Deprecated support for non-sequence __requires__.

Closes #109

newsfragments/109.feature.rst

@@ -0,0 +1 @@
+Deprecated support for non-sequence __requires__.

pip_run/scripts.py

@@ -148,16 +148,27 @@ def read_python(self):
         r"""
         >>> DepsReader("__requires__=['foo']").read()
         ['foo']
-        >>> DepsReader(r"__requires__='foo\nbar\n#baz'").read()
-        ['foo', 'bar']
         """
-        raw_reqs = suppress(ValueError)(self._read)('__requires__') or []
-        reqs_items = jaraco.text.yield_lines(raw_reqs)
-        deps = Dependencies.load(reqs_items)
+        reqs = suppress(ValueError)(self._read)('__requires__') or []
+        deps = Dependencies.load(self._compat_process(reqs))
         with contextlib.suppress(ValueError):
             deps.index_url = self._read('__index_url__')
         return deps
 
+    def _compat_process(self, reqs):
+        """
+        Deprecated support for __requires__:str
+        """
+        processed = list(jaraco.text.yield_lines(reqs))
+        if reqs == processed:
+            return reqs
+        warnings.warn(
+            "Support for string processing in __requires__ is deprecated",
+            DeprecationWarning,
+            stacklevel=1,
+        )
+        return processed
+
     def _read(self, var_name):
         """
         Read a variable from self.script by parsing the AST.

tests/test_scripts.py

@@ -80,7 +80,8 @@ def test_single_dep(self):
             __requires__='foo'
             """
         )
-        assert scripts.DepsReader(script).read() == ['foo']
+        with pytest.deprecated_call():
+            assert scripts.DepsReader(script).read() == ['foo']
 
     def test_index_url(self):
         script = textwrap.dedent(
@@ -100,7 +101,7 @@ def test_fstrings_allowed(self):
         script = DALS(
             """
             # coding: future_fstrings
-            __requires__ = 'foo'
+            __requires__ = ['foo']
             f'boo'
             f'coo'
             """