this gives about 20% performance improvements on pure parsing. obviously
it'll be less on full eval, but depending on how much parsing has to be
done (eg whether nixpkgs haskell modules are included or not) it ranges
anywhere from 4% to 10% in our tests.
this has been tested with thousands of core hours of fuzz testing to
ensure that the ASTs produced by the new parser are exactly the same as
the ones produced by the old parser. error messages will
change (sometimes a lot) and are currently not perfect, but we'd rather
leave that open for improvement than having this work rot forever.
the parser modifies its inputs, which means that sharing them between
the error context reporting system and the parser itself can confuse the
reporting system. usually this led to early truncation of error context
reports which, while not dangerous, can be quite confusing.
This keeps hint messages, source location information, and source code
snippets grouped together, while making stack traces shorter (so that
more stack frames can be viewed on the same terminal).
Before:
error:
… while evaluating the attribute 'body'
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:4:3:
3|
4| body = x "x";
| ^
5| }
… from call site
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:4:10:
3|
4| body = x "x";
| ^
5| }
… while calling 'x'
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:2:7:
1| let {
2| x = arg: assert arg == "y"; 123;
| ^
3|
error: assertion '(arg == "y")' failed
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:2:12:
1| let {
2| x = arg: assert arg == "y"; 123;
| ^
3|
After:
error:
… while evaluating the attribute 'body'
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:4:3:
3|
4| body = x "x";
| ^
5| }
… from call site
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:4:10:
3|
4| body = x "x";
| ^
5| }
… while calling 'x'
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:2:7:
1| let {
2| x = arg: assert arg == "y"; 123;
| ^
3|
error: assertion '(arg == "y")' failed
at /Users/wiggles/nix/tests/functional/lang/eval-fail-assert.nix:2:12:
1| let {
2| x = arg: assert arg == "y"; 123;
| ^
3|
I think it is bad for these reasons when `tests/` contains a mix of
functional and integration tests
- Concepts is harder to understand, the documentation makes a good
unit vs functional vs integration distinction, but when the
integration tests are just two subdirs within `tests/` this is not
clear.
- Source filtering in the `flake.nix` is more complex. We need to
filter out some of the dirs from `tests/`, rather than simply pick
the dirs we want and take all of them. This is a good sign the
structure of what we are trying to do is not matching the structure
of the files.
With this change we have a clean:
```shell-session
$ git show 'HEAD:tests'
tree HEAD:tests
functional/
installer/
nixos/
```
2023-10-06 09:05:56 -04:00
Renamed from tests/lang/parse-fail-utf8.err.exp (Browse further)