feat: Add CEL-based conditional function execution (#4388)

Author: SurbhiAgarwal1

.agent/QUICK_PR_COMMANDS.md

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+# Quick PR Creation Guide
+
+## Run these commands in order:
+
+# 1. Create branch
+git checkout -b feat/cel-conditional-execution
+
+# 2. Add all changes
+git add .
+
+# 3. Commit with descriptive message
+git commit -m "feat: Add CEL-based conditional function execution
+
+Implements #4388
+
+- Add 'condition' field to Function schema for CEL expressions
+- Integrate google/cel-go library for condition evaluation  
+- Skip function execution when condition evaluates to false
+- Add comprehensive unit and E2E tests
+
+Functions can now be conditionally executed based on package contents:
+
+pipeline:
+  mutators:
+  - image: set-namespace:v0.4
+    condition: \"resources.exists(r, r.kind == 'ConfigMap')\"
+"
+
+# 4. Push to your fork
+git push origin feat/cel-conditional-execution
+
+# 5. Go to GitHub and create PR!
+# https://github.com/kptdev/kpt/compare/main...YOUR_USERNAME:feat/cel-conditional-execution

.agent/github_comment_4382.md

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+# Comment to Post on Issue #4382
+
+Post this on: https://github.com/kptdev/kpt/issues/4382
+
+---
+
+Hi @liamfallon! I'd like to work on this issue.
+
+I've reviewed PR #4355 (the code transfer) and explored both the `kpt` and Porch repositories. Before I start moving documentation, I need clarification on which specific documentation should be transferred from Porch to kpt:
+
+**Questions:**
+
+1. **Which documentation files/sections** should be moved? The current Porch docs at https://docs.porch.nephio.org/ seem to be Porch-specific (e.g., API server, repositories, packages). Are there specific sections that are actually kpt-related?
+
+2. **What should I look for?** Should I focus on:
+   - API documentation that was updated in Porch?
+   - User guides that apply to kpt functionality?
+   - Function documentation?
+   - Something else?
+
+3. **Where is the source?** Should I look at:
+   - The Porch documentation source in `nephio-project/porch/docs/`?
+   - Or another location?
+
+I'm ready to help, but I want to make sure I'm moving the right content! Could you point me to the specific files or sections I should focus on?
+
+Thanks!

.agent/github_comment_4388.md

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+Hey! I'd like to take this one if it's still available.
+
+I've been looking through the issue and the codebase, and this seems like a really useful feature. The workaround of writing a custom function just to check a condition is definitely awkward when you just want to do something simple like set-annotation.
+
+Here's what I'm thinking for the implementation:
+
+**Approach:**
+- Add a `condition` field to the Function struct in the pipeline schema
+- Use the CEL library (google/cel-go) for evaluating expressions
+- The runner will check the condition before executing each function
+- If condition evaluates to false, skip the function (just pass through the input unchanged)
+
+**Example of what it would look like:**
+```yaml
+pipeline:
+  mutators:
+  - image: gcr.io/kpt-fn/set-namespace:v0.4
+    condition: "resources.exists(r, r.kind == 'ConfigMap' && r.metadata.name == 'env-config')"
+    configMap:
+      namespace: production
+```
+
+I'll start with the schema changes and get CEL integrated into the runner. Should have something working soon.
+
+Let me know if there are any specific considerations I should keep in mind!

