Source map request return 500 when using MsieJavaScriptEngine

[lijunle]

After long time investigation, the following statement returns different output in IE10 and IE11:

JSXTransformer.transform("var a = <span className=\"fuck\"/>", {sourceMap:true})

In IE11, which looks fine (notices that sourceMap object is generated):

{code: "var a = Rea...", extra: Object {...}, sourceMap: Object {...}, sourceMapFilename: "source.js"}

In IE10, suck... the sourceMap gone :(

{code: "var a = Rea...", extra: Object {...}}

When using MSIE JavaScript switcher in Json.Net, it is running in ChakraActiveScript mode, its document says ChakraJsRt mode leverage IE11. While I try with this way, but it does not work, still in ChakraActiveScript mode.

Any idea on this?

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Besides, I think when send transformed JSX, it should check if it can generate source map before set the JSX header.

[Daniel15]

This is expected, the older MSIE engine can't generate source maps. The source map code in JSXTransformer has this comment above it:

// The source-map library relies on Object.defineProperty, but IE8 doesn't
// support it fully even with es5-sham. Indeed, es5-sham's defineProperty
// throws when Object.prototype.__defineGetter__ is missing, so we skip building
// the source map in that case.

JSXHandler tries the best it can to generate source maps.

I had to intentionally disable ChakraJsRt since its stack size was too small to handle transforming JSX and it kept throwing stack overflow errors. You can try to re-enable it here: https://github.com/reactjs/React.NET/blob/master/src/React/AssemblyRegistration.cs#L44-54

Besides, I think when send transformed JSX, it should check if it can generate source map before set the JSX header.

This is a good idea, I could probably just do a basic check based on the current engine - Enable it for everything except MSIE.

[Daniel15]

Also you can use the V8 engine (via React.JavaScriptEngine.ClearScriptV8 on Windows or React.JavaScriptEngine.VroomJs on Linux/Mac) which also supports source maps.

[lijunle]

@Daniel15 thanks for you advise. I may change to V8 if it is great. Besides, I have sent a PR to disable source map if it is MSIE which I have tested locally. Please take a look.

[ashic]

Is there a way to force V8 (or disabling sourcemaps for MSIE)? I couldn't find a way to specify the engine.

[domenu]

Same here, getting HTTP 500 (Unable to generate source map) in chrome...

[Daniel15]

@ashic Installing React.JavaScriptEngine.ClearScriptV8 should be sufficient to force V8.

[daniellmb]

Yep installing ClearScriptV8 fixed it for me...

[evenkiel]

+1. Installed React.JavaScriptEngine.ClearScriptV8 via nuget to my MVC project and the 500 errors went away. Thanks!

[Daniel15]

Closing this out since V8 (ClearScript / VroomJs) is bundled by default now.