[jira] [Assigned] (CAMEL-24703) camel-core-languages - simple: error messages should say what to write (audit against typical mistakes)

["Claus Ibsen (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CAMEL-24703?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Claus Ibsen reassigned CAMEL-24703:
-----------------------------------

    Fix Version/s: 4.23.0
         Assignee: Claus Ibsen

> camel-core-languages - simple: error messages should say what to write (audit against typical mistakes)
> -------------------------------------------------------------------------------------------------------
>
>                 Key: CAMEL-24703
>                 URL: https://issues.apache.org/jira/browse/CAMEL-24703
>             Project: Camel
>          Issue Type: Improvement
>          Components: camel-core
>            Reporter: Claus Ibsen
>            Assignee: Claus Ibsen
>            Priority: Major
>             Fix For: 4.23.0
>
>
> Every error message the Simple parser can produce was listed (about 60 throw sites in core/camel-core-languages) and checked against 50 expressions a local model typically writes in the AI authoring benchmark (2026-09-12). A model recovers from a message that says what to write and loops on one that only says what was wrong. The rendered form (message, "at location N", the expression and the * marker) is good; the texts should name the fix. The main cases:
> || model writes || today || proposed ||
> | body == 'Hello World' | Unexpected token b at location 0 | Unexpected token 'b': text outside ${...} is a literal, functions are written as ${body}, ${header.name}. Did you mean ${body} == 'Hello World'? |
> | ${body == 'x'} | Valid syntax: ${body.OGNL} was: body == 'x' | Operators go outside the function: ${body} == 'x' |
> | ${body} == x | Binary operator == does not support token null | Binary operator == needs a value on the right hand side: a quoted literal 'x', a number, true, false, null, or a function ${...}; was: x (never print "token null") |
> | ${body} = 'x' | Unexpected token = | Unknown operator '=': did you mean '=='? Operators: ==, =~, !=, <, <=, >, >=, contains, !contains, ~~, regex, in, !in, is, !is, range, !range, startsWith, endsWith |
> | ${body} == 'x' and ${header.y} == 1 | Unexpected token a | Unknown operator 'and': use && for and, \|\| for or |
> | ${body} == 'x' \|\| | Logical operator \|\| does not support token null | Logical operator \|\| needs a predicate on the right hand side |
> | ${body} == 'it''s' | expected symbol whiteSpace but was singleQuote | A literal that contains a single quote must use double quotes: "it's" |
> | ${header.foo | expected symbol functionEnd but was eol | Missing } to close ${header.foo |
> | ${padding(3)} | Unknown function: padding(3) | Unknown function 'padding': did you mean pad(3)? (closest known name; the functions are listed on the simple language functions page) |
> | ${upper(${body})} | Unknown function: upper(${body}) | as above, plus: a nested ${...} inside a function argument is not supported |
> | ${property.foo} | Unknown function: property.foo | Unknown function 'property': it is exchangeProperty.foo since Camel 3 (alias table for the Camel 2 names) |
> | ${ body }, ${Body} | Unknown function:  body  / Body | remove the spaces / functions are lower camel case: ${body} |
> | ${jsonpath($.name)} without the jar | No language could be found for: jsonpath | add camel-jsonpath to the classpath (org.apache.camel:camel-jsonpath) |
> | ${body.length() > 3} | runtime: Failed to invoke method: length() > 3 on null due to: Method should end with parenthesis | Operators go outside the function: ${body.length()} > 3 |
> | ${body.lenght()} | runtime: Failed to invoke method: lenght() on null due to: MethodNotFoundException ... on bean: hello | drop the wrong "on null"; Method lenght() not found on java.lang.String; did you mean length()? |
> | ${body.toUpperCase} | runtime: Failed to invoke method: toUpperCase on null due to: CamelExecutionException: Exception occurred during execution | No method or property toUpperCase on java.lang.String; a method call needs (): ${body.toUpperCase()} |
> Accepted silently but not what was meant, where the eval tool and validator can add a note: ${header.count} + 1 (Simple has no arithmetic, the + 1 is text), ${body} ? 'a' : 'b' (no ? : operator; the elvis operator is ?: and a conditional is iif(...)).
> Implementation notes: the parse time messages come from SimpleParserException in BaseSimpleParser, SimplePredicateParser, SimpleExpressionParser, the ast nodes and the function factories; "token null" has one origin per parser (does not support token / has no left or right hand side token); the known function names for suggestions are the BUILT_INS and EXPRESSION_ENTRIES in SimpleFunctionDispatcher plus the fixed set; the catalog validator, camel validate yaml, the TUI and the MCP tools all print these messages, so every consumer benefits. The full audit with the probe program (SimpleProbe.java, 50 cases) is kept with the benchmark material.



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