Require with non-relative path can pull in unexpected code

[robertknight]

Issue moved from http://typescript.codeplex.com/workitem/2448
If a require statement has a non-relative path (eg. require('mymod') ) then tsc will search all directories from the container of the requiring file all the way up to the file system root for a corresponding source file.

This can result in the require pulling in a completely unexpected source file.

In my scenario I had the following files:

1. /home/user/myproject/crypto.ts
2. /home/user/myproject/typings/DefinitelyTyped/node/node.d.ts
3. /home/user/myproject/lib/test.ts

test.ts uses a '' directive to reference the Node.js typings. The node.d.ts file happens to have an 'import crypto = require('crypto')' statement in it to get Node.js' crypto module.

When tsc was invoked in the 'lib' directory with 'tsc test.ts' and it encountered the node.d.ts file reference, it ended up looking for:

/home/user/myproject/typings/DefinitelyTyped/node/crypto.ts
/home/user/myproject/typings/DefinitelyTyped/crypto.ts
/home/user/myproject/typings/crypto.ts
...
/crypto.ts

Since I happened to have a file with this name in one of these parent directories, tsc ended up trying to compile that code.

This behavior doesn't feel intuitive to me. Node.js' own require statement does something similar but only looks in 'node_modules/' directories at each level, so is less likely to run into the issue.

I'm unsure of what the best behavior would be. Perhaps align the way require() works with absolute paths to match node.js?

[danquirk]

I've been bitten by this myself in a very similar scenario (using node.d.ts and "events"). Certainly seems like something that could be improved.

We'd need to figure out exactly what the best new behavior would be before we can fix this though.

[johnpryan]

I'm curious why the typescript compiler works this way. For example:

// foo.ts
export function run() {
    return 'foo';
}

// myModule/bar.ts
import foo = require('foo');
export function run() {
    return foo.run() + 'bar';
}

In this case the typescript compiler understands where foo is located and outputs:

// myModule/bar.js
var foo = require('foo');                                                

function run() {                                                         
    return foo.run() + 'bar';                                            
}                                                                        
exports.run = run;

This code is not that useful; I'm not aware of any runtimes or javascript bundlers that understand how to resolve the require('foo') statement by looking in the parent directory. Support for node_modules seems to be the correct way to resolve absolute paths.

[basarat]

I'm not aware of any runtimes or javascript bundlers that understand how to resolve the require('foo') statement by looking in the parent directory

Agreed. @danquirk Should be a bug.

[mhegazy]

this is addressed by the node module resolution enhancements in #2338.