Add missing fields to errors

All X11 errors have the same fields. There are no differences.

In a perfect world, the XML could thus just say "define an error" and
xcbgen would do all the rest. However, the world is imperfect and we
already have a mixture of fields defined in the XML. Some of the XML
even defines trailing padding, while most does not.

This commit makes xcbgen add all fields to X11 errors, but those that
are already defined in the XML are skipped and left as-is. Due to the
structure of the code, this requires pretending that a different XML was
read, i.e. the code now modifies the in-memory structure of ElementTree
to add the missing fields to the in-memory representation of the XML.
This is the simplest way that I found to append elements. The existing
mechanisms can only prepend fields.

The approach taken by this commit was suggested by Peter Harris. Thanks
a lot for this idea, it's a lot simpler than my previous approach.

Fixes: https://gitlab.freedesktop.org/xorg/proto/xcbproto/-/issues/16
Signed-off-by: Uli Schlachter <psychon@znc.in>

1 files changed, 10 insertions, 0 deletions

diff --git a/xcbgen/xtypes.py b/xcbgen/xtypes.py
index 3359a09..0d92f2e 100644
--- a/xcbgen/xtypes.py
+++ b/xcbgen/xtypes.py
@@ -3,6 +3,7 @@ This module contains the classes which represent XCB data types.
 '''
 from xcbgen.expr import Field, Expression
 from xcbgen.align import Alignment, AlignmentLog
+from xml.etree.ElementTree import SubElement
 import __main__
 
 verbose_align_log = False
@@ -1352,6 +1353,15 @@ class Error(ComplexType):
         if self.required_start_align is None:
             self.required_start_align = Alignment(4,0)
 
+        # All errors are basically the same, but they still got different XML
+        # for historic reasons. This 'invents' the missing parts.
+        if len(self.elt) < 1:
+            SubElement(self.elt, "field", type="CARD32", name="bad_value")
+        if len(self.elt) < 2:
+            SubElement(self.elt, "field", type="CARD16", name="minor_opcode")
+        if len(self.elt) < 3:
+            SubElement(self.elt, "field", type="CARD8", name="major_opcode")
+
     def add_opcode(self, opcode, name, main):
         self.opcodes[name] = opcode
         if main: