Prevent compiler from moving code from one chunk to another?

Question

I read on this answer the following statement:

"Keep in mind that the compiler can and does move code from one chunk into other chunk output files if it determines that it is only used by that chunk."

Is there any way to switch that off?

I have a 'main' chunk and an 'optional' chunk, and I'm finding the code from the optional chunk is being moved entirely into the main. My optional code will only be called from the main code, but only if it's determined that we actually want to load the optional stuff (based on a flag that's external to both.)

I want to minimize the size of the main code for cases where the optional stuff isn't needed, but it doesn't seem to be possible with closure as far as I can see.

EDIT: To split the code I use the -chunk options on the (java) commandline. The 'main' one I point at several folders ('src/Infra/*.js' etc) and use 'auto' for the numFiles for the chunk. The 'optional' I point at three specific files, no wildcard, and specify 3 as numFiles. To load the 'optional' script the 'main' writes a script tag to the page and has a Promise resolve when it loads. 'optional' is supposed to instantiate the class it defines, and push a reference to that instance to an array in the global namespace, then main reads the ref from the array, and calls an init() method on it, passing in some dependencies. Is there a better-supported (and equally compact) way of doing it?

EDIT2: in case anyone has a similar issue, I resolved it using the "nameCache" feature of uglifyjs, so the separate components don't necessarily need to be compiled at the same time.

How are you splitting your code (build tool or hand calculation)? What are you using to load your optional chunks? — Chad Killingsworth, Jul 06 '18 at 21:37
Do I read this correctly, you include the "optional" file in "main" via the use of the wildcard 'src/infa/*.js'? — John, Sep 13 '18 at 19:56
No, the optional stuff is in src/someOtherDir/ so the wildcard doesn't get it. — Jeff Boyes, Sep 14 '18 at 20:10

score 1 · Answer 1 · answered Jul 11 '18 at 12:34

The compiler does not move code "up" the module graph. What's happening is the compiler somehow believes that symbols defined in your optional chunk are directly required.

This most frequently occurs because you are using dependency management and modules. When the compiler sorts dependencies, if any of the "optional" files are directly imported via require for CommonJS, import for ES6 or goog.require for Closure. In this case the compiler adds them to the main module.

To be more specific, I'd actually have to see code.

Prevent compiler from moving code from one chunk to another?

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