feat: improve pipeline log extraction for catchError and parallel failures

[lidiams96]

Problem

The current PipelineLogExtractor has two limitations that cause it to miss real errors in production pipelines:

1. Single-match Strategy 1: The FlowGraph walk returns on the first ErrorAction+LogAction node found. In pipelines with parallel failures (e.g. multiple test runner pods crashing simultaneously), only the first error is captured and subsequent failures are dropped.

2. catchError + sh(returnStatus:true) + error() pattern not detected: This common pipeline pattern is invisible to Strategy 1. sh(returnStatus:true) does not throw so it has no ErrorAction. The subsequent error() step records an ErrorAction but has no LogAction (it only carries the message string, not the sh output). Strategy 1 finds the error() node, skips it (no LogAction), and falls back to run.getLog(maxLines) — which returns the last N lines of the full console log and misses the actual error output when the build has many subsequent steps.

Solution

Strategy 1 — multi-collect: Instead of returning on the first ErrorAction+LogAction match, accumulate logs from all matching nodes up to maxLines, using a HashSet to deduplicate by origin node ID (reverse-chronological walk may visit the same origin via multiple FlowGraph paths).

Strategy 2 (new) — WarningAction walk: Runs only when Strategy 1 finds nothing. Walks the FlowGraph looking for step nodes with a LogAction enclosed by a BlockStartNode carrying a WarningAction worse than SUCCESS. This handles pipeline variants where catchError records a WarningAction on the block's start node rather than an ErrorAction on the failing step. Requires ≥ 2 lines matching the error pattern to avoid capturing CI infrastructure steps (e.g. a curl command whose JSON payload happens to contain "failed") ahead of the actual failing step log.

Strategy 3 — always-on supplement: The error pattern scan previously ran only as a final fallback when all other strategies produced nothing. It now always runs after Strategies 1 and 2, filling the remaining maxLines budget with lines from the full console log that match error keywords (error, exception, failed, fatal) plus ±5 lines of surrounding context. Lines already captured by Strategies 1 or 2 are skipped via HashSet deduplication. This reliably surfaces the catchError+sh(returnStatus:true)+error() pattern and catches errors buried early in large build logs.

Alternatives

• Keeping Strategy 3 as fallback only: The existing approach worked for simple pipelines but missed the catchError+error() case where Strategy 1 finds an ErrorAction node with no usable log. The supplement approach avoids redundant I/O when Strategies 1/2 already filled the budget and adds no overhead when Strategy 3 has nothing new to contribute.

Additional Context

Validated against a real production Jenkins pipeline (complex parallel build with thousands of tests across multiple parallel groups, ~30,000 line build log):

• Before: the plugin fell back to the last N lines and surfaced unrelated warnings instead of the actual failing step
• After: the plugin correctly surfaces the error from inside the catchError block

The 5 new integration tests in PipelineLogExtractorTest cover all three strategies and include an end-to-end test that verifies the AI provider receives the inner catchError content rather than the generic fallback log.

[Copilot]

Pull request overview

Improves PipelineLogExtractor so the plugin captures more accurate failure logs in complex pipelines (parallel failures and catchError + sh(returnStatus:true) + error() patterns), reducing reliance on the last-N-lines fallback and better surfacing real error output for AI analysis.

Changes:

• Update pipeline FlowGraph extraction to collect logs from multiple failing nodes and add a WarningAction-based walk.
• Add an always-on console-log error-pattern supplement to fill remaining maxLines.
• Add new Jenkins integration tests covering key extraction scenarios and an end-to-end verification via TestProvider.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

File	Description
src/main/java/io/jenkins/plugins/explain_error/PipelineLogExtractor.java	Implements multi-strategy log extraction (multi-collect, WarningAction walk, pattern-scan supplement) and deduping.
src/test/java/io/jenkins/plugins/explain_error/PipelineLogExtractorTest.java	Adds integration + end-to-end tests validating improved extraction behavior in realistic Pipeline scenarios.