Compiling with --noResolve elides needed imports

[breck7]

car.ts:

export class Car {
    public beep(): void {}
}

truck.ts:

import Car = require("./car");
class Truck extends Car.Car {}
new Truck().beep();

I expected ./car to be defined in both of these scenarios but it's elided in the first:

'tsc --target es5 --module amd --noResolve truck.ts' => 'define(["require", "exports"]'

'tsc --target es5 --module amd truck.ts' => 'define(["require", "exports", "./car"]'

[danquirk]

This is exactly what --noResolve is for. From the docs in our wiki:

Do not add triple-slash references or module import targets to the list of compiled files.

What were you trying to do with it?

[breck7]

@danquirk, in a larger project we are extending a class just like in this simplified test case. I understand that TS will omit imports if the imported file only includes type info required at compile time but in this case the imported file is required at runtime.

I get the expected output even with --noResolve if I add an "amd-dependency" tag or use the import in a value position like:

import Car = require("./car");
Car;
class Truck extends Car.Car {}
new Truck().beep();

but this seems odd. Ideally there would be a command line option to tell the compiler to always force imports.

[breck7]

@danquirk I could be reading it wrong but I think the wiki seems to refer to not compiling those triple-slash references or module imports into new js files, which is what happens and what I expect. I don't understand why it would assume that the "extends" is only being used for type information, when in this case it's structural.

[danquirk]

amd-dependency is for explicitly specifying what gets emitted into the require list, regardless of other logic (specifically to override things like the omitting logic for type only imports, or non-javascript require targets that TS doesn't support). That directive is one way to 'force imports' although it isn't as convenient as some global option. But it's not clear why you actually need to force imports here since it's doing the correct thing by default (without --noResolve).

The compiler isn't omitting the import for car because it thinks it's only used in type position. As you see in your original example it gets emitted correctly when you do not use --noResolve. When you use --noResolve you've explicitly told the compiler not to emit the import for car because it was an import target (of any kind). If I use Car in a value position like you did then there is a compilation error if I also use ---noResolve.

I still don't understand why you actually need --noResolve here. It is doing exactly what it's supposed to do though.

[breck7]

Yes there is a compiler error in the output messages but the js output is fine.

I'm using --noResolve for incremental compilation in Visual Studio Code.

Without --noResolve compiler takes ~12 seconds to recompile all dependencies even though only the current file has changed. Adding --noResolve drops it to under 2 seconds.

I'm not sure if there is a better way to compile only the changed file.

[danquirk]

The compiler makes a best effort to emit in the presence of a variety of errors. But there are still errors for a reason. Sometimes the emit is still usable, sometimes it is not, it depends on the particular error(s).

[breck7]

Sorry, seems the rest of my response got cutoff.

I'm using --noResolve for incremental compilation in Visual Studio Code.

Without --noResolve compiler takes ~12 seconds to recompile all dependencies even though only the current file has changed. Adding --noResolve drops it to under 2 seconds.

I'm not sure if there is a better way to compile only the changed file.

[danquirk]

Ah, sorry, missed the expando button in your last reply. Yeah --noResolve is not really what you want to be doing here to get compile on save behavior. It's really for a very different set of scenarios.

Until VS Code has proper compile on save built in you should just use the tsc -watch (--w) option on the command line. Just run tsc -w from the folder where your tsconfig.json is and the compiler will automatically recompile files in your project as they are changed.

[breck7]

Much simpler! Thanks @danquirk

[breck7]

:( @danquirk even with watch tsc is recompiling all dependent files.

[DanielRosenwasser]

Can you elaborate? Does tsc compile dependencies on the first run, or is it only on recompilations?

[breck7]

It compiles all dependencies both on the first run and everytime a single file changes that requires that dependency.

I have a folder with the 2 files above ("car.ts" and "truck.ts"). Truck.ts imports car. When I modify truck.ts both files are recompiled.

I'm running the command: "tsc --watch"

My tsconfig.json is:

{
    "compilerOptions": {
        "target": "es5",
        "module": "amd"
    }
}

[breck7]

Output messages seem to indicate that tsc is doing an incremental compile but yet the modified timestamp on all dependencies changes.

message TS6032: File change detected. Starting incremental compilation...
message TS6042: Compilation complete. Watching for file changes.