Forbid impure method calls inside dev().assert()

[jridgewell]

We have a build step that removes dev().assert calls:

// input:
function hello() {
  dev().assert(ASSERTION, 'some text to describe');
}

// output:
function hello() {
  ASSERTION;
}

// v0.js:
function hello() {
}

Generally, that ASSERTION then gets removed in v0.js, because it's a useless (side-effect free) reference. But, sometimes we assert call expressions...

Now, Closure Compiler sucks pretty badly tries to decide if a method call will have a side effect. So, this will not be eliminated from the final build.

// input:
function hello() {
  dev().assert(array.includes('something'), 'some text to describe');
}

// output:
function hello() {
  array.includes('something');
}

// v0.js:
function hello() {
  array.includes('something');
}

That's no good. We know that call it totally useless, but Closure doesn't. And that useless call stays there, and over the numerous assertions we do, those bytes add up.

Proposal

From now on, any call expression inside dev().assert() must be marked as /*PURE*/:

dev().assert(array./*PURE*/includes())

dev().assert(someCheck/*PURE*/())

Using this, we will now that we can completely remove the assertion:

// input:
function hello() {
  dev().assert(array./*PURE*/includes('something'), 'some text to describe');
}

// output:
function hello() {
  undefined;
}

// v0.js:
function hello() {
}

[ampprojectbot]

This issue seems to be in Pending Triage for awhile. @jridgewell Please triage this to an appropriate milestone.

[ampprojectbot]

This issue seems to be in Pending Triage for awhile. @jridgewell Please triage this to an appropriate milestone.

[rsimha]

@jridgewell Does this issue remain with the change to @closurePrimitive annotations added in 5ebcee3#commitcomment-33643222 in #22446?

[rsimha]

Closing as stale. Please reopen if there's anything left to do.