PYTHON-3987 Enable coverage relative_files=true and use pyproject.toml (#1406)

Author: ShaneHarvey

.coveragerc

@@ -14,7 +14,8 @@ fi
 
 createvirtualenv "$PYTHON_BINARY" covenv
 # coverage 7.3 dropped support for Python 3.7, keep in sync with run-tests.sh
-pip install -q "coverage<7.3"
+# coverage >=5 is needed for relative_files=true.
+pip install -q "coverage>=5,<7.3"
 
 pip list
 ls -la coverage/

.evergreen/combine-coverage.sh

@@ -259,7 +259,8 @@ python -c 'import sys; print(sys.version)'
 PYTHON_IMPL=$($PYTHON -c "import platform; print(platform.python_implementation())")
 if [ -n "$COVERAGE" ] && [ "$PYTHON_IMPL" = "CPython" ]; then
     # coverage 7.3 dropped support for Python 3.7, keep in sync with combine-coverage.sh.
-    python -m pip install pytest-cov "coverage<7.3"
+    # coverage >=5 is needed for relative_files=true.
+    python -m pip install pytest-cov "coverage>=5,<7.3"
     TEST_ARGS="$TEST_ARGS --cov pymongo --cov-branch --cov-report term-missing:skip-covered"
 fi
 

.evergreen/run-tests.sh

@@ -163,3 +163,25 @@ dummy-variable-rgx = "^(_+|(_+[a-zA-Z0-9_]*[a-zA-Z0-9]+?)|dummy.*)$"
     "RET", "ARG", "F405", "B028", "PGH001", "B018", "F403", "RUF015", "E731", "B007",
     "UP031", "F401", "B023", "F811"]
 "green_framework_test.py" = ["T201"]
+
+[tool.coverage.run]
+branch = true
+source = ["pymongo", "bson", "gridfs" ]
+relative_files = true
+
+[tool.coverage.report]
+exclude_lines = [
+    "if (.*and +)*_use_c( and.*)*:",
+    "def has_c",
+    "def get_version_string",
+    "^except AttributeError:",
+    "except ImportError:",
+    "raise NotImplementedError",
+    "return NotImplemented",
+    "_use_c = true",
+    "if __name__ == '__main__':",
+    ]
+partial_branches = ["if (.*and +)*not _use_c( and.*)*:"]
+
+[tool.coverage.html]
+directory = "htmlcov"