Bug 780970 - Add [infallible] attribute for XPIDL attributes. r=khuey

xpcom/idl-parser/header.py

@@ -138,6 +138,11 @@ jspubtd_include = """
 #include "jspubtd.h"
 """
 
+infallible_includes = """
+#include "mozilla/Assertions.h"
+#include "mozilla/Util.h"
+"""
+
 header_end = """/* For IDL files that don't want to include root IDL files. */
 #ifndef NS_NO_VTABLE
 #define NS_NO_VTABLE
@@ -170,6 +175,13 @@ def print_header(idl, fd, filename):
     if idl.needsJSTypes():
         fd.write(jspubtd_include)
 
+    # Include some extra files if any attributes are infallible.
+    for iface in [p for p in idl.productions if p.kind == 'interface']:
+        for attr in [m for m in iface.members if isinstance(m, xpidl.Attribute)]:
+            if attr.infallible:
+                fd.write(infallible_includes)
+                break
+
     fd.write('\n')
     fd.write(header_end)
 
@@ -280,6 +292,16 @@ iface_template_epilog = """/* End of implementation class template. */
 
 """
 
+attr_infallible_tmpl = """\
+  inline %(realtype)s%(nativename)s(%(args)s)
+  {
+    %(realtype)sresult;
+    mozilla::DebugOnly<nsresult> rv = %(nativename)s(%(argnames)s&result);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+    return result;
+  }
+"""
+
 def write_interface(iface, fd):
     if iface.namemap is None:
         raise Exception("Interface was not resolved.")
@@ -310,6 +332,13 @@ def write_interface(iface, fd):
         fd.write("  /* %s */\n" % a.toIDL());
 
         fd.write("  %s = 0;\n" % attributeAsNative(a, True))
+        if a.infallible:
+            fd.write(attr_infallible_tmpl %
+                     {'realtype': a.realtype.nativeType('in'),
+                      'nativename': attributeNativeName(a, getter=True),
+                      'args': '' if not a.implicit_jscontext else 'JSContext* cx',
+                      'argnames': '' if not a.implicit_jscontext else 'cx, '})
+
         if not a.readonly:
             fd.write("  %s = 0;\n" % attributeAsNative(a, False))
         fd.write("\n")

xpcom/idl-parser/xpidl.py

@@ -715,6 +715,7 @@ class Attribute(object):
     undefined = None
     deprecated = False
     nullable = False
+    infallible = False
     defvalue = None
 
     def __init__(self, type, name, attlist, readonly, nullable, defvalue, location, doccomments):
@@ -770,6 +771,8 @@ class Attribute(object):
                     self.deprecated = True
                 elif name == 'nostdcall':
                     self.nostdcall = True
+                elif name == 'infallible':
+                    self.infallible = True
                 else:
                     raise IDLError("Unexpected attribute '%s'" % name, aloc)
 
@@ -788,6 +791,15 @@ class Attribute(object):
             getBuiltinOrNativeTypeName(self.realtype) != '[domstring]'):
             raise IDLError("Nullable types (T?) is supported only for DOMString",
                            self.location)
+        if self.infallible and not self.realtype.kind == 'builtin':
+            raise IDLError('[infallible] only works on builtin types '
+                           '(numbers, bool, and raw char types)',
+                           self.location)
+        if self.infallible and not iface.attributes.builtinclass:
+            raise IDLError('[infallible] attributes are only allowed on '
+                           '[builtinclass] interfaces',
+                           self.location)
+
 
     def toIDL(self):
         attribs = attlistToIDL(self.attlist)