Skill: Reading GitHub Actions Logs

Overview

Efficiently parse and analyze GitHub Actions logs to diagnose failures, understand build progress, and extract actionable information from the ESO Log Aggregator CI pipeline.

When to Use

• Investigating CI/CD pipeline failures
• Understanding which step in the workflow failed
• Extracting specific error messages from long logs
• Monitoring test results and build times

Commands

View Run Logs with GitHub CLI

powershell
1# View logs from a specific run (failed steps only)
2gh run view RUN_ID --log-failed
3
4# View all logs from a run (includes successful steps)
5gh run view RUN_ID --log
6
7# List recent runs to find RUN_ID
8gh run list --branch (git branch --show-current) --limit 5
9
10# Get run status
11gh run view RUN_ID

View Logs by Workflow

powershell
1# PR checks
2gh run list --workflow pr-checks.yml --limit 5
3
4# Deployment runs
5gh run list --workflow deploy.yml --limit 5
6
7# Nightly tests
8gh run list --workflow nightly-tests.yml --limit 5
9
10# Screen size tests
11gh run list --workflow screen-size-testing.yml --limit 5

View Individual Job Logs

powershell
1# List all jobs in a run
2gh run view RUN_ID --json jobs --jq '.jobs[] | "\(.id) \(.name) \(.conclusion)"'
3
4# View a specific job's logs
5gh run view RUN_ID --job JOB_ID --log

View Logs in Browser

powershell
1gh run view RUN_ID --web

🚨 Critical: Evidence-First Log Reading

NEVER guess at the problem. The purpose of reading logs is to extract the exact error — file path, line number, error code, or error message — before attempting any fix.

What counts as sufficient evidence:

Common Error Patterns

1. Formatting Failure

powershell
1gh run view RUN_ID --log-failed | Select-String "format:check|Checking formatting" -Context 5

2. Lint Errors

powershell
1# Find the error summary
2gh run view RUN_ID --log-failed | Select-String "\d+:\d+\s+error" -Context 1
3
4# Find total problem count
5gh run view RUN_ID --log-failed | Select-String "✖ \d+ problems" -Context 3

3. TypeScript Errors

powershell
1# Find TS error codes
2gh run view RUN_ID --log-failed | Select-String "error TS\d+" -Context 3
3
4# Find file paths with errors
5gh run view RUN_ID --log-failed | Select-String "\.tsx?\(\d+,\d+\): error" -Context 1

4. Test Failures

powershell
1# Find failed test suites
2gh run view RUN_ID --log-failed | Select-String "FAIL.*\.test\.(ts|tsx)" -Context 5
3
4# Get assertion errors
5gh run view RUN_ID --log-failed | Select-String "Expected:|Received:|Error:" -Context 5
6
7# Check for Node warnings BEFORE test failures (root cause)
8gh run view RUN_ID --log-failed | Select-String "\(node:\d+\) Warning" -Context 10

⚠️ Important: Test failures are often symptoms. Always look 10-20 lines BEFORE the failure for Node.js warnings or configuration errors.

5. Build Failures

powershell
1gh run view RUN_ID --log-failed | Select-String "ERROR|Error:|Module not found|Cannot find" -Context 5

6. Playwright E2E Failures

powershell
1# Server startup issues
2gh run view RUN_ID --log-failed | Select-String "server.*fail|server.*died|server.*crash" -Context 5
3
4# Test assertion failures
5gh run view RUN_ID --log-failed | Select-String "expect\(.*\)\.|playwright.*error" -Context 5

7. Skills Lint Failure

powershell
1gh run view RUN_ID --log-failed | Select-String "skill.*failed validation|✖" -Context 3

Filtering and Parsing

Save Logs to File

powershell
1# Save full logs (use scratch/ directory to avoid git pollution)
2gh run view RUN_ID --log > scratch/ci-logs.txt
3
4# Save only failed logs
5gh run view RUN_ID --log-failed > scratch/ci-failed.txt

Parse with PowerShell

powershell
1# Count occurrences of a pattern
2(gh run view RUN_ID --log | Select-String "error").Count
3
4# Extract unique error messages
5gh run view RUN_ID --log | Select-String "error TS\d+:" | Select-Object -Unique
6
7# Get files with lint errors
8gh run view RUN_ID --log | Select-String "\d+:\d+\s+error" | Select-Object -First 20

Common Troubleshooting Workflow

powershell
1# Step 1: Identify the failed run
2$runId = (gh run list --branch (git branch --show-current) --limit 1 --json databaseId --jq '.[0].databaseId')
3
4# Step 2: Get failed logs
5$logs = gh run view $runId --log-failed
6
7# Step 3: Classify the failure
8$errorTypes = @(
9  "\(node:\d+\) Warning",    # Node.js warnings (ROOT CAUSE)
10  "Cannot find module",       # Missing dependencies (ROOT CAUSE)
11  "format:check.*failed",     # Formatting
12  "error TS\d+",              # TypeScript errors
13  "\d+:\d+\s+error",          # Lint errors
14  "FAIL.*\.test\.",            # Test failures (SYMPTOM)
15  "Module not found",          # Build failures
16  "expect\(.*\)\."             # E2E failures
17)
18
19foreach ($pattern in $errorTypes) {
20  $matches = $logs | Select-String $pattern
21  if ($matches) {
22    Write-Host "Found: $pattern - Count: $($matches.Count)"
23    $matches | Select-Object -First 3 | ForEach-Object { Write-Host "  $_" }
24  }
25}

Comprehensive One-Liner Diagnostic

powershell
1$runId = (gh run list --branch (git branch --show-current) --limit 1 --json databaseId --jq '.[0].databaseId')
2$logs = gh run view $runId --log-failed
3
4@{
5  "🎨 Format"       = "format:check.*failed|Check formatting.*failed"
6  "🔍 Lint"         = "\d+:\d+\s+error.*@typescript-eslint|✖ \d+ problems"
7  "📝 TypeScript"   = "error TS\d+"
8  "🧪 Tests"        = "FAIL.*\.test\.(ts|tsx)|Test Suites:.*failed"
9  "🏗️ Build"        = "Module not found|Cannot find|BUILD FAILED"
10  "🌐 E2E"          = "playwright.*error|expect\(.*\)\.to|server.*fail"
11  "📚 Skills"       = "skill.*failed validation"
12  "⏹️ Cancelled"    = "operation was canceled|more recent commit"
13}.GetEnumerator() | ForEach-Object {
14  $hits = $logs | Select-String $_.Value
15  if ($hits) { Write-Host "$($_.Key) — $($hits.Count) hit(s)" -ForegroundColor Red }
16}

Quick Reference Table

🚨 Golden Rule: NEVER attempt a fix until you can cite the exact error from the logs. Saying "lint failed" is not enough — you need src/App.tsx:17:3 error @typescript-eslint/no-floating-promises.

💡 Pro Tip: Test failures (FAIL) are often symptoms. Always look 10-20 lines BEFORE the failure for Node.js warnings, module loading errors, or configuration issues — those are the root causes.

Related Skills

• debug-ci-failure — Full end-to-end CI debugging workflow
• fix-lint — Resolving specific ESLint rule violations
• fix-types — Fixing TypeScript type errors
• testing — Running and debugging unit tests locally
• scratch-dir — Saving log output to scratch/ directory