chore(iast): avoid exception when no relevant frame is found

[smola]

Follow up to #13272:

• Avoid an exception when no relevant frame is found, return a tuple of None objects instead. This was a regression in fix(iast): avoid excessive filtering of stacktrace locations #13272.

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/appsec/iast/test_stacktrace.py                                    @DataDog/asm-python
ddtrace/appsec/_iast/_stacktrace.c                                      @DataDog/asm-python
ddtrace/appsec/_iast/taint_sinks/_base.py                               @DataDog/asm-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 234 ± 5 ms.

The average import time from base is: 236 ± 4 ms.

The import time difference between this PR and base is: -1.6 ± 0.2 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.960 ms (0.84%)

ddtrace.bootstrap.sitecustomize 1.288 ms (0.55%)

ddtrace.bootstrap.preload 1.288 ms (0.55%)

ddtrace.internal.products 1.288 ms (0.55%)

ddtrace.internal.remoteconfig.client 0.643 ms (0.27%)

ddtrace 0.672 ms (0.29%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-05-07 13:12:03

Comparing candidate commit 2e501b2 in PR branch smola/fix-stacktrace-exception with baseline commit 6810265 in branch main.

Found 0 performance improvements and 4 performance regressions! Performance is the same for 509 metrics, 7 unstable metrics.

scenario:iast_aspects-lstrip_aspect

• 🟥 execution_time [+1.437µs; +1.577µs] or [+10.949%; +12.012%]

scenario:iast_aspects-replace_aspect

• 🟥 execution_time [+587.451ns; +641.622ns] or [+12.501%; +13.654%]

scenario:iast_aspects-rstrip_aspect

• 🟥 execution_time [+1.331µs; +1.476µs] or [+10.245%; +11.368%]

scenario:telemetryaddmetric-1-distribution-metric-1-times

• 🟥 execution_time [+343.054ns; +389.990ns] or [+11.522%; +13.099%]

[github-actions]

The backport to 2.21 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.21 2.21
# Navigate to the new working tree
cd .worktrees/backport-2.21
# Create a new branch
git switch --create backport-13346-to-2.21
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 2e2cb67d5483406d201263865ec042c3d45da9fe
# Push it to GitHub
git push --set-upstream origin backport-13346-to-2.21
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.21

Then, create a pull request where the base branch is 2.21 and the compare/head branch is backport-13346-to-2.21.