classification
Title: Trace greedy replaces $prefix and $exec_prefix
Type: Stage:
Components: Library (Lib) Versions: Python 3.9
process
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: mathstuf, vstinner
Priority: normal Keywords:

Created on 2020-02-13 08:53 by mathstuf, last changed 2020-02-17 13:51 by vstinner.

Messages (8)
msg361949 - (view) Author: Ben Boeckel (mathstuf) Date: 2020-02-13 08:53
Previously reported as a sidenote in Issue21016.

The `--ignore-dir` option in trace.py replaces `$prefix` and `$exec_prefix` *anywhere* in the path when it really should just replace it in the start of the path and if it is followed by nothing or a path separator (that is, it is a path component). I suspect that there's always a separator though.
msg361955 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2020-02-13 13:41
str.replace() can be replaced with re.sub() and \b marker.

Example:

>>> re.sub(r'\$prefix\b', '[xxx]', '$prefix $prefixpath')
'[xxx] $prefixpath'
msg361958 - (view) Author: Ben Boeckel (mathstuf) Date: 2020-02-13 15:05
`\b` is a bit too loose. That example should *not* have it replaced because it is not a full path component.

(Granted, any of these conflicting paths are "dumb" in general; I'm fine with just leaving this as a low priority, but if it does get modified, it should actually get fixed.)
msg361970 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2020-02-13 21:43
Would you mind to add examples of patterns should be replaced and patterns which should not be replaced?
msg362031 - (view) Author: Ben Boeckel (mathstuf) Date: 2020-02-15 21:23
Should be replaced (using $prefix here, but equally viable for $exec_prefix). Each quoted line is a path using a raw string.

r"$prefix"
r"$prefix/foo"

and on Windows:

r"$prefix\bar"

These should *not* be replaced:

r"$prefixvar/subdir"
r"not/a/$prefix"
r"$prefix spacevar/subdir"

because here, the `$prefix` is part of another path component. This does leave the directory literally named "$prefix" in a bit of a pickle.

Like I said, it's niche, but if we're going to fix it, let's at least consider handling more cases properly.
msg362131 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2020-02-17 09:43
> These should *not* be replaced:
>
> r"not/a/$prefix"
> r"$prefix spacevar/subdir"

Honestly, I don't see an issue to replace $prefix in these examples.

These examples seem artificial. The paths are not user provided: they are hardcoded paths from the sysconfig module:

    if opts.ignore_dir:
        _prefix = sysconfig.get_path("stdlib")
        _exec_prefix = sysconfig.get_path("platstdlib")

I'm not even sure if it's worth it to fix this issue, it's unclear to me how you could get r"$prefixvar/subdir" from sysconfig.get_path("stdlib").
msg362137 - (view) Author: Ben Boeckel (mathstuf) Date: 2020-02-17 11:31
> The paths are not user provided: they are hardcoded paths from the sysconfig module:

No, those paths are the *replacement* values, not the input. From the trace docs:

>   trace.py -c -f counts --ignore-dir '$prefix' spam.py eggs

This is the string where `$prefix` is replaced with the value retrieved from `sysconfig`.
msg362146 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2020-02-17 13:51
Do you want to propose to write a PR to fix this issue?
History
Date User Action Args
2020-02-17 13:51:48vstinnersetmessages: + msg362146
versions: + Python 3.9
2020-02-17 11:31:44mathstufsetmessages: + msg362137
2020-02-17 09:43:11vstinnersetmessages: + msg362131
2020-02-15 21:23:34mathstufsetmessages: + msg362031
2020-02-13 21:43:38vstinnersetmessages: + msg361970
2020-02-13 15:05:11mathstufsetmessages: + msg361958
2020-02-13 13:41:49vstinnersetmessages: + msg361955
2020-02-13 08:53:15mathstufcreate