Reactive declarations are reordered in compiled files and run in unexpected order

[cbxp]

Describe the bug

It seems that developer cannot control the order of execution of reactive statements prefixed with $:

Given the source (where it is very important to run init first):

  $: init(object)
  $: if (indentsLocked) {
    if (object.ridgeIndentLeft < object.width / 2) object.ridgeIndentRight = object.ridgeIndentLeft
    else object.ridgeIndentRight = object.width - object.ridgeIndentLeft
  }
  $: if (overhangsLocked) object.overhangSide = object.overhangBottom

The compiler reorders the init to be last:

	$$self.$$.update = () => {
		if ($$self.$$.dirty[0] & /*indentsLocked, object*/ 3) {
			$: if (indentsLocked) {
				if (object.ridgeIndentLeft < object.width / 2) $$invalidate(0, object.ridgeIndentRight = object.ridgeIndentLeft, object); else $$invalidate(0, object.ridgeIndentRight = object.width - object.ridgeIndentLeft, object);
				console.log(object.ridgeIndentRight);
				debugger;
			}
		}

		if ($$self.$$.dirty[0] & /*overhangsLocked, object*/ 5) {
			$: if (overhangsLocked) $$invalidate(0, object.overhangSide = object.overhangBottom, object);
		}

		if ($$self.$$.dirty[0] & /*object*/ 1) {
			$: init(object);
		}
	};

Logs
Not relevant

To Reproduce
https://svelte.dev/repl/f1ae2c3d30034d519c13cd647989d0b0?version=3.31.2

Expected behavior
Developer can control the order of execution, Preferably, the order is the same as defined in source file.

Stacktraces
If you have a stack trace to include, we recommend putting inside a <details> block for the sake of the thread's readability:

Information about your Svelte project:
System:
OS: Linux 5.4 Ubuntu 20.04.1 LTS (Focal Fossa)
CPU: (8) x64 Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
Memory: 2.97 GB / 15.59 GB
Container: Yes
Shell: 5.0.17 - /bin/bash
Binaries:
Node: 15.0.1 - /usr/local/bin/node
npm: 7.0.3 - /usr/local/bin/npm
Browsers:
Chrome: 87.0.4280.141
Firefox: 84.0.2
npmPackages:
svelte: ^3.31.2 => 3.31.2

We use snowpack (probably not relevant)

Severity
Not easy to find a workaround, because reordering of reactive statements is undocumented.

[shibusalim]

Very good

[Conduitry]

They're ordered according to the dependencies that the compiler can see in the reactive blocks. $: init(object) looks like it would depend on other blocks where object is assigned to, so it gets run later. It's not currently documented outside of issue comments, but it's not a bug.

[dummdidumm]

Following up on Conduitry's general explanation, here's how you do it in your case:

  $: init(object)
  $: if (indentsLocked) {
    changeRidgeIndentRight(object);
  }
  $: if (overhangsLocked) changeOverhangSide(object)

-> no assignment to object at the $-level, instead inside functions, which the Svelte compiler does not track for reordering.

[cbxp]

@Conduitry thanks for clarification, but what is the recommended way to enforce the correct order if compiler does it wrongly?