Errors in Groovy

In Groovy, error handling is typically done using exceptions, similar to Java. However, we can create a structure that mimics Go’s error handling style for demonstration purposes.

import groovy.transform.CompileStatic

// By convention, we'll use a Tuple to return both a result and an error
@CompileStatic
Tuple2<Integer, String> f(int arg) {
    if (arg == 42) {
        // Return a Tuple with -1 as the result and an error message
        return new Tuple2<>(-1, "can't work with 42")
    }
    // Return a Tuple with the result and null for no error
    return new Tuple2<>(arg + 3, null)
}

// Define sentinel errors as constants
final String ERR_OUT_OF_TEA = "no more tea available"
final String ERR_POWER = "can't boil water"

@CompileStatic
String makeTea(int arg) {
    if (arg == 2) {
        return ERR_OUT_OF_TEA
    } else if (arg == 4) {
        // Wrap the error with additional context
        return "making tea: $ERR_POWER"
    }
    return null
}

// Main function
static void main(String[] args) {
    [7, 42].each { i ->
        def (result, error) = f(i)
        if (error) {
            println "f failed: $error"
        } else {
            println "f worked: $result"
        }
    }

    (0..4).each { i ->
        def err = makeTea(i)
        if (err) {
            // In Groovy, we use switch for pattern matching
            switch (err) {
                case ERR_OUT_OF_TEA:
                    println "We should buy new tea!"
                    break
                case { it.contains(ERR_POWER) }:
                    println "Now it is dark."
                    break
                default:
                    println "unknown error: $err"
            }
        } else {
            println "Tea is ready!"
        }
    }
}

In this Groovy version:

We use Tuple2 to mimic Go’s multiple return values for the f function.
Instead of using a separate error type, we use String for error messages.
The makeTea function returns String for errors and null for success, similar to Go’s approach.
We use Groovy’s switch statement with pattern matching to check for specific error conditions, which is similar to Go’s errors.Is functionality.
The @CompileStatic annotation is used to enable static type checking, making the code more similar to statically-typed languages like Go.
Groovy’s closure syntax is used for iteration, which is similar to Go’s range-based for loops.

This code demonstrates error handling patterns in Groovy that are conceptually similar to Go’s approach, while using Groovy’s native features and idioms.

Range Over Iterators in Groovy

Custom Errors in Groovy

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Errors in Groovy