Fix is_hypothesis_file internal function

 Errors in third-party extensions such as `hypothesis-trio` or
 `hypothesis-jsonschema` used to be incorrectly considered to be
 Hypothesis internal errors, which could result in confusing error.

CONTRIBUTING.rst

@@ -285,6 +285,7 @@ their individual contributions.
 * `Tyler Gibbons <https://www.github.com/kavec>`_ ([email protected])
 * `Tyler Nickerson <https://www.github.com/nmbrgts>`_
 * `Vidya Rani <https://www.github.com/vidyarani-dg>`_ ([email protected])
+* `Vincent Michel <https://www.github.com/vxgmichel>`_ ([email protected])
 * `Will Hall <https://www.github.com/wrhall>`_ ([email protected])
 * `Will Thompson <https://www.github.com/wjt>`_ ([email protected])
 * `Wilfred Hughes <https://www.github.com/wilfred>`_

hypothesis-python/RELEASE.rst

@@ -0,0 +1,5 @@
+RELEASE_TYPE: patch
+
+This patch fixes a bug where errors in third-party extensions such as :pypi:hypothesis-trio or :pypi:hypothesis-jsonschema were incorrectly considered to be Hypothesis internal errors, which could result in confusing error messages.
+
+Thanks to Vincent Michel for reporting and fixing the bug!

hypothesis-python/src/hypothesis/internal/escalation.py

@@ -17,6 +17,7 @@
 import sys
 import traceback
 from inspect import getframeinfo
+from pathlib import Path
 
 import hypothesis
 from hypothesis.errors import (
@@ -35,7 +36,7 @@ def belongs_to(package):
     if not hasattr(package, "__file__"):  # pragma: no cover
         return lambda filepath: False
 
-    root = os.path.dirname(package.__file__)
+    root = Path(package.__file__).resolve().parent
     cache = {str: {}, bytes: {}}
 
     def accept(filepath):
@@ -44,7 +45,13 @@ def accept(filepath):
             return cache[ftype][filepath]
         except KeyError:
             pass
-        result = os.path.abspath(filepath).startswith(root)
+        abspath = Path(filepath).resolve()
+        try:
+            abspath.relative_to(root)
+        except ValueError:
+            result = False
+        else:
+            result = True
         cache[ftype][filepath] = result
         return result
 

hypothesis-python/tests/cover/test_escalation.py

@@ -13,8 +13,12 @@
 #
 # END HEADER
 
+import os
+import sys
+
 import pytest
 
+import hypothesis
 import hypothesis.internal.escalation as esc
 import hypothesis.strategies as st
 from hypothesis import given
@@ -62,3 +66,25 @@ def test(i):
         test()
 
     assert count == [1]
+
+
+def test_is_hypothesis_file_not_confused_by_prefix(monkeypatch):
+    # Errors in third-party extensions such as `hypothesis-trio` or
+    # `hypothesis-jsonschema` used to be incorrectly considered to be
+    # Hypothesis internal errors, which could result in confusing error
+    # messages. This test makes sure that files like:
+    # `[...]/python3.7/site-packages/hypothesis_something/[...]`
+    # are not considered as hypothesis files.
+    root = os.path.dirname(hypothesis.__file__)
+    assert esc.is_hypothesis_file(hypothesis.__file__)
+    assert esc.is_hypothesis_file(esc.__file__)
+
+    # Ignore `Path.resolve` for python 3.5 because it is strict by default
+    # and some paths in this test are made up (this behavior has been changed
+    # since python 3.6)
+    if sys.version_info < (3, 6):
+        monkeypatch.setattr("pathlib.Path.resolve", lambda x: x, raising=False)
+
+    assert not esc.is_hypothesis_file(pytest.__file__)
+    assert not esc.is_hypothesis_file(root + "-suffix")
+    assert not esc.is_hypothesis_file(root + "-suffix/something.py")