typescript + babel chokes on sourceMap

[andrenarchy]

In my project with jspm 0.17.0-beta.5 (typescript+babel), the compilation errors out with

Error on translate for src/index.ts at file:///tmp/jspm-test/src/index.ts
  TypeError: file:///tmp/jspm-test/src/index.ts: Cannot assign to read only property 'mappings' of {"version":3,"file":"index.js","sourceRoot":"","sources":["index.ts"],"names":[],"mappings":"AAAA,oBAAoB;AACpB,kBAAkB;;;;;;;;;;;;;;OAEX,EAAC,GAAG,EAAE,KAAK,EAAC,MAAM,SAAS;AAElC,MAAM,IAAI,GAAW,SAAS,CAAC;AAE/B,OAAO,CAAC,GAAG,CAAC,KAAK,EAAE,IAAI,EAAE,GAAG,CAAC,CAAC;AAE9B,CAAC;;QACC,OAAO,CAAC,GAAG,CAAC,QAAQ,CAAC,CAAC;QACtB,MAAM,KAAK,CAAC,IAAI,CAAC,CAAC;QAClB,OAAO,CAAC,GAAG,CAAC,OAAO,CAAC,CAAC;IACvB,CAAC;CAAA,CAAC,EAAE,CAAC;AAEL,OAAO,CAAC,GAAG,CAAC,KAAK,EAAE,IAAI,EAAE,GAAG,CAAC,CAAC"}
    at eval (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:7749:29)
    at File.mergeSourceMap (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:7751:11)
    at File.generate (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:7916:27)
    at File.transform (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:7787:19)
    at eval (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:3904:21)
    at File.wrap (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:7798:18)
    at Pipeline.transform (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/systemjs-babel-node.js:3901:19)
    at eval (file:///tmp/jspm-test/jspm_packages/npm/systemjs-plugin-babel@0.0.2/plugin-babel.js:133:24)

It's failing in the babel plugin but the error disappears when I set "sourceMap": false in tsconfig.json so I assume that the problem is actually in the typescript plugin (which runs before babel). Maybe you can take a look at the code? Let me know if I can be of help for tracking down the issue!

It would certainly be great to re-enable sourcemaps in my project. 😄

[frankwallis]

@guybedford - there seems to be an issue here when providing an inputSourceMap to plugin-babel. plugin-typescript is setting metadata.sourceMap to the string representation of the source map file. There have been issues in this scenario with babel5 when it needed to JSON.parse the sourceMap and provide it as object but that does not seem to fix this one. Can you confirm whether metadata.sourceMap should be string or object and I can delve a bit further?

[guybedford]

@frankwallis metadata.sourceMap should be an object. I'm including a warning for setting it as a string to be on the deprecation path. I've also fixed up the in-browser Babel source map chaining today and can confirm it's all working correctly pending the coming SystemJS release.

[frankwallis]

I think this is all now working, and I've updated the example projects to use jspm@0.17.0-beta.5.