logviewer/README.md

Rustc Log Viewer

This is a log viewer for rustc's tracing output (in JSON form). It is made for when you don't yet know in advance how you want to filter your logs, and to analyze a large amount of ouput and filter it down to what you want to see. It's a TUI, and when you apply filters they get saved to disk.

Filters rarely talk about the "nth log entry". That way they are reproducible. If you change something, rerun rustc, and gather logs again, the same set of filters will create a similar trace in the UI. That way you can compare logs.

The UI shows a kind of tree view, which you can navigate with arrow keys etc. Only top-level logs are shown. With Enter you can step into a span and see the nested logs. Press ? for all possible keyboard shortcuts. You can transform the tree in three ways:

• Delete items (alt+d): delete all matching items. If no predicate is given, match only the current item.
• Inline items (alt+r): inlining means taking items that are otherwise nested (which you normally need to navigate into) and display them at the top level.
• Edit the printing of items (alt+e): WIP

An explanation of how to target groups of logs can be found by typing ?.

Gatherling logs

To make it easy to gather logs, lv can be used as a wraper for rustc or cargo commands. It has built-in presets for sets of rustc crates you might care about, and to ensure logs don't get too large.

For example

lv types x test tests/ui/sometest.rs
lv types rustc +stage1 example.rs
lv show

Use --compiler-root to make sure links in the tui point to the right directory. And pick a nice theme!

Integration with t

I built a tool to manage temporary directories: http://github.com/jdonszelmann/t-rs. If you use that tool, you'll have a folder at ~/tempdirs. Logviewer follows that convention: if it finds that directory, logs go there.