Sort simple expansion by parameter name length kojiromike#16

parameters are sorted by decreasing length such that we expand first
the longest names.

Signed-off-by: Philippe Ombredanne <[email protected]>

parameter_expansion/pe.py

@@ -164,11 +164,13 @@ def expand_simple(s, env):
     Uses the provided environment dict.
     Similar to ``os.path.expandvars``.
     """
-    # TODO: validate if a plain replace is really what is supposed to happen
-    # in particular simple expansion may need to happen on tokens rather than
-    # on the whole string.
-    # For instance, with foo=bar, abc$fooBAR expands to abc
-    for name, value in env.items():
+    env_by_decreasing_name_length = sorted(
+        env.items(),
+        # [0] is the name.  minus its length gets the longest first.
+        key=lambda name_value: -len(name_value[0]),
+    )
+
+    for name, value in env_by_decreasing_name_length:
         s = s.replace(f"${name}", value)
         name = "{" + name + "}"
         s = s.replace(f"${name}", value)

parameter_expansion/tests/test_pe.py

@@ -561,6 +561,13 @@ def test_expand_can_handle_nested_substitution_and_pattern_expand():
     assert expanded_var == "alpha19"
 
 
+def test_expand_simple_expands_longest_param_name_first():
+    env = dict(pkg="foo", pkgver="bar")
+    var = "$pkgver"
+    expanded_var = pex.expand(var, env=env, strict=True)
+    assert expanded_var == "bar"
+
+
 def test_tokenize_preserves_spaces():
     s = " - $parameter/$aa/${bb}   - \t- \n ${parameter/ aa /   - zz }- "
     tokens = list(parameter_expansion.pe.tokenize(s))