[Transforms] Extract transformFiles call from printFile

[rbuckton]

To reduce the number of closures created, this moves the call to transformFiles out of printFile and into the main body of printFiles.

[yuit]

how is this function used? it doesn't seems to be use in this change.

[rbuckton]

It's used for emitting declaration files: https://github.com/Microsoft/TypeScript/blob/transforms-extractFromPrinter/src/compiler/printer.ts#L197

[yuit]

It will be great if you could comment the difference between forEachEmitFile forEachExpectedEmitFile. they are quite similar at a glace

[rbuckton]

I'll add comments.

[yuit]

This is not related to this change. but just wonder why we still keep getNodeEmitFlags in the TransformationContext since it is just return node.emitFlags? we don't we change every thing to use node.emitFlags. It is just a bit confusing since in the "printers.ts" we use node.emitFlags while in some places (such as destructuring.ts we still use getNodeEmitFlags from the context

[yuit]

Clarification: printer.ts on line 224. the comment above (line 223) should be just
"// Print the souce files" instead of "// Transform and print the source files" because we have done all the transformation in line 150

[yuit]

Also to clarify: this change remove printer from being part of the chain of transformer and become it separate part of the pipeline that take in transformed source files and print them?

[rbuckton]

we don't we change every thing to use node.emitFlags

I have some stashed progress on this. The tricky part is ensuring we always read via the property, but write via setNodeEmitFlags. I've considered marking emitFlags as readonly on Node.

Clarification: printer.ts on line 224...

I'll update, thanks.

...this change remove printer from being part of the chain...

That is correct.

[yuit]

Gotcha. Others than the comments, the change looks good. 👍