pyreverse - Add project modules to sys.path (#4856)

* pyreverse - Add project modules to sys.path

- Use the fix_import_path context manager in the existing pyreverse
tests
- Style refactor:
   - Use a constant for the path
   - Move the constants closer to the top of the module
- Add a test for the fix_import_path context manager
  to ensure the project root directory is in sys.path
- Prevent re-defining from outer scope
- Add a type-hint & docstrings

Closes #2479

5 files changed, 57 insertions, 27 deletions

diff --git a/ChangeLog b/ChangeLog
index 6fc6d0f6c..99f40212d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -69,6 +69,10 @@ Release date: TBA
 ..
   Put bug fixes that should not wait for a new minor version here
 
+* Pyreverse - Add the project root directory to sys.path
+
+  Closes #2479
+
 * Don't emit ``consider-using-f-string`` if ``py-version`` is set to Python < ``3.6``.
   ``f-strings`` were added in Python ``3.6``
 
diff --git a/pylint/pyreverse/main.py b/pylint/pyreverse/main.py
index 0fe8f5f21..55e416e3b 100644
--- a/pylint/pyreverse/main.py
+++ b/pylint/pyreverse/main.py
@@ -22,11 +22,11 @@
 
   create UML diagrams for classes and modules in <packages>
 """
-import os
 import sys
 from typing import Iterable
 
 from pylint.config import ConfigurationMixIn
+from pylint.lint.utils import fix_import_path
 from pylint.pyreverse import writer
 from pylint.pyreverse.diadefslib import DiadefsHandler
 from pylint.pyreverse.inspector import Linker, project_from_files
@@ -213,20 +213,15 @@ class Run(ConfigurationMixIn):
         if not args:
             print(self.help())
             return 1
-        # insert current working directory to the python path to recognize
-        # dependencies to local modules even if cwd is not in the PYTHONPATH
-        sys.path.insert(0, os.getcwd())
-        try:
+        with fix_import_path(args):
             project = project_from_files(
                 args,
                 project_name=self.config.project,
                 black_list=self.config.ignore_list,
             )
-            linker = Linker(project, tag=True)
-            handler = DiadefsHandler(self.config)
-            diadefs = handler.get_diadefs(project, linker)
-        finally:
-            sys.path.pop(0)
+        linker = Linker(project, tag=True)
+        handler = DiadefsHandler(self.config)
+        diadefs = handler.get_diadefs(project, linker)
         writer.DiagramWriter(self.config).write(diadefs)
         return 0
 
diff --git a/tests/pyreverse/conftest.py b/tests/pyreverse/conftest.py
index cb9e0780a..9536fbcb0 100644
--- a/tests/pyreverse/conftest.py
+++ b/tests/pyreverse/conftest.py
@@ -3,6 +3,7 @@ from typing import Callable, Optional
 import pytest
 from astroid.nodes.scoped_nodes import Module
 
+from pylint.lint import fix_import_path
 from pylint.pyreverse.inspector import Project, project_from_files
 from pylint.testutils.pyreverse import PyreverseConfig
 
@@ -50,6 +51,8 @@ def get_project() -> Callable:
         def _astroid_wrapper(func: Callable, modname: str) -> Module:
             return func(modname)
 
-        return project_from_files([module], _astroid_wrapper, project_name=name)
+        with fix_import_path([module]):
+            project = project_from_files([module], _astroid_wrapper, project_name=name)
+        return project
 
