Diagnostics.fs

/// <summary>
/// Diagnostics are information/warnings/errors that show in a problems view and usually some visial indicator like
/// a colored underline or highlight for the relevant range of the file if known.
/// </summary>
/// <remarks>This example uses pull diagnostics which is newer than the original push diagnostics.
/// You may want to support push diagnostics so that your server is compatible with older clients.</remarks>
/// <see href="https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_pullDiagnostics"/>
module LspExample.Diagnostics

open System
open Ionide.LanguageServerProtocol.Types
open LspExample.Types
open LspExample.Types.DemoLang

let private diagnostic severity range message =
    { Range = range
      Severity = Some severity
      Code = None
      CodeDescription = None
      Source = Some "demolang"
      Message = message
      Tags = None
      RelatedInformation = None
      Data = None }

let private generateDiagnosticsForLine
    { Contents = contents
      Line = line
      Value = value }
    : Diagnostic seq =
    seq {
        if contents.Length > 80 then
            diagnostic
                DiagnosticSeverity.Warning
                (range (line, 0) (line, contents.Length - 1))
                $"Line too long: {contents.Length} columns"

        if String.IsNullOrWhiteSpace contents && contents.Length > 0 then
            diagnostic
                DiagnosticSeverity.Warning
                (range (line, 0) (line, contents.Length))
                "Line is non-empty and contains whitespace"
        else
            let noLeadingSpaces = contents.TrimStart()

            if noLeadingSpaces <> contents then
                diagnostic
                    DiagnosticSeverity.Error
                    (range (line, 0) (line, contents.Length - noLeadingSpaces.Length))
                    "Line has leading whitespace"

            let noTrailingSpaces = contents.TrimEnd()

            if noTrailingSpaces <> contents then
                diagnostic
                    DiagnosticSeverity.Warning
                    (range (line, noTrailingSpaces.Length) (line, contents.Length))
                    "Line has trailing whitespace"

        match value with
        | Number number when number < 0 ->
            diagnostic
                DiagnosticSeverity.Error
                (range (line, 0) (line, contents.Length))
                "Negative numbers are not supported"
        | _ -> ()

    }

/// <summary>
/// Generate diagnostics for file contents: info, warnings, and errors
/// </summary>
/// <param name="contents">The file contents to generate diagnostics for</param>
let DocumentDiagnostics (contents: string) : Diagnostic[] =
    let documentLines = Parser.ParseFile contents

    documentLines |> Seq.collect generateDiagnosticsForLine |> Seq.toArray