Unable to write a custom lexer for simple key:value format

[andersfylling]

Hi, I'm exploring this cool project, but I'm a bit stuck and I was wondering if someone could help me understand why the following snippet is producing the error: parser_test.go:26: 1:4: invalid input text ":\"value\""?

package parser

import (
	"github.com/alecthomas/participle/v2"
	"github.com/alecthomas/participle/v2/lexer"
	"testing"
)

type Spec struct {
	Entries []*Entry `@@*`
}

type Entry struct {
	Key   string  `@ Ident ":"`
	Value *string `@String`
}

func TestParser_this_fails(t *testing.T) {
	customLexer := lexer.MustSimple([]lexer.SimpleRule{
		{"Ident", `[a-zA-Z_][a-zA-Z_0-9]*`},
		{"String", `"[^"]*"`},
	})
	p := participle.MustBuild[Spec](participle.Lexer(customLexer))
	_, err := p.ParseString("", `key:"value"`)
	if err != nil {
		t.Fatal(err)
	}
}

func TestParser_this_works(t *testing.T) {
	p := participle.MustBuild[Spec]()
	_, err := p.ParseString("", `key:"value"`)
	if err != nil {
		t.Fatal(err)
	}
}

Now if I ditch my custom lexer, it works and produces a correct AST. Using regex101 I can confirm my regex works as I expect, but I presume there's something wrong with my mental model here. Is anyone able to guide me in the right direction?

Edit: playing around with the Next method of the Lexer type, I notice that "key" is the first token returned. Given my capture group is @ Ident ":", shouldn't : be included or somehow discarded?

Edit-2: I'm comparing this to the TOML parser example, as it looks fairly similar, but I don't seem to figure out whats different..

[andersfylling]

I had not added a rule for : =D

Adding {"Punct", `\[|]|[-!()+/*=:,]`} resolves it!