[Bug] Emitter prints TemplateExpression very wrong!

[grandsong]

I found this bug when I parse some typescript code into AST (by sf = ts.createSourceFile ) and then ts.createPrinter().printFile(sf) back to typescript (not js) code again.

What's the Problem

You can reproduce this bug online with npm runkit.

Chrome is recommended.

Paste these code and click "Run".

var ts =  require("typescript")
var s = "let greeting = `Hi ${name}, how are you?`";
var sf = ts.createSourceFile('', s, ts.ScriptTarget.ES2017, true);
console.info(ts.createPrinter().printFile(sf));

The output is supposed to be the same as s. However, you will see:

"let greeting = \"Hi \"name\", how are you?\";\n"

The printed ts code for the TemplateExpression AST node is completed messed up .

Probably Helpful Info

I did my little investigation in typescript.js.

Finally, I reached the function emitLiteral where a TemplateHead node (such as that of "Hi ") is converted into a string text = getLiteralTextOfNode(node) with double quotes.

I am not sure what to edit to fix this bug. So I stopped and post this issue.

Hope someone kindly fix it.

[DanielRosenwasser]

Strangley, you don't see the same problem with transpileModule.

var ts =  require("typescript")
var s = "let greeting = `Hi ${name}, how are you?`";
console.info(ts.transpileModule(s, { compilerOptions: {target: ts.ScriptTarget.ES5}}).outputText);

@rbuckton

[rbuckton]

I believe this is because the compiler options were not passed to the printer.

[grandsong]

Transpiling to js (of many editions such as ES5, ES2017) apparently uses respective transformers. Bugs in them are fixed quickly since everyone is using.

Printing AST back to ts is quite new. It is understandable that few people (like me) use it and thus found such bugs.

However, this issue seems to reveal that all transformers for js repeatedly fixed the same bug which is orginated from "src/complier/emitter.ts".