and not chronologically.

If you add a newline, it will be in the correct places. sprintf("Your log here.\n")

[dcreager]

I think you want printf("Your log here.\n") or fprintf(stderr, "Your log here.\n") depending on whether you want your log messages to go to stdout or stderr. (sprintf writes into a string in memory.)

[ahlinc]

You can get attention to this PR: #1187

[ahlinc]

@ahelwer If you want to depend on the -d flag for the tree-sitter parse command then #1186 is what you're looking for. And also I'm waiting for #1187 to make it even more agile and make it possible to compile printing logic in external scanners only if those are used by tree-sitter CLI commands.

/cc: @maxbrunsfeld

[ahlinc]

@mikehaertl I've checked your code and it's correct, to see the output you need to call tree-sitter parse with -d flag, in that way tree-sitter will set the env variable for its parse command. Could you share a link on a git branch with the problem code? Or showing what you'd get for a command like below:

tree-sitter parse -d <FILE> |& grep 'SCANNER DEBUG'

[mikehaertl]

Nevermind. The parser I work on still uses fixed version 0.17.3. It works with a current version.

One thing: It seems, the env var is not set for tree-sitter test -d, right? I'd find this very helpful, though. What do you think?

[danielo515]

Is this exceptionally nice feature undocumented?

[leotrs]

I do believe it is undocumented, but it just saved my life <3

[ahlinc]

@mikehaertl the env var for the test subcommand was added in #2020