Fix silent error handling in FTP listener

[niveathika]

Summary

• Add upfront regex pattern validation in FormatMethodsHolder
• Replace log.error with BError.printStackTrace for visible errors
• Remove redundant code in FtpListener

Problem

Native side log.error() calls are not visible to users, causing the FTP listener to silently fail in various error scenarios.

Solution

Changed to create BError and call printStackTrace() which outputs Ballerina-formatted errors that are visible to users.

Fixes: ballerina-platform/ballerina-library#8655

🤖 Generated with Claude Code

Summary

This pull request improves error visibility and early configuration validation in the FTP listener so configuration and runtime problems are reported clearly to users instead of being silently lost.

Changes

• Error reporting: Replaced native-side log.error calls with Ballerina-formatted errors (FtpUtil.createError(...) and BError.printStackTrace()) across server and client native code (including FtpContentCallbackHandler, FtpListener, client helpers and related utilities) so native errors are surfaced to users in a consistent, visible format.
• Early validation: Added upfront regex validation for @ftp:FunctionConfig.fileNamePattern in FormatMethodsHolder during initialization to surface invalid patterns at startup and removed redundant runtime pattern exception handling.
• Cleanup: Removed or simplified redundant logging and error-checking paths and centralized error creation via FtpUtil to streamline error handling and reduce silent failures.
• Changelog: Added an unreleased note describing the fix for silent listener failures.

Outcome

Improves stability and debuggability of the FTP listener by surfacing configuration and runtime errors in a consistent, user-visible format and by catching invalid filename patterns earlier during initialization.

[coderabbitai]

📝 Walkthrough

Walkthrough

Validates fileNamePattern regexes at initialization and shifts many runtime logger log.error calls to use FtpUtil.createError(...).printStackTrace() or direct error.printStackTrace(), removing several inline logging statements and related try/catch logging in FTP client/server utilities.

Changes

Cohort / File(s)	Summary
Pattern Validation at Init native/src/main/java/io/ballerina/stdlib/ftp/server/FormatMethodsHolder.java	Adds FtpUtil.validateRegexPattern when registering fileNamePattern from annotations and removes the runtime try/catch around Pattern.matches, relying on initialization-time validation.
Server-side Error Handling native/src/main/java/io/ballerina/stdlib/ftp/server/FtpContentCallbackHandler.java, native/src/main/java/io/ballerina/stdlib/ftp/server/FtpListener.java	Replaces many log.error calls with FtpUtil.createError(...).printStackTrace() or error.printStackTrace() in async and sync error paths; simplifies legacy onFileChange fallback and removes some runtime parameter-type error logs.
Client-side & Utilities native/src/main/java/io/ballerina/stdlib/ftp/client/FtpClientHelper.java, native/src/main/java/io/ballerina/stdlib/ftp/client/FtpClientListener.java, native/src/main/java/io/ballerina/stdlib/ftp/util/FtpContentConverter.java, native/src/main/java/io/ballerina/stdlib/ftp/util/FtpUtil.java	Removes several log.error calls in client listeners/helpers and content converters; some exceptions now complete/return errors without logging. FtpUtil.extractPortValue no longer logs an invalid-port error (still returns -1).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related issues

• [ftp] Listener silently fails when errors occur - native log.error() calls are not visible ballerina-library#8655: Matches this PR’s objectives—early regex validation in FormatMethodsHolder and replacing log.error calls with FtpUtil.createError(...).printStackTrace() across the FTP server/client files.

Poem

🐇 I hopped through patterns, snug and tight,
I checked each regex in the night,
When errors came I let them show,
Stack traces sparkling in a row,
Hooray — the FTP burrow’s just right! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 21.43% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Merge Conflict Detection	⚠️ Warning	❌ Merge conflicts detected (8 files): ⚔️ changelog.md (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/client/FtpClientHelper.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/client/FtpClientListener.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/server/FormatMethodsHolder.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/server/FtpContentCallbackHandler.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/server/FtpListener.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/util/FtpContentConverter.java (content) ⚔️ native/src/main/java/io/ballerina/stdlib/ftp/util/FtpUtil.java (content) These conflicts must be resolved before merging into master.	Resolve conflicts locally and push changes to this branch.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Fix silent error handling in FTP listener' accurately and concisely describes the main objective of the PR.
Description check	✅ Passed	The description covers Purpose (problem and solution), includes a changelog entry, and links to the issue, meeting the core template requirements.
Linked Issues check	✅ Passed	All required changes from issue #8655 are implemented: regex pattern validation in FormatMethodsHolder, replacing log.error with BError.printStackTrace in FormatMethodsHolder, FtpContentCallbackHandler, FtpListener, FtpClientHelper, FtpClientListener, and FtpUtil.
Out of Scope Changes check	✅ Passed	All changes are directly aligned with issue #8655; changelog updates and code modifications are all within the stated objectives.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-silent-error-handling

⚔️ Resolve merge conflicts (beta)

• Auto-commit resolved conflicts to branch fix-silent-error-handling
• Create stacked PR with resolved conflicts
• Post resolved changes as copyable diffs in a comment

---

No actionable comments were generated in the recent review. 🎉

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@native/src/main/java/io/ballerina/stdlib/ftp/server/FtpListener.java`:
- Around line 171-175: The fallback branch currently calls
onFileChangeMethodType.get() which can throw if absent; update FtpListener to
first check Optional.isPresent() for the result of
getOnFileChangeMethod(service) and only call
processMetadataOnlyCallbacks(service, event, onFileChangeMethodType.get(),
caller) when present; if not present, handle defensively (e.g., log a clear
warning/error with context using the existing logger and return or skip
processing) so there is no uncaught NoSuchElementException.

[sonarqubecloud]

Quality Gate passed

Issues
0 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

[codecov]

Codecov Report

❌ Patch coverage is 12.50000% with 21 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.61%. Comparing base (4a0c824) to head (866fed5).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
...a/stdlib/ftp/server/FtpContentCallbackHandler.java	0.00%	16 Missing ⚠️
...va/io/ballerina/stdlib/ftp/server/FtpListener.java	20.00%	4 Missing ⚠️
...llerina/stdlib/ftp/server/FormatMethodsHolder.java	66.66%	0 Missing and 1 partial ⚠️

❌ Your project status has failed because the head coverage (76.61%) 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    #1549      +/-   ##
============================================
+ Coverage     76.53%   76.61%   +0.07%     
  Complexity     1043     1043              
============================================
  Files            76       76              
  Lines          4833     4823      -10     
  Branches        838      837       -1     
============================================
- Hits           3699     3695       -4     
+ Misses          760      755       -5     
+ Partials        374      373       -1     

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