test(di): avoid pytest loader when importing modules

[P403n1x87]

We avoid the use of the pytest loader when importing a module in one of the DI tests for decorated function discovery. Because the current implementation of the pytest loader does not implement the get_code method, we cannot wrap around it to get the code object for the module before it is executed. As a workaround in tests, we temporarily remove the pytest loader so that we can import the module under "normal" conditions. Once the test is done we restore the state of the sys.meta_path list.

Checklist

• PR author has checked that all the criteria below are met
• The PR description includes an overview of the change
• The PR description articulates the motivation for the change
• The change includes tests OR the PR description describes a testing strategy
• The PR description notes risks associated with the change, if any
• Newly-added code is easy to change
• The change follows the library release note guidelines
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• Reviewer has checked that all the criteria below are met
• Title is accurate
• All changes are related to the pull request's stated goal
• Avoids breaking API changes
• Testing strategy adequately addresses listed risks
• Newly-added code is easy to change
• Release note makes sense to a user of the library
• If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• Backport labels are set in a manner that is consistent with the release branch maintenance policy

[github-actions]

CODEOWNERS have been resolved as:

tests/debugging/function/test_discovery.py                              @DataDog/debugger-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and main.

Summary

The average import time in this PR is: 244 ± 5 ms.

The average import time in main is: 244 ± 5 ms.

The import time difference between this PR and main is: 0.5 ± 0.2 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.776 ms (0.73%)

ddtrace.bootstrap.sitecustomize 1.183 ms (0.48%)

ddtrace.bootstrap.preload 1.183 ms (0.48%)

ddtrace.internal.products 1.183 ms (0.48%)

ddtrace.internal.remoteconfig.client 0.592 ms (0.24%)

ddtrace 0.593 ms (0.24%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-03-20 12:18:13

Comparing candidate commit 246d56b in PR branch test/di-no-pytest-loader with baseline commit 03bee06 in branch main.

Found 3 performance improvements and 1 performance regressions! Performance is the same for 494 metrics, 2 unstable metrics.

scenario:iast_aspects-ospathdirname_aspect

• 🟩 execution_time [-412.958ns; -349.187ns] or [-10.007%; -8.462%]

scenario:iast_aspects-ospathsplit_aspect

• 🟩 execution_time [-507.920ns; -431.431ns] or [-11.476%; -9.748%]

scenario:iast_aspects-ospathsplitdrive_aspect

• 🟩 execution_time [-285.995ns; -249.687ns] or [-9.398%; -8.205%]

scenario:iast_aspects-rsplit_aspect

• 🟥 execution_time [+132.113ns; +156.917ns] or [+7.722%; +9.172%]