TSServer navtree — Way to differentiate function declarations from function expressions

TypeScript Version: 3.3.0-dev.20181214

Search Terms:

• tsserver
• navtree

Problem
For https://github.com/Microsoft/vscode/issues/22981, we'd like a way to differentiate function delcarations from function expressions. Consider a file:

function foo(f) { }

foo(function bar() { })

const car = function dar(f) { }

VS Code uses the navtree to get possible code lens locations. We would only like to show references code lenses on function foo and perhaps on const car =, not on the expression foo(function bar() {}).

Using the navtree request against the TS Server, we cannot tell function declarations like foo from function expressions like bar :

 {
            "text": "bar",
            "kind": "function",
            "kindModifiers": "",
            "spans": [
                {
                    "start": {
                        "line": 3,
                        "offset": 5
                    },
                    "end": {
                        "line": 3,
                        "offset": 23
                    }
                }
            ],
            "nameSpan": {
                "start": {
                    "line": 3,
                    "offset": 14
                },
                "end": {
                    "line": 3,
                    "offset": 17
                }
            }
        },
        {
            "text": "dar",
            "kind": "function",
            "kindModifiers": "",
            "spans": [
                {
                    "start": {
                        "line": 5,
                        "offset": 13
                    },
                    "end": {
                        "line": 5,
                        "offset": 32
                    }
                }
            ],
            "nameSpan": {
                "start": {
                    "line": 5,
                    "offset": 22
                },
                "end": {
                    "line": 5,
                    "offset": 25
                }
            }
        },
        {
            "text": "foo",
            "kind": "function",
            "kindModifiers": "",
            "spans": [
                {
                    "start": {
                        "line": 1,
                        "offset": 1
                    },
                    "end": {
                        "line": 1,
                        "offset": 20
                    }
                }
            ],
            "nameSpan": {
                "start": {
                    "line": 1,
                    "offset": 10
                },
                "end": {
                    "line": 1,
                    "offset": 13
                }
            }
        }
    ]

Proposal
Differentiate:

function foo(f) { }

by using a kindModifier of "definition" or a similar name (or do the inverse and mark function bar() { } with a kindModifier of "expression")

Also, we correctly differentiate car using "kind": "const" in the case of:

const car = function(f) { }

However only dar is returned for for:

const car = function dar(f) { }

Start by tracing the tsserver navtree request and its response construction, using the reported function declaration and function expression examples as the expected behavior. Determine where kind and kindModifiers are assigned, then verify that the response distinguishes declarations from expressions, including named functions assigned to const variables.