`_1` suffix when converting ES6 import to ES5

[louy]

Consider this code:

import Test from 'test-file'; 
new Test();

currently it gets compiled to:

var test_file_1 = require('test-file');
new test_file_1.default();

what I would expect is this:

var Test = require('test-file').default;
new Test();

This doesn't fit with the design goals of Typescript. It also causes some problems like #6249 in tsx/jsx.
Any reason for it being the way it is?

[louy]

Same thing for non-default import.

import {Test} from 'test-file'; 
new Test();

var test_file_1 = require('test-file');
new test_file_1.Test();

[vladima]

it is done to preserve ES6 semantic for imports:

// module1
export let x = 1;
// module2
import {x} from "./module1"

During ModuleDeclarationInstantiation of module2 CreateImportBinding for x will create indirect binding to x in module1. This means that whenever x in module1 is changed module2 should see new value. If compiler will convert import {x} from "./module1" to var x = require("./module1").x it will capture initial value of x but will miss all subsequent changes. Having extra level of indirection allows to always see the actual value.

[louy]

Oh nice. I didn't know about that. So what about the _1 suffix then? Wouldn't something like test_file work just fine?

[vladima]

this is just a way TypeScript compiler generates fresh unique names, also makes it easier to visually distinguish synthesized names from user defined ones.

[abirmingham]

How can one track browser progress on supporting sourcemaps for mapping import bindings, e.g. x to x_1? Are there particular issues for this request?

EDIT: Is this the relevant issue? https://bugs.chromium.org/p/chromium/issues/detail?id=327092