Unclear error message when calling non-existent function due to case-sensitive typo

[datasc31]

Background
When using the online WPL editor, calling a function with a case-sensitive typo (for example, json_unEscape instead of json_unescape) results in a low-level syntax error message. The error does not clearly indicate that the root cause is an unknown or mis-cased function name.

This behavior is confusing for first-time or trial users, as the error appears to be a grammar or pipeline syntax issue rather than a function resolution problem.

Steps to Reproduce

1. Open the online WPL editor.

2. Use the following rule snippet:

   json | take(log) | json_unEscape() | (
   ip: sip,
   2*_,
   time: recv_time<[, ]>,
   http/request",
   http/status,
   digit,
   chars",
   http/agent",
   _
   )

3. Click the “Parse” button.

Actual Result
The editor reports a generic syntax error:

WPL parse failed: [500] syntax error > parse error at line 4, column 18
invalid symbol
expected ,, next field, ( ... ), group '( ... )' content, group, , rule <name> { ... }, { rule ... }
Error Code: WPL_PARSE_ERROR

The error message does not indicate that json_unEscape is an invalid or unknown function name.

Expected Result
The error message should clearly indicate that the function name is invalid. Ideally, the editor should:

• Point out the exact invalid function name (json_unEscape)

• Mention that function names are case-sensitive

• Suggest the correct function name if possible, for example:

  Unknown function json_unEscape.
  Did you mean json_unescape?

Impact
Users may mistakenly assume there is a grammar or syntax problem and spend time debugging unrelated parts of the rule. This increases trial-and-error cost and negatively affects the initial learning and trial experience.

Suggested Improvement

• Distinguish unknown function names from generic syntax errors.
• When parsing fails at a function call position, validate the function name against the known function registry.
• Provide targeted error messages for unknown or mis-cased function names.
• Optionally offer “Did you mean …” suggestions using case-insensitive matching.