Refactor & add tests for file simulating code

fluent.runtime/tests/__init__.py

@@ -1,7 +0,0 @@
-import os
-
-
-# Unify path separator, default path separator on Windows is \ not /
-# Needed in test_falllback.py because it uses dict + string compare to make a virtual file structure
-def normalize_path(path):
-    return "/".join(os.path.split(path))

fluent.runtime/tests/test_fallback.py

@@ -1,19 +1,8 @@
-import io
-import os
 import unittest
-from unittest import mock
-
-from . import normalize_path
+from .utils import patch_files
 
 from fluent.runtime import FluentLocalization, FluentResourceLoader
 
-ISFILE = os.path.isfile
-
-
-def patch_io(codecs_open, isfile, data):
-    isfile.side_effect = lambda p: normalize_path(p) in data or ISFILE(p)
-    codecs_open.side_effect = lambda p, _, __: io.StringIO(data[normalize_path(p)])
-
 
 class TestLocalization(unittest.TestCase):
     def test_init(self):
@@ -22,17 +11,14 @@ def test_init(self):
         )
         self.assertTrue(callable(l10n.format_value))
 
-    @mock.patch("os.path.isfile")
-    @mock.patch("codecs.open")
-    def test_bundles(self, codecs_open, isfile):
-        data = {
-            "de/one.ftl": "one = in German",
-            "de/two.ftl": "two = in German",
-            "fr/two.ftl": "three = in French",
-            "en/one.ftl": "four = exists",
-            "en/two.ftl": "five = exists",
-        }
-        patch_io(codecs_open, isfile, data)
+    @patch_files({
+        "de/one.ftl": "one = in German",
+        "de/two.ftl": "two = in German",
+        "fr/two.ftl": "three = in French",
+        "en/one.ftl": "four = exists",
+        "en/two.ftl": "five = exists",
+    })
+    def test_bundles(self):
         l10n = FluentLocalization(
             ["de", "fr", "en"], ["one.ftl", "two.ftl"], FluentResourceLoader("{locale}")
         )
@@ -56,35 +42,30 @@ def test_bundles(self, codecs_open, isfile):
         self.assertEqual(l10n.format_value("five"), "exists")
 
 
-@mock.patch("os.path.isfile")
-@mock.patch("codecs.open")
 class TestResourceLoader(unittest.TestCase):
-    def test_all_exist(self, codecs_open, isfile):
-        data = {
-            "en/one.ftl": "one = exists",
-            "en/two.ftl": "two = exists",
-        }
-        patch_io(codecs_open, isfile, data)
+    @patch_files({
+        "en/one.ftl": "one = exists",
+        "en/two.ftl": "two = exists",
+    })
+    def test_all_exist(self):
         loader = FluentResourceLoader("{locale}")
         resources_list = list(loader.resources("en", ["one.ftl", "two.ftl"]))
         self.assertEqual(len(resources_list), 1)
         resources = resources_list[0]
         self.assertEqual(len(resources), 2)
 
-    def test_one_exists(self, codecs_open, isfile):
-        data = {
-            "en/two.ftl": "two = exists",
-        }
-        patch_io(codecs_open, isfile, data)
+    @patch_files({
+        "en/two.ftl": "two = exists",
+    })
+    def test_one_exists(self):
         loader = FluentResourceLoader("{locale}")
         resources_list = list(loader.resources("en", ["one.ftl", "two.ftl"]))
         self.assertEqual(len(resources_list), 1)
         resources = resources_list[0]
         self.assertEqual(len(resources), 1)
 
-    def test_none_exist(self, codecs_open, isfile):
-        data = {}
-        patch_io(codecs_open, isfile, data)
+    @patch_files({})
+    def test_none_exist(self):
         loader = FluentResourceLoader("{locale}")
         resources_list = list(loader.resources("en", ["one.ftl", "two.ftl"]))
         self.assertEqual(len(resources_list), 0)

fluent.runtime/tests/test_utils.py

@@ -0,0 +1,39 @@
+import unittest
+from .utils import patch_files
+import os
+import codecs
+
+
+class TestFileSimulate(unittest.TestCase):
+    def test_basic(self):
+        @patch_files({
+            "the.txt": "The",
+            "en/one.txt": "One",
+            "en/two.txt": "Two"
+        })
+        def patch_me(a, b):
+            self.assertEqual(a, 10)
+            self.assertEqual(b, "b")
+            self.assertFileIs(os.path.basename(__file__), None)
+            self.assertFileIs("the.txt", "The")
+            self.assertFileIs("en/one.txt", "One")
+            self.assertFileIs("en\\one.txt", "One")
+            self.assertFileIs("en/two.txt", "Two")
+            self.assertFileIs("en\\two.txt", "Two")
+            self.assertFileIs("en/three.txt", None)
+            self.assertFileIs("en\\three.txt", None)
+        patch_me(10, "b")
+
+    def assertFileIs(self, filename, expect_contents):
+        """
+        expect_contents is None: Expect file does not exist
+        expect_contents is a str: Expect file contents to match
+        """
+        if expect_contents is None:
+            self.assertFalse(os.path.isfile(filename),
+                             "Expected " + filename + " to not exist.")
+        else:
+            self.assertTrue(os.path.isfile(filename),
+                            "Expected " + filename + " to exist.")
+            self.assertEqual(codecs.open(filename, "r", "utf-8").read(),
+                             expect_contents)

fluent.runtime/tests/utils.py

@@ -1,5 +1,61 @@
+"""Utilities for testing.
+
+Import this module before patching libraries.
+"""
+
 import textwrap
+from pathlib import PurePath
+from unittest import mock
+from io import StringIO
+import functools
 
 
 def dedent_ftl(text):
     return textwrap.dedent(f"{text.rstrip()}\n")
+
+
+# Unify path separator, default path separator on Windows is \ not /
+# Supports only relative paths
+# Needed in test_falllback.py because it uses dict + string compare to make a virtual file structure
+def _normalize_path(path):
+    path = PurePath(path)
+    if path.is_absolute():
+        raise ValueError("Absolute paths are not supported in file simulation yet. ("
+                         + str(path) + ")")
+    if "." not in path.parts and ".." not in path.parts:
+        return "/".join(PurePath(path).parts)
+    else:
+        res_parts = []
+        length = len(path.parts)
+        i = 0
+        while i < length:
+            if path.parts[i] == ".":
+                i += 1
+            elif i < length - 1 and path.parts[i+1] == "..":
+                i += 2
+            else:
+                res_parts.append(path.parts[i])
+                i += 1
+        return "/".join(res_parts)
+
+
+def patch_files(files: dict):
+    """Decorate a function to simulate files ``files`` during the function.
+
+    The keys of ``files`` are file names and must use '/' for path separator.
+    The values are file contents. Directories or relative paths are not supported.
+    Example: ``{"en/one.txt": "One", "en/two.txt": "Two"}``
+
+    The implementation may be changed to match the mechanism used.
+    """
+    if files is None:
+        files = {}
+
+    def then(func):
+        @mock.patch("os.path.isfile", side_effect=lambda p: _normalize_path(p) in files)
+        @mock.patch("codecs.open", side_effect=lambda p, _, __: StringIO(files[_normalize_path(p)]))
+        @functools.wraps(func)  # Make ret look like func to later decorators
+        def ret(*args, **kwargs):
+            func(*args[:-2], **kwargs)
+        return ret
+    return then