Fix data mapping function detection to exclude regular and natural expression functions in data_mappings.bal

[Copilot]

Fix: Functions in data_mappings.bal incorrectly marked as data mapping functions

• Understand the issue - Functions in data_mappings.bal are incorrectly marked as data mapping functions
• Review the current implementation in FunctionSearchCommand.java line 207
• Modify FunctionSearchCommand.java to check if the function is an expression-bodied function (not a natural expression function) before marking it as a data mapping function
• Add dataMappingsDoc parameter to FunctionSearchCommand constructor
• Update SearchCommand.from() to accept and pass dataMappingsDoc
• Update FlowModelGeneratorService to pass dataMappingsDoc when creating search command
• Add isDataMappingFunction helper method to CommonUtils
• Create test case with custom functions in data_mappings.bal
• Handle natural expression functions in data_mappings.bal (skip them entirely)
• Add test for NP function in data_mappings.bal
• Verify all cases are covered
• Fix checkstyle line length error

Summary

Fixed the issue where all functions in data_mappings.bal were incorrectly marked as data mapping functions. The fix ensures that only expression-bodied functions (excluding natural expression functions) are marked as data mapping functions.

All Cases Covered:

1. ✅ Expression-bodied functions in data_mappings.bal (like transform, mapPersonToEmployee) → isDataMappedFunction: true
2. ✅ Regular functions with block body in data_mappings.bal (like customHelper) → isDataMappedFunction: false
3. ✅ Isolated functions in data_mappings.bal (like validateAge) → isDataMappedFunction: false
4. ✅ Natural expression functions in data_mappings.bal (like generateGreeting) → Skipped entirely (not shown in results)
5. ✅ Natural expression functions in functions.bal → Skipped entirely (existing behavior maintained)

Changes Made:

1. CommonUtils.java: Added isDataMappingFunction() helper method (fixed checkstyle line length)
2. FunctionSearchCommand.java: Updated detection logic to use proper checks + skip NP functions from data_mappings.bal
3. SearchCommand.java: Added overloaded from() method for backward compatibility
4. FlowModelGeneratorService.java: Pass data_mappings.bal document to search command
5. Test case: Created custom_func_proj with all function types including NP function

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Functions created within data-mappings.bal are marked as data mapping functions</issue_title>
<issue_description>### Description

Data mapper supports creating mappings using custom functions and those functions are created within the data-mappings.bal file. However those functions are marked as "isDataMappedFunction": true, in the response of flowDesignService/search

Steps to Reproduce

Create a mpping with a custom function and try to add a new data mapper invocation. The custom functions will also apear as data mapping functions.

Version

v0.9.6

Environment Details (with versions)

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

@dulajdilshan The reason for this is - In the LS, we check only whether a particular function is in within the `data_mapping.bal`. Check this line: https://github.com/ballerina-platform/ballerina-language-server/blob/632c9f910db19905586c76c76e52421eb5d0c282/flow-model-generator/modules/flow-model-generator-core/src/main/java/io/ballerina/flowmodelgenerator/core/search/FunctionSearchCommand.java#L207

We need to fix this.

@madushajg @pasindufernando1 What if a pro-code user has defined functions directly inside data-mappings.bal? In that case, those functions shouldn’t appear as data mapping functions in the visualizer. @dulajdilshan > [@pasindufernando1](https://github.com/pasindufernando1) What if a pro-code user has defined functions directly inside data-mappings.bal? In that case, those functions shouldn’t appear as data mapping functions in the visualizer.

@pasindufernando1 We can fix this with the solution I posted above.</comment_new>
<comment_new>@dulajdilshan
@pasindufernando1 Why can't we use a similar approach we used in natural-expression here?

https://github.com/ballerina-platform/ballerina-language-server/blob/85eda1f19d8cc963cdffac60c5d1926a51b1b11a/langserver-core/src/main/java/org/ballerinalang/langserver/version/BallerinaU130CompilerApi.java ?

And done in here too https://github.com/dulajdilshan/ballerina-language-server/blob/2401e46936de947e276d1c50ea0cdce42e94ee07/architecture-model-generator/modules/architecture-model-generator-core/src/main/java/io/ballerina/artifactsgenerator/ModuleNodeTransformer.java#L91

Fixes wso2/product-ballerina-integrator#26

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[dulajdilshan]

@copilot Have we covered all the cases in the issue?

[Copilot]

@copilot Have we covered all the cases in the issue?

Yes, all cases are now covered. The fix handles:

1. Expression-bodied functions → marked as data mapping functions
2. Regular functions with block bodies → NOT marked as data mapping
3. Isolated functions → NOT marked as data mapping
4. Natural expression (NP) functions → skipped entirely (not shown in results)

Added an additional check (commit f7ec891) to skip NP functions from data_mappings.bal, ensuring consistent behavior with NP functions in functions.bal. The test case now includes a natural expression function to validate this scenario.

[dulajdilshan]

Created #382, since it is not allowed to merge changes from authors without signed contributors license agreement.