Introduce On error handler

[niveathika]

Purpose

Fixes ballerina-platform/ballerina-library#8605

Examples

Checklist

• Linked to an issue
• Updated the changelog
• Added tests
• Updated the spec
• Checked native-image compatibility

[Copilot]

Pull request overview

This PR introduces an onError handler for FTP services to handle content binding failures. When file content cannot be converted to the expected type (JSON, XML, CSV, or record types), a new ContentBindingError is raised. Services can define an optional onError remote function to handle these errors, enabling custom error handling such as moving failed files or logging.

Changes:

• Added ContentBindingError type with detail record containing file path and raw content bytes
• Introduced onError remote function support with validation (accepts ftp:Error or error as first parameter, optional Caller as second)
• Updated content converters to return ContentBindingError instead of generic errors, with file path context
• Added comprehensive compiler plugin validation and tests for the new error handler

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
ballerina/error.bal	Defines ContentBindingError type and detail record
ballerina/tests/listener_on_error_test.bal	Tests onError handler with various scenarios including minimal/full parameters and caller operations
ballerina/tests/client_endpoint_test.bal	Tests ContentBindingError is returned from client operations on parsing failures
native/src/main/java/io/ballerina/stdlib/ftp/util/FtpUtil.java	Adds getOnErrorMethod() and createContentBindingError() helper methods
native/src/main/java/io/ballerina/stdlib/ftp/util/FtpContentConverter.java	Updates converters to return ContentBindingError with file path and content
native/src/main/java/io/ballerina/stdlib/ftp/util/FtpConstants.java	Adds ON_ERROR_REMOTE_FUNCTION and CONTENT_BINDING_ERROR constants
native/src/main/java/io/ballerina/stdlib/ftp/server/FtpContentCallbackHandler.java	Implements onError routing when content binding fails
native/src/main/java/io/ballerina/stdlib/ftp/server/FormatMethodsHolder.java	Tracks onError method availability
native/src/main/java/io/ballerina/stdlib/ftp/client/FtpClient.java	Passes file path to content converters for error context
compiler-plugin/src/main/java/io/ballerina/stdlib/ftp/plugin/PluginConstants.java	Adds error codes and constants for onError validation
compiler-plugin/src/main/java/io/ballerina/stdlib/ftp/plugin/FtpServiceValidator.java	Integrates onError validation into service validation
compiler-plugin/src/main/java/io/ballerina/stdlib/ftp/plugin/FtpOnErrorValidator.java	Validates onError function signature and parameters
compiler-plugin-tests/*	Adds test cases for valid and invalid onError handlers
spotbugs-exclude.xml	Excludes EI_EXPOSE_REP2 for FtpOnErrorValidator

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[niveathika]

@copilot open a new pull request to apply changes based on the comments in this thread

[Copilot]

@niveathika I've opened a new pull request, #1538, to work on those changes. Once the pull request is ready, I'll request review from you.

[codecov]

Codecov Report

❌ Patch coverage is 74.21875% with 33 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.47%. Comparing base (87f197d) to head (9c1dbfe).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
...llerina/stdlib/ftp/plugin/FtpOnErrorValidator.java	67.24%	12 Missing and 7 partials ⚠️
...ain/java/io/ballerina/stdlib/ftp/util/FtpUtil.java	68.18%	3 Missing and 4 partials ⚠️
...a/stdlib/ftp/server/FtpContentCallbackHandler.java	80.00%	2 Missing and 2 partials ⚠️
...ballerina/stdlib/ftp/util/FtpContentConverter.java	81.81%	2 Missing ⚠️
...llerina/stdlib/ftp/server/FormatMethodsHolder.java	66.66%	0 Missing and 1 partial ⚠️

❌ Your project status has failed because the head coverage (78.47%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1537      +/-   ##
============================================
+ Coverage     77.89%   78.47%   +0.58%     
- Complexity      709      938     +229     
============================================
  Files            55       71      +16     
  Lines          3537     4237     +700     
  Branches        591      735     +144     
============================================
+ Hits           2755     3325     +570     
- Misses          547      604      +57     
- Partials        235      308      +73     

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[TharmiganK]

LGTM