This implements the missing step 6a of 14.7.5.6 ForIn/OfHeadEvaluation:
a. If exprValue is undefined or null, then
i. Return Completion { [[Type]]: break, [[Value]]: empty, [[Target]]: empty }.
In other words, this should just do nothing instead of throwing during
the undefined to object coercion:
for (const x in undefined);
The new default return_type argument is GetOwnPropertyReturnType::All,
which returns properties with both string and symbol keys (which is also
the default for [[OwnPropertyKeys]]). This means that in some cases we
need to iterate the ordered property table twice, as we don't store
string and symbol properties separately but symbols must - there's
certainly room for (performance) improvements here. On the other hand
this makes Reflect.ownKeys() return symbol properties now :^)
Not sure if this regressed at some point or just never worked, it
definitely wasn't tested at all. We would always return undefined when
returning from a try statement block, handler, or finalizer.
By using regex::AllFlags::SkipTrimEmptyMatches we get a null string for
unmatched capture groups, which we then turn into an undefined entry in
the result array instead of putting all matches first and appending
undefined for the remaining number of capture groups - e.g. for
/foo(ba((r)|(z)))/.exec("foobaz")
we now return
["foobaz", "baz", "z", undefined, "z"]
and not [
["foobaz", "baz", "z", "z", undefined]
Fixes part of #6042.
Also happens to fix selecting an element by ID using jQuery's $("#foo").
This fixes an issue where `undefined.foo = "bar"` would throw a
ReferenceError instead of a TypeError as undefined was also used for
truly unresolvable references (e.g. `foo() = "bar"`). I also made the
various error messages here a bit nicer, just "primitive value" is not
very helpful.
Almost a year after first working on this, it's finally done: an
implementation of Promises for LibJS! :^)
The core functionality is working and closely following the spec [1].
I mostly took the pseudo code and transformed it into C++ - if you read
and understand it, you will know how the spec implements Promises; and
if you read the spec first, the code will look very familiar.
Implemented functions are:
- Promise() constructor
- Promise.prototype.then()
- Promise.prototype.catch()
- Promise.prototype.finally()
- Promise.resolve()
- Promise.reject()
For the tests I added a new function to test-js's global object,
runQueuedPromiseJobs(), which calls vm.run_queued_promise_jobs().
By design, queued jobs normally only run after the script was fully
executed, making it improssible to test handlers in individual test()
calls by default [2].
Subsequent commits include integrations into LibWeb and js(1) -
pretty-printing, running queued promise jobs when necessary.
This has an unusual amount of dbgln() statements, all hidden behind the
PROMISE_DEBUG flag - I'm leaving them in for now as they've been very
useful while debugging this, things can get quite complex with so many
asynchronously executed functions.
I've not extensively explored use of these APIs for promise-based
functionality in LibWeb (fetch(), Notification.requestPermission()
etc.), but we'll get there in due time.
[1]: https://tc39.es/ecma262/#sec-promise-objects
[2]: https://tc39.es/ecma262/#sec-jobs-and-job-queues
This only applies to the ECMA262 parser.
This behaviour is an ECMA262-specific quirk, such references always
generate zero-length matches (even on subsequent passes).
Also adds a test in LibJS's test suite.
Fixes#6039.
The test-js program expects this to exist for 'result: "fail"' results
and would crash if any duplicated test(message) occurs, as we didn't
provide 'details' in that case.
1. Allow Value(size_t) and use it for array length properties.
If an array length can't fit in an Int32 value, we shouldn't go out of
or way to force it into one. Instead, for values above INT32_MAX,
we simply store them as Double values.
2. Switch to generic indexed property storage for large arrays.
Previously we would always allocate array storage eagerly when the
length property was set. This meant that "a.length = 0x80000000" would
trivially DOS the engine on 32-bit since we don't have that much VM.
We now switch to generic storage when changing the length moves us over
the 4M entry mark.
Fixes#5986.
The auto naming of function expressions is a purely syntactic
decision, so shouldn't be decided based on the dynamic type of
an assignment. This moves the decision making into the parser.
One icky hack is that we add a field to FunctionExpression to
indicate whether we can autoname. The real solution is to actually
generate a CompoundExpression node so that the parser can make
the correct decision, however this would have a potentially
significant run time cost.
This does not correct the behaviour for class expressions.
Patch from Anonymous.
Previously we would generate function names for anonymous functions
on every AssignmentExpression, even if we weren't assigning a function.
We were also setting names of anonymous functions in arrays, which is
apparently a SpiderMonkey specific behavior not supported by V8, JSC
or required by ECMA262. This patch removes that behavior.
This is a huge performance improvement on the CanvasCycle demo! :^)
This patch rethinks the way indexed property storage works:
Instead of having a cut-off point at 200 elements where we always move
to generic property storage, we now allow arrays to stay in simple mode
as long as we don't create a gap/hole larger than 200 elements.
We also simplify generic storage to only have a hash map (for now)
instead of juggling both a vector and a hash map. This is mostly fine
since the vast majority of arrays get to stay simple now.
This is a huge speedup on anything that uses basic JS arrays with more
than 200 elements in them. :^)
Otherwise we continuously lose the first sparse element (at index
SPARSE_ARRAY_THRESHOLD) without noticing, as we overwrite all indices
with the value at index+1.
Fixes#5884.
For various statements the spec states:
Return NormalCompletion(empty).
In those cases we have been returning undefined so far, which is
incorrect.
In other cases it states:
Return Completion(UpdateEmpty(stmtCompletion, undefined)).
Which essentially means a statement is evaluated and its completion
value returned if non-empty, and undefined otherwise.
While not actually noticeable in normal scripts as the VM's "last value"
can't be accessed from JS code directly (with the exception of eval(),
see below), it provided an inconsistent experience in the REPL:
> if (true) 42;
42
> if (true) { 42; }
undefined
This also fixes the case where eval() would return undefined if the last
executed statement is not a value-producing one:
eval("1;;;;;")
eval("1;{}")
eval("1;var a;")
As a consequence of the changes outlined above, these now all correctly
return 1.
See https://tc39.es/ecma262/#sec-block-runtime-semantics-evaluation,
"NOTE 2".
Fixes#3609.
https://tc39.es/ecma262/#sec-function.prototype.tostring - this is how
the spec wants us to do it. :^)
Also change the function name behaviour to only provide a name for
NativeFunctions, which matches other engines - presumably to not expose
Proxy objects, and to prevent "function bound foo() { [native code] }".
https://tc39.es/ecma262/#sec-properties-of-the-array-prototype-object
The Array prototype object: [...] is an Array exotic object and has the
internal methods specified for such objects.
NOTE: The Array prototype object is specified to be an Array exotic
object to ensure compatibility with ECMAScript code that was created
prior to the ECMAScript 2015 specification.
This was not implementing the following part of the spec correctly:
27. For each integer i such that i ≥ 1 and i ≤ n, do
a. Let captureI be ith element of r's captures List.
b. If captureI is undefined, let capturedValue be undefined.
Expecting a capture group match to exist for each of the RegExp's
capture groups would assert in Vector's operator[] if that's not the
case, for example:
/(foo)(bar)?/.exec("foo")
Append undefined instead.
Fixes#5256.
If we have a function as class extends value, we still cannot assume
that it has a prototype property and that property has a function or
null as its value - blindly calling to_object() on it may fail.
Fixes#5075.
