Friadne: A Compiler Diagnostic Library for F#

How to Use

1. Define a Location: Specify the file and the primary range for the diagnostic.
2. Create a Diagnostic: Use Diagnostics.createError, Diagnostics.createWarning, etc.
3. Add Annotations: Use Diagnostics.withAnnotation to highlight specific code segments within the diagnostic's range and provide messages for them. Annotations can have their own severity level, influencing their color.
4. Add Notes and Help: Use Diagnostics.withNote and Diagnostics.withHelp for additional information.
5. Render or Print: Use Diagnostics.render to get the string representation or Diagnostics.print to output directly to the console.

Example:

Here's how you might define an error diagnostic with multiple annotations on a single line and a note:

open Friadne

// Assuming 'demo.fsx' is the file being analyzed
let location =
    { FileName = "demo.fsx"
      Range =
        { Start = { Line = 7; Column = 20 } // Primary range for the error
          End = { Line = 7; Column = 30 } } }

let diagnostic =
    Diagnostics.createError "FS" 0001 "Type error" location
    |> Diagnostics.withAnnotation
        { Start = { Line = 7; Column = 20 } // First annotation
          End = { Line = 7; Column = 29 } }
        "This expression was expected to have type 'a array"
        DiagnosticLevel.Info // Annotations can have their own level for styling
    |> Diagnostics.withAnnotation
        { Start = { Line = 7; Column = 30 } // Second annotation
          End = { Line = 7; Column = 30 } }
        "but here has type 'a list"
        DiagnosticLevel.Info
    |> Diagnostics.withNote "Incompatible types"

// To print to console:
// Diagnostics.print diagnostic

// To get as a string:
// let outputString = Diagnostics.render diagnostic

Running the Demo Project

To see Friadne in action with more examples, you can run the test project:

dotnet run --project Friadne.Test -- demo.fsx

LICENSE

Copyright (c) 2025 Somhairle H. Marisol

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