Fix AST parsing when repeated assignments occur

- Additionally fix handling of `os.environ` based version numbers and
  other assignments
- Fixes #246

Signed-off-by: Dan Ryan <dan.ryan@canonical.com>

news/246.bugfix.rst

@@ -0,0 +1 @@
+Fixed an issue in the AST parser which caused failures when parsing ``setup.py`` files with assignments (e.g. ``variable = some_value``) to the same name more than once, followed by operations on those variables (e.g. ``new_value = variable + other_variable``).

src/requirementslib/models/setup_info.py

@@ -729,14 +729,16 @@ def unmap_binops(self):
             self.binOps_map[binop] = ast_unparse(binop, analyzer=self)
 
     def match_assignment_str(self, match):
-        return next(
-            iter(k for k in self.assignments if getattr(k, "id", "") == match), None
-        )
+        matches = [k for k in self.assignments if getattr(k, "id", "") == match]
+        if matches:
+            return matches[-1]
+        return None
 
     def match_assignment_name(self, match):
-        return next(
-            iter(k for k in self.assignments if getattr(k, "id", "") == match.id), None
-        )
+        matches = [k for k in self.assignments if getattr(k, "id", "") == match.id]
+        if matches:
+            return matches[-1]
+        return None
 
     def generic_unparse(self, item):
         if any(isinstance(item, k) for k in AST_BINOP_MAP.keys()):
@@ -771,7 +773,7 @@ def unparse_Subscript(self, item):
         if isinstance(item.slice, ast.Index):
             try:
                 unparsed = unparsed[self.unparse(item.slice.value)]
-            except KeyError:
+            except (KeyError, TypeError):
                 # not everything can be looked up before runtime
                 unparsed = item
         return unparsed
@@ -838,7 +840,7 @@ def unparse_Compare(self, item):
         if isinstance(item.left, ast.Attribute) or isinstance(item.left, ast.Str):
             import importlib
 
-            left = unparse(item.left)
+            left = self.unparse(item.left)
             if "." in left:
                 name, _, val = left.rpartition(".")
                 left = getattr(importlib.import_module(name), val, left)
@@ -1002,7 +1004,7 @@ def ast_unparse(item, initial_mapping=False, analyzer=None, recurse=True):  # no
             if isinstance(item.slice, ast.Index):
                 try:
                     unparsed = unparsed[unparse(item.slice.value)]
-                except KeyError:
+                except (KeyError, TypeError):
                     # not everything can be looked up before runtime
                     unparsed = item
     elif any(isinstance(item, k) for k in AST_BINOP_MAP.keys()):

tests/fixtures/setup_py/package_with_repeated_assignments/setup.py

@@ -0,0 +1,26 @@
+import os
+
+from setuptools import find_packages, setup
+
+thisdir = os.path.abspath(os.path.dirname(__file__))
+version = os.environ["PACKAGE_VERSION"]
+
+
+def my_function(other_list):
+    entry = {"key": [{"matches": ["string 1", "string 2", "some_string"]}]}
+    matches = entry["key"][0]["matches"]
+    matches = [x for x in matches if "some_string" not in x]
+    entry["key"][0]["matches"] = matches + other_list
+
+
+setup(
+    name="test_package_with_repeated_assignments",
+    version=version,
+    description="Test package with repeated assignments and version from environment",
+    long_description="This is a package",
+    install_requires=["six",],
+    package_dir={"": "src"},
+    packages=find_packages("src"),
+    include_package_data=True,
+    zip_safe=False,
+)

tests/unit/test_setup_info.py

@@ -252,6 +252,24 @@ def test_ast_parser_handles_binops(setup_py_dir):
     assert analyzer.parse_setup_function() == parsed
 
 
+def test_ast_parser_handles_repeated_assignments(setup_py_dir):
+    target = setup_py_dir.joinpath(
+        "package_with_repeated_assignments/setup.py"
+    ).as_posix()
+    parsed = ast_parse_setup_py(target)
+    analyzer = ast_parse_file(target)
+    assert parsed["name"] == "test_package_with_repeated_assignments"
+    assert isinstance(parsed["version"], str) is False
+    assert parsed["install_requires"] == ["six"]
+    analyzer_parsed = analyzer.parse_setup_function()
+    # the versions in this instance are AST objects as they come from
+    # os.environ and will need to be parsed downstream from here, so
+    # equality comparisons will fail
+    analyzer_parsed.pop("version")
+    parsed.pop("version")
+    assert analyzer_parsed == parsed
+
+
 def test_setup_cfg_parser(setup_cfg_dir):
     setup_path = setup_cfg_dir / "package_with_multiple_extras/setup.cfg"
     if six.PY2: