fergalmoran/ladybird
1
0
Fork 0
mirror of https://github.com/fergalmoran/ladybird.git synced 2026-01-04 07:36:50 +00:00
Code Issues Packages Projects Releases Wiki Activity

LibJS: Include identifier information in nullish property read access

Browse Source 
When a GetById / GetByValue bytecode operation results in accessing a
nullish object, we now include the name of the property and the object
being accessed in the exception message (if available). This should make
it easier to debug live websites.

For example, the following errors would all previously produce a generic
error message of "ToObject on null or undefined":

  > foo = null
  > foo.bar
  Uncaught exception:
  [TypeError] Cannot access property "bar" on null object "foo"
      at <unknown>

  > foo = { bar: undefined }
  > foo.bar.baz
  Uncaught exception:
  [TypeError] Cannot access property "baz" on undefined object "foo.bar"
      at <unknown>

Note we certainly don't capture all possible nullish property read
accesses here. This just covers cases I've seen most on live websites;
we can cover more cases as they arise.
This commit is contained in:
Timothy Flynn
2024-03-29 11:26:10 -04:00
committed by Andreas Kling
parent f6ea4bbff8
commit 9bbd3103a8
9 changed files with 137 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View File

@@ -253,13 +253,16 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
super_reference.loaded_value = dst;
return super_reference;
}
auto base = TRY(expression.object().generate_bytecode(*this)).value();
auto base_identifier = intern_identifier_for_expression(expression.object());
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
auto saved_property = Operand(allocate_register());
emit<Bytecode::Op::Mov>(saved_property, property);
auto dst = preferred_dst.has_value() ? preferred_dst.value() : Operand(allocate_register());
emit<Bytecode::Op::GetByValue>(dst, base, property);
emit<Bytecode::Op::GetByValue>(dst, base, property, move(base_identifier));
return ReferenceOperands {
.base = base,
.referenced_name = saved_property,
@@ -270,7 +273,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
if (expression.property().is_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
auto dst = preferred_dst.has_value() ? preferred_dst.value() : Operand(allocate_register());
emit_get_by_id(dst, base, identifier_table_ref);
emit_get_by_id(dst, base, identifier_table_ref, move(base_identifier));
return ReferenceOperands {
.base = base,
.referenced_identifier = identifier_table_ref,
@@ -443,6 +446,39 @@ void Generator::emit_set_variable(JS::Identifier const& identifier, Operand valu
}
}
static Optional<ByteString> expression_identifier(Expression const& expression)
{
if (expression.is_identifier()) {
auto const& identifier = static_cast<Identifier const&>(expression);
return identifier.string();
}
if (expression.is_member_expression()) {
auto const& member_expression = static_cast<MemberExpression const&>(expression);
StringBuilder builder;
if (auto identifer = expression_identifier(member_expression.object()); identifer.has_value())
builder.append(*identifer);
if (auto identifer = expression_identifier(member_expression.property()); identifer.has_value()) {
if (!builder.is_empty())
builder.append('.');
builder.append(*identifer);
}
return builder.to_byte_string();
}
return {};
}
Optional<IdentifierTableIndex> Generator::intern_identifier_for_expression(Expression const& expression)
{
if (auto identifer = expression_identifier(expression); identifer.has_value())
return intern_identifier(identifer.release_value());
return {};
}
void Generator::generate_scoped_jump(JumpType type)
{
TemporaryChange temp { m_current_unwind_context, m_current_unwind_context };
@@ -596,9 +632,9 @@ CodeGenerationErrorOr<Optional<Operand>> Generator::emit_named_evaluation_if_ano
return expression.generate_bytecode(*this, preferred_dst);
}
void Generator::emit_get_by_id(Operand dst, Operand base, IdentifierTableIndex id)
void Generator::emit_get_by_id(Operand dst, Operand base, IdentifierTableIndex property_identifier, Optional<IdentifierTableIndex> base_identifier)
{
emit<Op::GetById>(dst, base, id, m_next_property_lookup_cache++);
emit<Op::GetById>(dst, base, property_identifier, move(base_identifier), m_next_property_lookup_cache++);
}
void Generator::emit_get_by_id_with_this(Operand dst, Operand base, IdentifierTableIndex id, Operand this_value)