     return _get_project
diff --git a/tests/pyreverse/test_main.py b/tests/pyreverse/test_main.py
new file mode 100644
index 000000000..792bcbb8b
--- /dev/null
+++ b/tests/pyreverse/test_main.py
@@ -0,0 +1,31 @@
+"""Unittest for the main module"""
+import os
+import sys
+from typing import Iterator
+
+import pytest
+
+from pylint.lint import fix_import_path
+
+TEST_DATA_DIR = os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "data"))
+PROJECT_ROOT_DIR = os.path.abspath(os.path.join(TEST_DATA_DIR, ".."))
+
+
+@pytest.fixture(params=[PROJECT_ROOT_DIR, TEST_DATA_DIR])
+def setup_path(request) -> Iterator:
+    current_sys_path = list(sys.path)
+    sys.path[:] = []
+    current_dir = os.getcwd()
+    os.chdir(request.param)
+    yield
+    os.chdir(current_dir)
+    sys.path[:] = current_sys_path
+
+
+@pytest.mark.usefixtures("setup_path")
+def test_project_root_in_sys_path():
+    """Test the context manager adds the project root directory to sys.path.
+    This should happen when pyreverse is run from any directory
+    """
+    with fix_import_path([TEST_DATA_DIR]):
+        assert sys.path == [PROJECT_ROOT_DIR]
diff --git a/tests/pyreverse/test_writer.py b/tests/pyreverse/test_writer.py
index 9826dfa39..dc6394262 100644
--- a/tests/pyreverse/test_writer.py
+++ b/tests/pyreverse/test_writer.py
@@ -51,6 +51,14 @@ _DEFAULTS = {
     "output_directory": "",
 }
 
+TEST_DATA_DIR = os.path.join(os.path.dirname(__file__), "..", "data")
+
+DOT_FILES = ["packages_No_Name.dot", "classes_No_Name.dot"]
+COLORIZED_DOT_FILES = ["packages_colorized.dot", "classes_colorized.dot"]
+VCG_FILES = ["packages_No_Name.vcg", "classes_No_Name.vcg"]
+PUML_FILES = ["packages_No_Name.puml", "classes_No_Name.puml"]
+COLORIZED_PUML_FILES = ["packages_colorized.puml", "classes_colorized.puml"]
+
 
 class Config:
     """config object for tests"""
@@ -74,17 +82,10 @@ def _file_lines(path: str) -> List[str]:
     return [line for line in lines if line]
 
 
-DOT_FILES = ["packages_No_Name.dot", "classes_No_Name.dot"]
-COLORIZED_DOT_FILES = ["packages_colorized.dot", "classes_colorized.dot"]
-VCG_FILES = ["packages_No_Name.vcg", "classes_No_Name.vcg"]
-PUML_FILES = ["packages_No_Name.puml", "classes_No_Name.puml"]
-COLORIZED_PUML_FILES = ["packages_colorized.puml", "classes_colorized.puml"]
-
-
 @pytest.fixture()
 def setup_dot(default_config: PyreverseConfig, get_project: Callable) -> Iterator:
     writer = DiagramWriter(default_config)
-    project = get_project(os.path.join(os.path.dirname(__file__), "..", "data"))
+    project = get_project(TEST_DATA_DIR)
     yield from _setup(project, default_config, writer)
 
 
@@ -93,23 +94,21 @@ def setup_colorized_dot(
     colorized_dot_config: PyreverseConfig, get_project: Callable
 ) -> Iterator:
     writer = DiagramWriter(colorized_dot_config)
-    project = get_project(
-        os.path.join(os.path.dirname(__file__), "..", "data"), name="colorized"
-    )
+    project = get_project(TEST_DATA_DIR, name="colorized")
     yield from _setup(project, colorized_dot_config, writer)
 
 
 @pytest.fixture()
 def setup_vcg(vcg_config: PyreverseConfig, get_project: Callable) -> Iterator:
     writer = DiagramWriter(vcg_config)
-    project = get_project(os.path.join(os.path.dirname(__file__), "..", "data"))
+    project = get_project(TEST_DATA_DIR)
     yield from _setup(project, vcg_config, writer)
 
 
 @pytest.fixture()
 def setup_puml(puml_config: PyreverseConfig, get_project: Callable) -> Iterator:
     writer = DiagramWriter(puml_config)
-    project = get_project(os.path.join(os.path.dirname(__file__), "..", "data"))
+    project = get_project(TEST_DATA_DIR)
     yield from _setup(project, puml_config, writer)
 
 
@@ -118,9 +117,7 @@ def setup_colorized_puml(
     colorized_puml_config: PyreverseConfig, get_project: Callable
 ) -> Iterator:
     writer = DiagramWriter(colorized_puml_config)
-    project = get_project(
-        os.path.join(os.path.dirname(__file__), "..", "data"), name="colorized"
-    )
+    project = get_project(TEST_DATA_DIR, name="colorized")
     yield from _setup(project, colorized_puml_config, writer)