Support passing custom filters with the same name as built-in flags

During the lexical analysis phase, add an additional prefix for undeclared
identifiers that have the same name as built-in flags, and determine the
final filter to be used during the code generation phase based on the
context provided by the user. Pull request by Hai Zhu.

Fixes: #140
Closes: #413
Pull-request: #413
Pull-request-sha: 5e64e05

Change-Id: I021043527546e5cb39cacf0471b95f99ce41ba55

doc/build/unreleased/140.rst

@@ -0,0 +1,8 @@
+.. change::
+    :tags: bug, lexer, codegen
+    :tickets: 140
+
+    During the lexical analysis phase, add an additional prefix for undeclared
+    identifiers that have the same name as built-in flags, and determine the
+    final filter to be used during the code generation phase based on the
+    context provided by the user. Pull request by Hai Zhu.

mako/codegen.py

@@ -16,6 +16,7 @@
 from mako import filters
 from mako import parsetree
 from mako import util
+from mako.filters import DEFAULT_ESCAPE_PREFIX
 from mako.pygen import PythonPrinter
 
 
@@ -26,6 +27,7 @@
 # context itself
 TOPLEVEL_DECLARED = {"UNDEFINED", "STOP_RENDERING"}
 RESERVED_NAMES = {"context", "loop"}.union(TOPLEVEL_DECLARED)
+DEFAULT_ESCAPED_N = "%sn" % DEFAULT_ESCAPE_PREFIX
 
 
 def compile(  # noqa
@@ -522,6 +524,7 @@ def write_variable_declares(self, identifiers, toplevel=False, limit=None):
             self.printer.writeline("loop = __M_loop = runtime.LoopStack()")
 
         for ident in to_write:
+            ident = ident.replace(DEFAULT_ESCAPE_PREFIX, "")
             if ident in comp_idents:
                 comp = comp_idents[ident]
                 if comp.is_block:
@@ -785,25 +788,48 @@ def locate_encode(name):
             else:
                 return filters.DEFAULT_ESCAPES.get(name, name)
 
-        if "n" not in args:
+        filter_args = set()
+        if DEFAULT_ESCAPED_N not in args:
             if is_expression:
                 if self.compiler.pagetag:
                     args = self.compiler.pagetag.filter_args.args + args
-                if self.compiler.default_filters and "n" not in args:
+                    filter_args = set(self.compiler.pagetag.filter_args.args)
+                if (
+                    self.compiler.default_filters
+                    and DEFAULT_ESCAPED_N not in args
+                ):
                     args = self.compiler.default_filters + args
         for e in args:
-            # if filter given as a function, get just the identifier portion
-            if e == "n":
+            if e == DEFAULT_ESCAPED_N:
                 continue
+
+            if e.startswith(DEFAULT_ESCAPE_PREFIX):
+                render_e = e.replace(DEFAULT_ESCAPE_PREFIX, "")
+                is_default_filter = True
+            else:
+                render_e = e
+                is_default_filter = False
+
+            # if filter given as a function, get just the identifier portion
             m = re.match(r"(.+?)(\(.*\))", e)
             if m:
-                ident, fargs = m.group(1, 2)
-                f = locate_encode(ident)
-                e = f + fargs
+                if not is_default_filter:
+                    ident, fargs = m.group(1, 2)
+                    f = locate_encode(ident)
+                    render_e = f + fargs
+                target = "%s(%s)" % (render_e, target)
+            elif is_default_filter and e not in filter_args:
+                target = "%s(%s) if %s is not UNDEFINED else %s(%s)" % (
+                    render_e,
+                    target,
+                    render_e,
+                    locate_encode(render_e),
+                    target,
+                )
             else:
-                e = locate_encode(e)
+                e = locate_encode(render_e)
                 assert e is not None
-            target = "%s(%s)" % (e, target)
+                target = "%s(%s)" % (e, target)
         return target
 
     def visitExpression(self, node):

mako/filters.py

@@ -161,3 +161,6 @@ def htmlentityreplace_errors(ex):
     "str": "str",
     "n": "n",
 }
+
+
+DEFAULT_ESCAPE_PREFIX = "__DEFAULT_ESCAPE_"

mako/pyparser.py

@@ -18,6 +18,8 @@
 from mako import compat
 from mako import exceptions
 from mako import util
+from mako.filters import DEFAULT_ESCAPE_PREFIX
+from mako.filters import DEFAULT_ESCAPES
 
