Add support for hlsearch variable

[jphalip]

No description provided.

[citizenmatt]

This is fine, but personally, I'd prefer an implementation like I outlined in this discussion comment - implement v:hlsearch as a variable with state in VimVariableServiceBase and move state from VimSearchGroup to the variable service.

The v:hlsearch variable would then be the source of truth of whether or not highlights were active, and there wouldn't be a need to check with all editors or introduce a new API.

[citizenmatt]

As mentioned in the other PRs, extracting to a new file and splitting into separate functions would be good.

[jphalip]

I agree. I suggest we wait until the other PR for the v:register (#1046) variable is available so we can access the new Variable interface.

[AlexPl292]

Thank you for your PR!. What do you think about the @ citizenmatt suggestion?

[jphalip]

@AlexPl292 I think I understand overall @citizenmatt's suggestion: Set the highlight status into a boolean value anytime a new highlighting occurs or anytime the highlighting is cleared, so that consulting the value would not require any processing. However, I'm not totally clear on the exact way to implement this. @citizenmatt Could you share a few more details on what you have in mind?

[citizenmatt]

Sure. It's not a value that we update when a highlight is shown or hidden, it's a value we update in order to show or hide highlights. It's the flag that controls whether the highlights are shown. It defaults to true and we set it to false when we call :nohlsearch.

So, I would replace this read/write property in IjVimSearchGroup:

ideavim/src/main/java/com/maddyhome/idea/vim/newapi/IjVimSearchGroup.kt

Line 67 in 82d18cf

private var showSearchHighlight: Boolean = injector.globalOptions().hlsearch

with a read-only property, something like:

private val showSearchHighlight: Boolean
  get() = injector.globalOptions().hlsearch && injector.variableService.getNonNullVariableValue(Variable("v", "hlsearch")).asBoolean()

And then whenever we currently set showSearchHighlight, we set the v:hlsearch, either to true or false so this:

ideavim/src/main/java/com/maddyhome/idea/vim/newapi/IjVimSearchGroup.kt

Lines 132 to 135 in 82d18cf

	override fun clearSearchHighlight() {
	showSearchHighlight = false
	updateSearchHighlights(false)
	}

would be something like:

override fun clearSearchHighlight() {
  injector.variableService.storeVariable(Variable("v", "hlsearch"), false.asVimInt(), ???, ???, ???)
}

And storeVariable would update the flag and then call injector.searchGroup.updateSearchHighlights. This would be a new method added to the VimSearchGroup interface. It's already defined in VimSearchGroupBase, but not the interface.

The only tricky bit is what else to pass to storeVariable. It requires an editor, an execution context and a vim script context, and we don't have those or even need them for Vim variables. I'd be inclined to make them nullable.