#1573 - added convenience API

[gentledepp]

Please do not merge - test fails!

[lahma]

you should use Engine.PrepareScript(sourceCode)

[gentledepp]

aah... interesting.
Is this only for performance tests, or should we also use Engine.PrepareScript(xxx) instead of new Esprima.JavaScriptParser().ParseScript(sourceCode); in our production code?

[gentledepp]

done - does not seem to make too much of a difference though:

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
ReusingEngine	3,921.6 ns	77.99 ns	152.12 ns	0.5417	-	3.34 KB
NewEngineInstance	10,940.6 ns	216.49 ns	361.71 ns	2.7618	0.1373	16.93 KB
ShadowRealm	9,524.8 ns	189.78 ns	454.70 ns	2.2888	0.1526	14.06 KB
ReusingEngine_ParsedScript	911.0 ns	17.50 ns	15.52 ns	0.3204	0.0019	1.97 KB
NewEngineInstance_ParsedScript	5,345.5 ns	77.00 ns	94.57 ns	2.5253	0.1297	15.51 KB
ShadowRealm_ParsedScript	4,677.5 ns	71.50 ns	63.38 ns	2.0599	0.1373	12.64 KB

[lahma]

You should always prefer Engine.PrepareScript() as it's the path that will get optimizations if they are possible. When script goes through the helper we can be assured that we can take our time to analyze more try to pre-calculate things. Otherwise Jint expects that this script might not be run multiple times (it doesn't know).

I recently pushed engine construction optimizations to main so you might want to rebase against it and see if things are better. NewEngineInstance cases should be faster at least.

[lahma]

@gentledepp may I inquire the status of this PR, there's a lot of great work but still a draft and could probably land main after some tweaks?

[gentledepp]

@lahma sure I will check tomorrow.

Some tweaks === rebase && tests Green
?

[lahma]

Some tweaks === rebase && tests Green ?

Exactly, sorry for the ambiguity. The API should be sound as it reflects non-shadow version.

[gentledepp]

So... did a rebase.
Here are the updated benchmark results:

BenchmarkDotNet v0.13.7, Windows 11 (10.0.22621.2428/22H2/2022Update/SunValley2)
Intel Core i7-10750H CPU 2.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET SDK 8.0.100-preview.7.23376.3
[Host] : .NET 6.0.23 (6.0.2323.48002), X64 RyuJIT AVX2
DefaultJob : .NET 6.0.23 (6.0.2323.48002), X64 RyuJIT AVX2

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
ReusingEngine	3,612.9 ns	43.64 ns	36.44 ns	0.5417	-	3.34 KB
NewEngineInstance	8,726.6 ns	168.19 ns	241.21 ns	2.6550	0.1373	16.28 KB
ShadowRealm	8,123.6 ns	142.88 ns	200.30 ns	2.2736	0.1526	13.98 KB
ReusingEngine_ParsedScript	954.4 ns	18.56 ns	24.78 ns	0.3204	0.0019	1.97 KB
NewEngineInstance_ParsedScript	4,365.1 ns	77.92 ns	80.02 ns	2.4185	0.1144	14.86 KB
ShadowRealm_ParsedScript	4,220.9 ns	93.78 ns	272.08 ns	2.0485	0.1335	12.56 KB

[gentledepp]

Also, 19 tests still fail, but these are the same 19 tests that also fail on main

[lahma]

Are you happy with the code, should we merge?

[gentledepp]

Yes, I am quite happy with it. But I am open for suggestions.
We are still running JINT 2.x so we are not in a hurry ;-)

The only thing that came to my mind was that it might be useful to have a common interface for the Engine and the ShadowRealm as far as the convenience API goes.
Because I actually do not care what it is that evaluates my code.
But this is just a feeling - and I have no concrete scenario nor a good name for it. So I skipped this.
Also: One can still create a wrapper if that'd be required.

(Sidenote: We actually tried to migrate to 3.x but experienced evaluation timeouts since then, so we had to switch back. Cannot wait until it is actually released :-D)

[lahma]

OK, I think we can bring this in, thanks for iterating.

(Sidenote: We actually tried to migrate to 3.x but experienced evaluation timeouts since then, so we had to switch back. Cannot wait until it is actually released :-D)

Probably won't be fixed by release if there's still problems that we don't know of...