Idea: extend capability of `extract-sequence-expressions` or applicable rule

One class of sequence expressions missed by the extract-sequence-expressions rule (or some other rule for this purpose) is when the sequence statements are tucked into an "if expression’. For example:

let a = true;

if(console.log('one'), console.log('two'), a) {
  console.log('three')
}

This is equivalent and more clearly written as:

let a = true;

console.log('one');
console.log('two');

if (a) {
  console.log('three')
}

Javascript returns the last expression in the sequence for evaluation in the “if expression”.

[epreston]

It works well.

I’m going to write out some detailed bits so we have a good record of test overage, environment, versions.

Tested Versions

module	version
putout	“28.3.0”
@putout/plugin-extract-sequence-expressions	“3.5.0”
@putout/plugin-logical-expressions	“1.2.0”

Test Project Metrics

language	files	code	comment	blank	total
JavaScript	283	50,763	2,617	6,566	59,946

Test Detection

94 errors in 50 files

Test Detail

Test 1:

• It hoists the sequence expressions found in 'if statements" correctly
• this is the simple case found above

Test 2:

• When it is proceeded by a single line, left associating control statement with an optional BodyBlock
• It creates a BodyBlock if required, then hoists the sequence statements above leaving the condition
• preserves execution order and practical outcomes
• exposes the actual execution of the code by the runtime while improving readability

“For Statement” example for clarity:

for (let n = 0; n < t.length; n++)
  if (((i = '(' + e + ': ' + t[n] + ')'), window.matchMedia(i).matches)) return t[n];

Is transformed into the more readable equivalent:

for (let n = 0; n < t.length; n++) {
  i = '(' + e + ': ' + t[n] + ')';
  if (window.matchMedia(i).matches) return t[n];
}

[coderaiser]

I’d be excited to see if we can hoist out these sequence expressions. Helpful if someone puts a comma in the wrong place creating a sequence expression when they mean to combine a condition into a larger expression for the control block. It would be neat to hit save and see the statement get ejected above on its own line.

Landed in @putout/plugin-extract-sequence-expressions@3.5.0 🎉. Is it works for you?