Invalid snippet example in nested placeholder snippet

[MariaSolOs]

Related discussions

• What's the proper usage of snippet nested placeholders? neovim/neovim#36232

${1:another ${2:placeholder}} (a snippet example provided here) isn't a valid snippet according to the LSP grammar.

A placeholder node is defined as placeholder ::= '${' int ':' any '}' where any ::= tabstop | placeholder | choice | variable | text. In the provided snippet the any (after the colon) would match another (as a text node) and then parsing crashes (as expected) because the placeholder value incorrectly consists of multiple nodes.

In order to ensure consistency across editors (as a primary goal of LSP) we need to clarify the feature descriptions and/or grammar to reflect the expected capabilities.

[dbaeumer]

Nested placeholders are not supported. So we should update the grammar accordinly.

[dbaeumer]

PR welcome :-)

[MariaSolOs]

Nested placeholders are not supported. So we should update the grammar accordinly.

Has this always been the intention? The placeholder section in "Snippet syntax" explicitly says that "placeholders can be nested".

I think that the grammar is correct. The main issue that I'm pointing out here is that the example included below contains 2 nodes after the colon, which is invalid according to the grammar. However ${1:another} or ${1:${2:placeholder}} are accepted by the grammar.

[dbaeumer]

@MariaSolOs you are absolutely correct. A PR would still be great but I can make the change to the Spec as well.

[echasnovski]

The #2032 contains the minimal correction to the grammar that makes it aligned both with examples in the spec and how snippets work in VS Code.

[hrsh7th]

Although this might be an unintended behavior according to the specifications, the following snippet seems to work as intended in VSCode.

{
	"Class": {
		"prefix": "clazz",
		"body": [
			"class ${1:ClassName} ${2:extends ${3:ParentClassName} }{",
			"\t${4://body}",
			"}"
		]
	}
}