Add test_implementation based on test_definition

These don't work because Rope's find_implementations doesn't take a
`source` argument (unlike e.g. `code_assist`) and hence *always*
loads the file from disk, which means we can't use a "fake" module
unless we want to use `unittest.mock.patch` to override some of this
behavior, which is hacky & bad.

Author: smheidrich

test/plugins/test_implementations.py

@@ -0,0 +1,142 @@
+# Copyright 2017-2020 Palantir Technologies, Inc.
+# Copyright 2021- Python Language Server Contributors.
+
+import os
+
+import pytest
+
+from pylsp import uris
+from pylsp.plugins.rope_implementation import pylsp_implementations
+from pylsp.workspace import Document
+
+DOC_URI = uris.from_fs_path(__file__)
+DOC = """
+from abc import ABC, abstractmethod
+
+class Animal(ABC):
+    @abstractmethod
+    def breathe(self):
+        ...
+
+    @property
+    @abstractmethod
+    def size(self) -> str:
+        ...
+
+class WingedAnimal(Animal):
+    @abstractmethod
+    def fly(self, destination):
+        ...
+
+class Bird(WingedAnimal):
+    def breathe(self):
+        print("*inhales like a bird*")
+
+    def fly(self, destination):
+        print("*flies like a bird*")
+
+    @property
+    def size(self) -> str:
+        return "bird-sized"
+
+print("not a method at all")
+"""
+
+
+def test_implementations(config, workspace) -> None:
+    # Over 'fly' in WingedAnimal.fly
+    cursor_pos = {"line": 15, "character": 9}
+
+    # The implementation of 'Bird.fly'
+    def_range = {
+        "start": {"line": 22, "character": 0},
+        "end": {"line": 22, "character": 999},
+    }
+
+    workspace.put_document(DOC_URI, DOC)
+    doc = workspace.get_document(DOC_URI)
+    assert [{"uri": DOC_URI, "range": def_range}] == pylsp_implementations(
+        config, workspace, doc, cursor_pos
+    )
+
+
+def test_implementations_skipping_one_class(config, workspace) -> None:
+    # Over 'Animal.breathe'
+    cursor_pos = {"line": 15, "character": 9}
+
+    # The implementation of 'breathe', skipping intermediate classes
+    def_range = {
+        "start": {"line": 19, "character": 0},
+        "end": {"line": 19, "character": 999},
+    }
+
+    doc = Document(DOC_URI, workspace, DOC)
+    assert [{"uri": DOC_URI, "range": def_range}] == pylsp_implementations(
+        config, workspace, doc, cursor_pos
+    )
+
+
+@pytest.mark.xfail(reason="not implemented upstream (Rope)", strict=True)
+def test_property_implementations(config, workspace) -> None:
+    # Over 'Animal.size'
+    cursor_pos = {"line": 10, "character": 9}
+
+    # The property implementation 'Bird.size'
+    def_range = {
+        "start": {"line": 26, "character": 0},
+        "end": {"line": 26, "character": 999},
+    }
+
+    doc = Document(DOC_URI, workspace, DOC)
+    assert [{"uri": DOC_URI, "range": def_range}] == pylsp_implementations(
+        config, workspace, doc, cursor_pos
+    )
+
+
+def test_no_implementations_if_not_a_method(config, workspace) -> None:
+    # Over 'print(...)' call
+    cursor_pos = {"line": 26, "character": 0}
+
+    doc = Document(DOC_URI, workspace, DOC)
+    assert [] == pylsp_implementations(config, workspace, doc, cursor_pos)
+
+
+def test_document_path_implementations(
+    config, workspace, workspace_other_root_path, tmpdir
+) -> None:
+    # Create a dummy module out of the workspace's root_path and try to get
+    # a implementation on it in another file placed next to it.
+    module_content = """
+class A:
+    def f():
+"""
+
+    p = tmpdir.join("mymodule.py")
+    p.write(module_content)
+
+    # Content of doc to test implementation
+    doc_content = """
+from mymodule import A
+class B(A):
+    def f():
+"""
+    doc_path = str(tmpdir) + os.path.sep + "myfile.py"
+    doc_uri = uris.from_fs_path(doc_path)
+    doc = Document(doc_uri, workspace_other_root_path, doc_content)
+
+    # The range where f is defined in mymodule.py
+    def_range = {
+        "start": {"line": 2, "character": 0},
+        "end": {"line": 2, "character": 999},
+    }
+
+    # The position where foo is called in myfile.py
+    cursor_pos = {"line": 3, "character": 9}
+
+    # The uri for mymodule.py
+    module_path = str(p)
+    module_uri = uris.from_fs_path(module_path)
+
+    assert [{"uri": module_uri, "range": def_range}] == pylsp_implementations(
+        config, workspace, doc, cursor_pos
+    )