This is a huge patch, I know. In hindsight this perhaps could've been
done slightly more incremental, but I started and then fixed everything
until it worked, and here we are. I tried splitting of some completely
unrelated changes into separate commits, however. Anyway.
This is a rewrite of most of Object, and by extension large parts of
Array, Proxy, Reflect, String, TypedArray, and some other things.
What we already had worked fine for about 90% of things, but getting the
last 10% right proved to be increasingly difficult with the current code
that sort of grew organically and is only very loosely based on the
spec - this became especially obvious when we started fixing a large
number of test262 failures.
Key changes include:
- 1:1 matching function names and parameters of all object-related
functions, to avoid ambiguity. Previously we had things like put(),
which the spec doesn't have - as a result it wasn't always clear which
need to be used.
- Better separation between object abstract operations and internal
methods - the former are always the same, the latter can be overridden
(and are therefore virtual). The internal methods (i.e. [[Foo]] in the
spec) are now prefixed with 'internal_' for clarity - again, it was
previously not always clear which AO a certain method represents,
get() could've been both Get and [[Get]] (I don't know which one it
was closer to right now).
Note that some of the old names have been kept until all code relying
on them is updated, but they are now simple wrappers around the
closest matching standard abstract operation.
- Simplifications of the storage layer: functions that write values to
storage are now prefixed with 'storage_' to make their purpose clear,
and as they are not part of the spec they should not contain any steps
specified by it. Much functionality is now covered by the layers above
it and was removed (e.g. handling of accessors, attribute checks).
- PropertyAttributes has been greatly simplified, and is being replaced
by PropertyDescriptor - a concept similar to the current
implementation, but more aligned with the actual spec. See the commit
message of the previous commit where it was introduced for details.
- As a bonus, and since I had to look at the spec a whole lot anyway, I
introduced more inline comments with the exact steps from the spec -
this makes it super easy to verify correctness.
- East-const all the things.
As a result of all of this, things are much more correct but a bit
slower now. Retaining speed wasn't a consideration at all, I have done
no profiling of the new code - there might be low hanging fruits, which
we can then harvest separately.
Special thanks to Idan for helping me with this by tracking down bugs,
updating everything outside of LibJS to work with these changes (LibWeb,
Spreadsheet, HackStudio), as well as providing countless patches to fix
regressions I introduced - there still are very few (we got it down to
5), but we also get many new passing test262 tests in return. :^)
Co-authored-by: Idan Horowitz <idan.horowitz@gmail.com>
These will be removed in favour of just taking the argument and
'risking' a ToObject on null or undefined - this is how the spec does
it.
While that will make the message slightly less specific, it'll bring
the code closer to the spec and reduce complexity, which are both
preferable at the moment.
Doing this is a previous, separate commit is simply an attempt to make
the object rewrite commit smaller.
This would previously crash as we used to_string() without checking the
type first. Circumvent that by handling invalid and numeric ones
separately and then using to_string_or_symbol().
This is an implementation of 'The Property Descriptor Specification
Type' and related abstract operations, namely:
- IsAccessorDescriptor
- IsDataDescriptor
- IsGenericDescriptor
- FromPropertyDescriptor
- ToPropertyDescriptor
- CompletePropertyDescriptor
It works with Optional<T> to enable omitting certain fields, which will
eventually replace the Attribute::Has{Getter,Setter,Configurable,
Enumerable,Writable} bit flags, which are awkward to work with - being
able to use an initializer list with any of the possible attributes is
much more convenient.
Parts of the current PropertyAttributes implementation as well as the
much simpler PropertyDescriptor struct in Object.h will eventually be
replaced with this and completely go away.
Property storage will still use the PropertyAttributes bit flags, this
is for the layers above.
Note that this is currently guarded behind an #if 0 as if conflicts with
the existing PropertyDescriptor struct, but it's known to compile and
work just fine - I simply want to have this in a separate commit, the
primary object rewrite commit will be large enough as is.
Specifically, explicitly specify the checked type, use the resulting
value instead of doing the same calculation twice, and break down
calculations to discrete operations to ensure no intermediary overflows
are missed.
This was almost entirely up-to-spec already, just missing exception
checks, and we now leave the lexical environment in the modified state
if an exception occurs during statement evaluation.
Specifically, this now explicitly takes the length, adds missing
exceptions checks to calls with user-supplied lengths, takes and uses
the prototype argument, and fixes some spec non-conformance in
ArrayConstructor and its native functions around the use of ArrayCreate
This patch implements spec-compliant runtime semantics for the following
constructs:
- super.property
- super[property]
The MakeSuperPropertyReference AO is added to support this. :^)
ResolveBinding now matches the spec, while the non-conforming parts
are moved to GetIdentifierReference.
Implementing this properly requires variable bindings.
This is used by VM::call_internal() and VM::construct() which roughly
map to function objects' [[Call]] and [[Construct]] slots in the spec.
Reorganizing this code revealed something weird: NativeFunction gets
its strictness by checking VM::in_strict_mode(). In other words,
it inherits the strict flag from the caller context. This is quite
weird, but many test-js tests rely on it, so let's preserve it until
we can think of something nicer.
This patch adds an override for NewExpression::execute() in the AST
interpreter to separate the logic from CallExpression. As a result,
both evaluation functions are simplified.
Both expressions are still largely non-conforming, but this makes
it easier to work on improving that since we can now deal with them
separately. :^)
Specifically, instead of using the internal {get, put}_by_index methods
we now use the GetValueFromBuffer and SetValueInBuffer abstract
operations, as required by the specification.
While i was here i also replaced a couple custom detached array buffer
error messages with the existing ErrorType::DetachedArrayBuffer.
This should really be handled at a different layer of the stack, but
this allows us to make progress on the Object rewrite without breaking
strict mode assignment tests.
This code is non-conforming and will eventually get cleaned out once
we implement proper variable bindings. However, this will aid us in
improving other parts of the code right now.
This PR does not fix the main issue with our current implementation:
The specification requires that we first check the JSON string for
validity with an ECMA-404 compliant parser, and then evaluate it as if
it was javascript code, of which we do neither at the moment.