 # words that cannot be assigned to (notably
 # smaller than the total keys in __builtins__)
@@ -196,9 +198,24 @@ def visit_Tuple(self, node):
                 p.declared_identifiers
             )
             lui = self.listener.undeclared_identifiers
-            self.listener.undeclared_identifiers = lui.union(
-                p.undeclared_identifiers
+            undeclared_identifiers = lui.union(p.undeclared_identifiers)
+            conflict_identifiers = undeclared_identifiers.intersection(
+                DEFAULT_ESCAPES
             )
+            if conflict_identifiers:
+                _map = {
+                    i: DEFAULT_ESCAPE_PREFIX + i for i in conflict_identifiers
+                }
+                for i, arg in enumerate(self.listener.args):
+                    if arg in _map:
+                        self.listener.args[i] = _map[arg]
+                self.listener.undeclared_identifiers = (
+                    undeclared_identifiers.symmetric_difference(
+                        conflict_identifiers
+                    ).union(_map.values())
+                )
+            else:
+                self.listener.undeclared_identifiers = undeclared_identifiers
 
 
 class ParseFunc(_ast_util.NodeVisitor):

test/test_ast.py

@@ -285,16 +285,36 @@ def test_python_fragment(self):
 
     def test_argument_list(self):
         parsed = ast.ArgumentList(
-            "3, 5, 'hi', x+5, " "context.get('lala')", **exception_kwargs
+            "3, 5, 'hi', g+5, " "context.get('lala')", **exception_kwargs
         )
-        eq_(parsed.undeclared_identifiers, {"x", "context"})
+        eq_(parsed.undeclared_identifiers, {"g", "context"})
         eq_(
             [x for x in parsed.args],
-            ["3", "5", "'hi'", "(x + 5)", "context.get('lala')"],
+            ["3", "5", "'hi'", "(g + 5)", "context.get('lala')"],
         )
 
-        parsed = ast.ArgumentList("h", **exception_kwargs)
-        eq_(parsed.args, ["h"])
+        parsed = ast.ArgumentList("m", **exception_kwargs)
+        eq_(parsed.args, ["m"])
+
+    def test_conflict_argument_list(self):
+        parsed = ast.ArgumentList(
+            "x-2, h*2, '(u)', n+5, trim, entity, unicode, decode, str, other",
+            **exception_kwargs,
+        )
+        eq_(
+            parsed.undeclared_identifiers,
+            {
+                "__DEFAULT_ESCAPE_trim",
+                "__DEFAULT_ESCAPE_h",
+                "__DEFAULT_ESCAPE_decode",
+                "__DEFAULT_ESCAPE_unicode",
+                "__DEFAULT_ESCAPE_x",
+                "__DEFAULT_ESCAPE_str",
+                "__DEFAULT_ESCAPE_entity",
+                "__DEFAULT_ESCAPE_n",
+                "other",
+            },
+        )
 
     def test_function_decl(self):
         """test getting the arguments from a function"""

test/test_filters.py

@@ -453,3 +453,36 @@ def test_capture_ccall(self):
 
         # print t.render()
         assert flatten_result(t.render()) == "this is foo. body: ccall body"
+
+    def test_conflict_filter_ident(self):
+        class h(object):
+            foo = str
+
+        t = Template(
+            """
+X:
+    ${"asdf" | h.foo}
+"""
+        )
+        assert flatten_result(t.render(h=h)) == "X: asdf"
+
+        def h(i):
+            return str(i) + "1"
+
+        t = Template(
+            """
+        ${123 | h}
+"""
+        )
+        assert flatten_result(t.render()) == "123"
+        assert flatten_result(t.render(h=h)) == "1231"
+
+        t = Template(
+            """
+        <%def name="foo()" filter="h">
+            this is foo</%def>
+        ${foo()}
+"""
+        )
+        assert flatten_result(t.render()) == "this is foo"
+        assert flatten_result(t.render(h=h)) == "this is foo1"

test/test_lexer.py

@@ -1543,7 +1543,7 @@ def test_integration(self):
                     Text("    <tr>\n", (14, 1)),
                     ControlLine("for", "for x in j:", False, (15, 1)),
                     Text("            <td>Hello ", (16, 1)),
-                    Expression("x", ["h"], (16, 23)),
+                    Expression("x", ["__DEFAULT_ESCAPE_h"], (16, 23)),
                     Text("</td>\n", (16, 30)),
                     ControlLine("for", "endfor", True, (17, 1)),
                     Text("    </tr>\n", (18, 1)),