support argument placeholder

[jiacai2050]

Close #685

[leecannon]

You need to add the option to src/config_gen/config.json then run zig build gen.

Also the default should be true to match the current behaviour.

[jiacai2050]

PTAL

[leecannon]

This isn't working correctly.

Below is the result of completion of std.debug.print, the text is what is actually inserted into the editor:

	enable_argument_placeholders true	enable_argument_placeholders false
enable_snippets true	std.debug.print(comptime fmt: []const u8, args: anytype)	std.debug.print(${})
enable_snippets false	std.debug.print(${1:comptime fmt: []const u8}, ${2:args: anytype})	std.debug.print(${})

Example:

This is what should be inserted into the editor:

	enable_argument_placeholders true	enable_argument_placeholders false
enable_snippets true	std.debug.print(comptime fmt: []const u8, args: anytype)	std.debug.print()
enable_snippets false	std.debug.print	std.debug.print

So the only combination working as expected is when both are true.

[jiacai2050]

Ooops, I have make changes to make result right, but I have one question,

when enable_snippets = true, enable_argument_placeholders = false, if we output std.debug.print(), cursor will be placed after )

If we output std.debug.print(${}), cursor will be placed after (, which is more reasonable to me.

[leecannon]

Correct, with snippets but not argument placeholders it should be std.debug.print(^) (^ used to signify cursor location after accepting completion) but what was happening was std.debug.print(${})^ with the ${} actually inserted into the document and not handled specially by the editor.

I haven't check the behaviour of the latest commit, as I'm still at work and should not even being looking at this right now :),

[leecannon]

I've added a commit which ensures the placement of the cursor is correct when argument placeholders are disabled but snippets are enabled.

This PR is looking good to merge however it won't be merged until #1311 is to prevent more conflicts building up on that PR, don't worry though it should only be a couple of days.