Feature Request: Add an option to require type annotations #3447

Desire

I would like a way for lua-language-server to apply a "strict" mode to the functions and tables variables of lua files. e.g. if a function takes at least one parameter or has at least one return <foo> statement, it would error if that function doesn't also have a ---@param / ---@return statement to match it.

Issue

There seems to be some arguments that can make lua-language-server more strict, for example these:

.luarc.json

{
    "diagnostics": {
        "neededFileStatus": {
            "incomplete-signature-doc": "Any",
            "missing-global-doc": "Any",
            "missing-local-export-doc": "Any"
        },
        "severity": {
            "incomplete-signature-doc": "Error",
            "missing-global-doc": "Error",
            "missing-local-export-doc": "Error"
        }
    },
}

But they seem to activate only on inlined functions or functions that have incomplete documentation. So if a function has no docs at all, it gets skipped.

Suggestion

A new diagnostic that maybe can be a warning but can be escalated to an error. And it basically says

• If it is a global variable table, it needs a ---@type
• If it is a function
  • And it has at least one parameter
    • Each parameter must define ---@param with a name + type
  • And it has at least one non-bare-return `return
    • Each parameter must define ---@return with type
• If the type annotation is a table
  • Require that the table is "filled out" with concrete types. e.g. ---@type table -> ---@type table<string, integer>

Something along these lines