quick-lint-js supports a binary log format. This document describes the format and tools used to process the format.
See ADR005 Logging and tracing for rationale.
quick-lint-js' binary log is compatible with the Common Trace Format. The format of each stream is described by a CTF metadata file.
A trace is a directory containing a metadata file and one or more stream files.
The metadata file is a text file describing the format of the stream files. The
metadata file is called metadata in the directory, as expected by
Babeltrace.
A stream file is a binary file containing logged data. Each stream file is
called thread### (where ### is one or more decimal digits).
To produce a trace with the Visual Studio Code extension, set the
quick-lint-js.tracing setting to "verbose".
To find the trace directory: Open the Command Palette (ctrl-shift-P) then type
"Developer: Open Extension Logs Folder". Open the quick-lint.quick-lint-js
directory. Traces are written into a directory named trace_%TIMESTAMP% (e.g.
trace_2022-05-17-19-41-14.zlNiwm).
There are a few tools which can consume traces produced by quick-lint-js.
Build the quick-lint-js-analyze-trace CMake target, then run it with a trace file. For example:
$ ninja -C build quick-lint-js-analyze-trace
$ ./build/tools/quick-lint-js-analyze-trace .../thread1
@0000.000000000 init version='2.4.2'
@0000.000000000 document 0x2b40027ce4c0 opened: file:///home/strager/Projects/quicklint-js/sandbox/hello.js
@0000.000000000 document 0x2b40027ce4c0 changed
3:0->3:0: 'h'
[snip]
@0000.000000000 document 0x2b40027ce4c0 changed
3:9->3:10: ''
$ ./build/tools/quick-lint-js-analyze-trace --dump-final-document-content 0x2b40027ce4c0 .../thread1
const x = 3;
x = 4;sadasdsad
hello
hellohell
The Babeltrace tool can dump traces:
$ babeltrace2 ~/.config/Code/logs/20220516T161030/exthost22/quick-lint.quick-lint-js/2022-05-17-19-29-57.zVvhTp
[16:00:00.000000000] (+?.?????????) init: { thread_id = 164877, compression_scheme = 0 }, { quick_lint_js_version = "2.4.2" }
[16:00:00.000000000] (+0.000000000) vscode_document_opened: { thread_id = 164877, compression_scheme = 0 }, { doc_id = 3221267211232, uri = { code_unit_count = 60, code_units = [ ... ] }, language_id = { code_unit_count = 15, code_units = [ ... ] }, content = { code_unit_count = 110, code_units = [ ... ] } }
[16:00:00.000000000] (+0.000000000) vscode_document_closed: { thread_id = 164877, compression_scheme = 0 }, { doc_id = 0, uri = { code_unit_count = 12, code_units = [ ... ] }, language_id = { code_unit_count = 3, code_units = [ ... ] } }
[16:00:00.000000000] (+0.000000000) vscode_document_opened: { thread_id = 164877, compression_scheme = 0 }, { doc_id = 3221267214816, uri = { code_unit_count = 59, code_units = [ ... ] }, language_id = { code_unit_count = 10, code_units = [ ... ] }, content = { code_unit_count = 35, code_units = [ ... ] } }
010 Editor is a hex editor which supports decoding file formats. trace.bt contains a plugin (template) for 010 Editor, allowing you to decode and inspect quick-lint-js trace files.