.agent/issue_4382_action_plan.md

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+# Action Plan: Issue #4382 - Move kpt docs from Porch to kpt
+
+**🔗 Link**: https://github.com/kptdev/kpt/issues/4382  
+**👤 Created by**: @liamfallon (Core Maintainer)  
+**📅 Created**: Feb 10, 2026  
+**🏷️ Labels**: `documentation`, `good first issue`, `cleanup`  
+**⏱️ Estimated Time**: 4-8 hours
+
+---
+
+## 📋 **What This Issue Is About**
+
+**Background**:
+- Porch (Package Orchestration service) was originally part of kpt
+- Porch was donated to the Nephio project (now at `nephio-project/porch`)
+- During the split, kpt code was duplicated in Porch
+- Porch team rewrote documentation for their cloned kpt code
+- Now that code is being ported BACK to kpt (#4355 completed this)
+- **We need to also move the NEW kpt-related documentation from Porch back to kpt**
+
+**Your Task**:
+Move the improved kpt-related documentation from `nephio-project/porch` repository to `kptdev/kpt` repository
+
+---
+
+## 🎯 **Step-by-Step Plan**
+
+### **Phase 1: Research & Understand** (1-2 hours)
+
+#### Step 1: Comment on the Issue to Claim It
+```markdown
+Hi @liamfallon! I'd like to work on this issue.
+
+Before I start, could you clarify:
+1. Which specific documentation files/sections from Porch should be moved to kpt?
+2. Should I look in the Nephio porch repo (nephio-project/porch) or is there another location?
+3. Are there any specific paths or folders I should focus on?
+
+I'm ready to help move the kpt-related docs over!
+```
+
+**Why**: Get clarification from the maintainer before starting work
+
+#### Step 2: Explore the Porch Repository
+- **Repo**: https://github.com/nephio-project/porch
+- **Look for**: Documentation related to kpt (not Porch-specific features)
+- **Check directories**:
+  - `/docs/`
+  - `/documentation/`
+  - `/README.md`
+  - Any `/api/` or `/guides/` folders
+
+#### Step 3: Explore the kpt Repository Documentation
+- **Current docs location**: `c:\Users\Surbhi\Catroid\kpt\documentation\`
+- **Understand structure**:
+  - How docs are organized
+  - Naming conventions
+  - Link patterns
+
+#### Step 4: Identify What to Move
+Create a list of:
+- Documentation files about kpt features (not Porch-specific)
+- Updated API docs
+- Improved guides/tutorials
+- Any new examples
+
+---
+
+### **Phase 2: Move Documentation** (2-4 hours)
+
+#### Step 5: Create a New Branch
+```bash
+cd c:\Users\Surbhi\Catroid\kpt
+git checkout main
+git pull origin main
+git checkout -b docs/move-from-porch
+```
+
+#### Step 6: Copy Documentation Files
+For each identified file:
+1. Download from Porch repo
+2. Place in appropriate location in kpt repo
+3. Update frontmatter/metadata if needed
+4. Update internal links to match kpt structure
+
+#### Step 7: Update Links and References
+- Fix any internal documentation links
+- Update references to reflect kpt (not Porch)
+- Ensure images/assets are included
+- Check for broken links
+
+#### Step 8: Test the Documentation Locally
+```bash
+# Navigate to documentation directory
+cd documentation
+
+# Install dependencies (if haven't already)
+npm install
+
+# Run local docs server
+npm run start
+```
+
+**Verify**:
+- All pages load correctly
+- Links work
+- Images/assets display
+- No broken references
+
+---
+
+### **Phase 3: Clean Up & Submit** (1-2 hours)
+
+#### Step 9: Write Clear Commit Messages
+```bash
+git add .
+git commit -m "docs: move kpt-related documentation from Porch
+
+Moved the following kpt-related documentation from nephio-project/porch:
+- [List specific files/sections]
+
+This documentation was rewritten in Porch and is now being moved
+back to kpt following the code port in #4355.
+
+Fixes #4382
+```
+
+#### Step 10: Create Pull Request
+```bash
+git push origin docs/move-from-porch
+```
+
+**PR Title**: `docs: Move kpt-related documentation from Porch`
+
+**PR Description Template**:
+```markdown
+## Description
+
+This PR moves kpt-related documentation from the Porch repository 
+(nephio-project/porch) back to kpt, following the code port completed in #4355.
+
+## Changes
+
+### Documentation Moved:
+- [ ] [File 1] - Brief description
+- [ ] [File 2] - Brief description
+- [ ] [etc.]
+
+### Updates Made:
+- [ ] Fixed internal links to match kpt structure
+- [ ] Updated references from Porch to kpt
+- [ ] Verified all images/assets are included
+- [ ] Tested documentation builds locally
+
+## Testing
+
+- [x] Documentation builds without errors
+- [x] All links work correctly
+- [x] Images/assets display properly
+- [x] Verified on local dev server
+
+## Related Issues
+
+Fixes #4382
+Part of #4378
+
+## Screenshots (if applicable)
+
+[Add screenshots of doc pages if helpful]
+
+## Checklist
+
+- [ ] Documentation builds successfully
+- [ ] All links verified
+- [ ] No broken images
+- [ ] Commit messages follow conventions
+- [ ] PR description is clear
+```
+
+#### Step 11: Address Review Feedback
+- Respond promptly to maintainer comments
+- Make requested changes
+- Re-test after updates
+
+---
+
+## 📚 **Resources You'll Need**
+
+### Repositories:
+- **Porch (Nephio)**: https://github.com/nephio-project/porch
+- **kpt**: https://github.com/kptdev/kpt (you already have this)
+
+### Related Issues:
+- **#4378** (EPIC): https://github.com/kptdev/kpt/issues/4378
+- **#4355** (Code port PR): https://github.com/kptdev/kpt/pull/4355
+
+### kpt Documentation:
+- **Live site**: https://kpt.dev
+- **Local path**: `c:\Users\Surbhi\Catroid\kpt\documentation\`
+
+---
+
+## ⚠️ **Potential Challenges**
+
+1. **Unclear which docs to move**
+   - **Solution**: Ask maintainer for specific guidance in issue comment
+
+2. **Documentation structure differences**
+   - **Solution**: Study kpt docs structure first, adapt Porch docs to match
+
+3. **Broken links after moving**
+   - **Solution**: Use VSCode search to find/replace link patterns
+
+4. **Build errors**
+   - **Solution**: Test locally before submitting PR
+
+---
+
+## ✅ **Success Criteria**
+
+- [ ] Identified all kpt-related docs from Porch
+- [ ] Moved docs to appropriate locations in kpt
+- [ ] All links work correctly
+- [ ] Documentation builds without errors
+- [ ] Images/assets included and working
+- [ ] Clear commit messages
+- [ ] PR approved and merged
+
+---
+
+## 🚀 **Ready to Start!**
+
+### First Action: Post Comment on Issue
+
+Copy this comment and post it on https://github.com/kptdev/kpt/issues/4382:
+
+```
+Hi @liamfallon! I'd like to work on this issue.
+
+Before I start, could you clarify:
+1. Which specific documentation files/sections from Porch should be moved to kpt?
+2. Should I look in the Nephio porch repo (nephio-project/porch) or is there another location?
+3. Are there any specific paths or folders I should focus on?
+
+I'm ready to help move the kpt-related docs over! I'll start by exploring both repositories to identify candidates, but your guidance would help ensure I'm moving the right content.
+
+Thanks!
+```
+
+---
+
+**After posting the comment, while waiting for response**:
+1. Explore https://github.com/nephio-project/porch/tree/main/docs
+2. Compare with `c:\Users\Surbhi\Catroid\kpt\documentation\`
+3. Create a draft list of candidate files to move
+
+**Next Steps Document**: Once you get clarity, we'll create a detailed file-by-file migration plan!