Error System | Joa Documentation

Joa produces structured error messages. Depending on the error and available source information, diagnostics include:

The error kind (Syntax, Type, Runtime, Name)
A plain-language description of what went wrong
A file reference with line and column numbers
A source excerpt with a ^ caret pointing at the exact position
A 💡 Hint suggesting how to fix it, when one is supplied

Error Format

❌ <Kind> Error: <message>
  --> <file>:<line>:<column>
   |
 N | <source line>
   |   ^
   |   <message repeated>

💡 Hint: <actionable fix>

Error Kinds

Kind	When it occurs
`Syntax Error`	Unrecognized character, missing brace, malformed token
`Type Error`	Wrong type for operation (e.g. string CIDR, non-numeric math)
`Runtime Error`	Division by zero, out-of-bounds index, wrong argument count
`Name Error`	Reading or assigning an undeclared variable

Examples

Missing opening brace:

if load > 90
    print("High load")

// ❌ Syntax Error: Expected '{' to start a block, but found 'print'.
//   --> monitor.jo:2:5
//    |
//  2 |     print("High load")
//    |     ^
//    |     Add a '{' here to open the block.

String used as subnet mask:

let zone = 192.168.0.0/16
let sub = zone.split("20")

// ❌ Type Error: subnet.split() requires an Integer CIDR prefix (e.g. split(28)).
//   --> config.jo:2:21
//    |
//  2 | let sub = zone.split("20")
//    |                     ^
// 💡 Hint: Remove quotes if you used a string: split(28) not split("28").

Undefined variable:

print(user_count)

// ❌ Name Error: 'user_count' is not defined.
//   --> app.jo:1:7
//    |
//  1 | print(user_count)
//    |       ^
// 💡 Hint: Declare it first: let user_count = ...

Division by zero:

let ratio = total / active

// ❌ Runtime Error: Division by zero.
//   --> calc.jo:1:17
// 💡 Hint: Ensure the divisor is not zero before dividing.