SourceMap does not work on multi-line chained function call.

[yoshiokatsuneo]

SourceMap does not work well if the error happens on chained function call.
I just made a simple project like below.

index.js:

require('ts-node').register();
require('./foo');

foo.ts:

let obj:any = null;
obj
.map();

tsconfig.js generation (default)

$ tsc --init

And, I got error message like below:

$ node ./node_modules/ts-node/dist/bin.js --compilerOptions '{"strict":true}' index.js 

/private/tmp/ts3/foo.ts:4
    .map();
    ^
TypeError: Cannot read property 'map' of null
    at Object.<anonymous> (/private/tmp/ts3/foo.ts:4:5)
    at Module._compile (module.js:570:32)
    at Module.m._compile (/private/tmp/ts3/node_modules/ts-node/src/index.ts:385:23)
    at Module.m._compile (/private/tmp/ts3/node_modules/ts-node/src/index.ts:385:23)
    at Module._extensions..js (module.js:579:10)
    at require.extensions.(anonymous function) (/private/tmp/ts3/node_modules/ts-node/src/index.ts:388:12)
    at Object.require.extensions.(anonymous function) [as .ts] (/private/tmp/ts3/node_modules/ts-node/src/index.ts:388:12)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)

The message says, the error happens on line 4, column5.
But, the "foo.ts" does not have line 4, column 5. (The file is 3 lines).

The error does not happens if I set "strict: false" on tsconfig.json.

And, the error does not happens if the foo.js is like below(no multi-line chained call).

let obj:any = null;
obj.map();

I dig into the issue, and found that the issue looks happens when "originalPositionFor" of source-map npm returns null. "originalPositionFor" looks assuming source map contains for all lines' column 0. But ts-node may not have source map for all the lines.

https://github.com/mozilla/source-map/blob/75663e0187002920ad98ed1de21e54cb85114609/lib/source-map-consumer.js#L616

[blakeembrey]

I'm honestly not sure if there's anything I can fix or do different in this package. The source map comes from TypeScript and the node support for source maps comes from source-map-support. I'll leave this open though, let me know if you figure something out! 😄

[yoshiokatsuneo]

Possibly, ts-node can generate a new source-map for every line based on the source-map from typescript... But, I'm not sure whether this is the best solution...

[blakeembrey]

What would the difference be from the source map TypeScript gives me? If there's a bug, it would need to be fixed in TypeScript (once we verify it's from there and not some other issue).

[yoshiokatsuneo]

Let's say, TypeScript gives source map for line number 1,3,5. But, the source-map npm requires for all lines(1,2,3,4,5,6), and returns "null" for line number 2,4,6, if ts-node provides information only for line number 1,3,5.
So, ts-node may be able to interpolate for line number 2,4,6 from the information for line number 1,3,5.

(But, I'm not sure why source-map npm does not accept in this case...)

[cspotcode]

I've confirmed that the behavior described in this ticket no longer occurs. The line number is correct.
https://github.com/TypeStrong/ts-node-repros/tree/325
https://github.com/TypeStrong/ts-node-repros/runs/2816394149