Fix parsing of section headings inside templates

see #198

mwparserfromhell/parser/ctokenizer/tok_parse.c

@@ -2632,7 +2632,11 @@ PyObject* Tokenizer_parse(Tokenizer* self, uint64_t context, int push)
                 return NULL;
         }
         else if (this == '=' && this_context & LC_TEMPLATE_PARAM_KEY) {
-            if (Tokenizer_handle_template_param_value(self))
+            if (!(self->global & GL_HEADING) && (!last || last == '\n') && next == '=') {
+                if (Tokenizer_parse_heading(self))
+                    return NULL;
+            }
+            else if (Tokenizer_handle_template_param_value(self))
                 return NULL;
         }
         else if (this == next && next == '}' && this_context & LC_TEMPLATE)
@@ -2672,7 +2676,7 @@ PyObject* Tokenizer_parse(Tokenizer* self, uint64_t context, int push)
         }
         else if (this == ']' && this_context & LC_EXT_LINK_TITLE)
             return Tokenizer_pop(self);
-        else if (this == '=' && !(self->global & GL_HEADING)) {
+        else if (this == '=' && !(self->global & GL_HEADING) && !(this_context & LC_TEMPLATE)) {
             if (!last || last == '\n') {
                 if (Tokenizer_parse_heading(self))
                     return NULL;

mwparserfromhell/parser/tokenizer.py

@@ -1326,7 +1326,10 @@ class Tokenizer(object):
             elif this == "|" and self._context & contexts.TEMPLATE:
                 self._handle_template_param()
             elif this == "=" and self._context & contexts.TEMPLATE_PARAM_KEY:
-                self._handle_template_param_value()
+                if not self._global & contexts.GL_HEADING and self._read(-1) in ("\n", self.START) and next == "=":
+                    self._parse_heading()
+                else:
+                    self._handle_template_param_value()
             elif this == next == "}" and self._context & contexts.TEMPLATE:
                 return self._handle_template_end()
             elif this == "|" and self._context & contexts.ARGUMENT_NAME:
@@ -1351,7 +1354,7 @@ class Tokenizer(object):
                 self._parse_external_link(False)
             elif this == "]" and self._context & contexts.EXT_LINK_TITLE:
                 return self._pop()
-            elif this == "=" and not self._global & contexts.GL_HEADING:
+            elif this == "=" and not self._global & contexts.GL_HEADING and not self._context & contexts.TEMPLATE:
                 if self._read(-1) in ("\n", self.START):
                     self._parse_heading()
                 else:

tests/tokenizer/templates.mwtest

@@ -695,3 +695,31 @@ name:   recursion_opens_and_closes
 label:  test potentially dangerous recursion: template openings and closings
 input:  "{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}{{x|{{x}}"
 output: [Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose(), Text(text="{{x|"), TemplateOpen(), Text(text="x"), TemplateClose()]
+
+---
+
+name:   invalid_section_level_1
+label:  level 1 headings inside a template are always invalid
+input:  "{{foo|bar\n=baz=\n}}"
+output: [TemplateOpen(), Text(text="foo"), TemplateParamSeparator(), Text(text="bar\n"), TemplateParamEquals(), Text(text="baz=\n"), TemplateClose()]
+
+---
+
+name:   section_level_2
+label:  valid level 2 heading inside a template
+input:  "{{foo|bar\n==baz==\n}}"
+output: [TemplateOpen(), Text(text="foo"), TemplateParamSeparator(), Text(text="bar\n"), HeadingStart(level=2), Text(text="baz"), HeadingEnd(), Text(text="\n"), TemplateClose()]
+
+---
+
+name:   invalid_section_level_2
+label:  invalid level 2 heading inside a template
+input:  "{{foo|bar==baz==\n}}"
+output: [TemplateOpen(), Text(text="foo"), TemplateParamSeparator(), Text(text="bar"), TemplateParamEquals(), Text(text="=baz==\n"), TemplateClose()]
+
+---
+
+name:   section_level_2_after_template_parameter
+label:  level 2 heading inside a template after a parameter
+input:  "{{foo|bar=\n==baz==\n}}"
+output: [TemplateOpen(), Text(text="foo"), TemplateParamSeparator(), Text(text="bar"), TemplateParamEquals(), Text(text="\n==baz==\n"), TemplateClose()]