chore(internal): remove side-effects from origin [backport #4435 to 1.6] (#4811)

## Description

Unblocks backport #4806.

Accessing attributes from a module object in Python 2 seems to cause
potential side-effects, like loading more modules. To prevent them, we
ensure that we access attributes using the object type getter to bypass
any potential methods that might trigger said side-effects.


```
>   self._origin_map = {origin(module): module for module in sys.modules.values()}
E   RuntimeError: dictionary changed size during iteration

ddtrace/internal/module.py:212: RuntimeError
```

## Checklist
- [ ] Add additional sections for `feat` and `fix` pull requests.
- [ ] [Library
documentation](https://github.com/DataDog/dd-trace-py/tree/1.x/docs)
and/or [Datadog's documentation
site](https://github.com/DataDog/documentation/) is updated. Link to doc
PR in description.

## Reviewer Checklist
- [x] Title is accurate.
- [x] Description motivates each change.
- [x] No unnecessary changes were introduced in this PR.
- [x] Avoid breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Tests provided or description of manual testing performed is
included in the code or PR.
- [ ] Release note has been added for fixes and features, or else
`changelog/no-changelog` label added.
- [x] All relevant GitHub issues are correctly linked.
- [x] Backports are identified and tagged with Mergifyio.

## Description
<!-- Briefly describe the change and why it was required. -->

<!-- If this is a breaking change, explain why it is necessary. Breaking
changes must append `!` after the type/scope. See
https://ddtrace.readthedocs.io/en/stable/contributing.html for more
details. -->

## Checklist
- [ ] Followed the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines)
when writing a release note.
- [ ] Add additional sections for `feat` and `fix` pull requests.
- [ ] [Library
documentation](https://github.com/DataDog/dd-trace-py/tree/1.x/docs)
and/or [Datadog's documentation
site](https://github.com/DataDog/documentation/) is updated. Link to doc
PR in description.

<!-- Copy and paste the relevant snippet based on the type of pull
request -->

<!-- START feat -->

## Motivation
<!-- Expand on why the change is required, include relevant context for
reviewers -->

## Design 
<!-- Include benefits from the change as well as possible drawbacks and
trade-offs -->

## Testing strategy
<!-- Describe the automated tests and/or the steps for manual testing.

<!-- END feat -->

<!-- START fix -->

## Relevant issue(s)
<!-- Link the pull request to any issues related to the fix. Use
keywords for links to automate closing the issues once the pull request
is merged. -->

## Testing strategy
<!-- Describe any added regression tests and/or the manual testing
performed. -->

<!-- END fix -->

## Reviewer Checklist
- [ ] Title is accurate.
- [ ] Description motivates each change.
- [ ] No unnecessary changes were introduced in this PR.
- [ ] Avoid breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [ ] Tests provided or description of manual testing performed is
included in the code or PR.
- [ ] Release note has been added and follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/contributing.html#Release-Note-Guidelines),
or else `changelog/no-changelog` label added.
- [ ] All relevant GitHub issues are correctly linked.
- [ ] Backports are identified and tagged with Mergifyio.

Co-authored-by: Gabriele N. Tornetta <[email protected]>

Author: Yun-Kim

ddtrace/internal/module.py

@@ -90,12 +90,14 @@ def origin(module):
     # type: (ModuleType) -> str
     """Get the origin source file of the module."""
     try:
-        orig = abspath(module.__file__)  # type: ignore[type-var]
+        # DEV: Use object.__getattribute__ to avoid potential side-effects.
+        orig = abspath(object.__getattribute__(module, "__file__"))
     except (AttributeError, TypeError):
         # Module is probably only partially initialised, so we look at its
         # spec instead
         try:
-            orig = abspath(module.__spec__.origin)  # type: ignore
+            # DEV: Use object.__getattribute__ to avoid potential side-effects.
+            orig = abspath(object.__getattribute__(module, "__spec__").origin)
         except (AttributeError, ValueError, TypeError):
             orig = None
 

tests/internal/test_module.py

@@ -281,7 +281,7 @@ def test_post_run_module_hook():
 
 
 def test_get_by_origin(module_watchdog):
-    assert module_watchdog.get_by_origin(__file__) is sys.modules[__name__]
+    assert module_watchdog.get_by_origin(__file__.replace(".pyc", ".py")) is sys.modules[__name__]
 
 
 @pytest.mark.subprocess