CAMEL-22841: camel-core - Add concat function to simple language

[davsclaus]

Description

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[Croway]

Code Review

Summary

This PR adds a concat() function to the Simple language for concatenating expressions with an optional separator. The implementation is solid with good test coverage.

Issues Found

1. Typo in error message - missing closing brace

File: SimpleFunctionExpression.java (lines 244 and 281)

"Valid syntax: ${concat(exp)} or ${concat(exp,exp) or ${concat(exp,exp,separator)} was: "
//                                              ^ missing closing brace

Should be: ${concat(exp,exp)} (with the closing })

2. Confusing parameter naming: right and left are semantically backwards

Files: CSimpleHelper.java:153, SimpleExpressionBuilder.java:193

The parameters are named right and left, but right appears first in the output:

public static String concat(Exchange exchange, Object right, Object left, Object separator) {
    // ...
    return val1 + (sep != null ? sep : "") + val2;  // right comes first, left comes second
}

This is counterintuitive - typically left would be the first operand. Consider renaming to first/second or exp1/exp2.

3. Inconsistent use of before vs beforeLast

File: SimpleFunctionExpression.java

• Line 241 (Simple parser): StringHelper.before(remainder, ")")
• Line 279 (CSimple code gen): StringHelper.beforeLast(remainder, ")")

This could cause different parsing behavior with nested parentheses. Is this intentional?

Verdict

The implementation works well and has good test coverage. The error message typo should be fixed. The parameter naming is a readability concern but not a blocker.

[davsclaus]

Thanks for the review