crossplane-diff

crossplane-diff

A standalone tool for visualizing the differences between Crossplane resources in YAML files and their resulting state when applied to a live Kubernetes cluster. Similar to kubectl diff but with specific enhancements for Crossplane resources, particularly Composite Resources (XRs) and their composed resources.

Overview

The crossplane-diff tool helps you:

• Preview changes before applying Crossplane resources to a cluster
• Visualize differences at multiple levels: both the XR itself and all downstream composed resources
• Support complex compositions including functions, requirements, and environment configurations
• Handle both Crossplane v1 and v2 resource definitions, including namespaced composite resources
• Detect resources that would be removed by your changes

Installation

Download Pre-built Binary

Download the latest release from the releases page.

Build from Source

git clone https://github.com/crossplane-contrib/crossplane-diff.git
cd crossplane-diff
go build -o crossplane-diff ./cmd/diff

Usage

Basic Usage

# Show changes that would result from applying an XR from a file
crossplane-diff diff xr.yaml

# Show changes from stdin
cat xr.yaml | crossplane-diff diff -

# Process multiple files
crossplane-diff diff xr1.yaml xr2.yaml xr3.yaml

# Show changes in a compact format with minimal context
crossplane-diff diff --compact xr.yaml

# Disable color output
crossplane-diff diff --no-color xr.yaml

Command Options

crossplane-diff diff [<files> ...] [flags]

Arguments:
  [<files> ...]    YAML files containing Crossplane resources to diff.

Flags:
  --no-color      Disable colorized output.
  --compact       Show compact diffs with minimal context.
  --timeout=1m    How long to run before timing out.
  --qps=0         Maximum QPS to the API server.
  --burst=0       Maximum burst for throttle.
  --verbose       Print verbose logging statements.

Prerequisites

• A running Kubernetes cluster with Crossplane installed
• kubectl configured to access your cluster
• Appropriate RBAC permissions (see Required Permissions)

How It Works

The tool performs the following steps:

1. Load resources from YAML files or stdin
2. Find matching compositions for each Composite Resource
3. Render resources using the same composition pipeline as Crossplane
4. Resolve requirements iteratively (environment configs, external resources)
5. Propagate namespaces from XRs to managed resources (for Crossplane v2)
6. Validate resources against their schemas and enforce scope constraints
7. Calculate diffs by comparing rendered resources against current cluster state
8. Display formatted output showing what would change

Crossplane v2 Support

This tool fully supports both Crossplane v1 and v2, including:

• Cluster-scoped XRDs: Traditional cluster-wide resources
• Namespaced XRDs: Resources confined to specific namespaces for better isolation
• Automatic scope detection: Determines whether XRDs are cluster or namespace scoped
• Namespace propagation: Ensures managed resources inherit appropriate namespaces
• Scope validation: Enforces rules like "namespaced XRs cannot own cluster-scoped managed resources"

Note: Namespace information is read directly from the XR definitions in your YAML files, not from command-line flags.

Required Permissions

The tool requires read access to:

• Crossplane definitions: XRDs, Compositions, Functions
• Crossplane runtime resources: XRs, Claims, Managed Resources
• Crossplane configuration: EnvironmentConfigs
• Kubernetes resources: CRDs, referenced resources
• Resource hierarchies: Owner references and relationships

Output Format

The output follows familiar diff conventions with colorized output (unless disabled):

+++ Resource/new-resource-(generated)
+ apiVersion: nop.crossplane.io/v1alpha1
+ kind: NopResource
+ metadata:
+   name: new-resource
+ spec:
+   forProvider:
+     field: value

---
--- XNopResource/removed-resource
- apiVersion: diff.example.org/v1alpha1
- kind: XNopResource
- spec:
-   coolField: goodbye!

~~~
~~~ Resource/modified-resource
  metadata:
    name: modified-resource
- spec:
-   oldValue: something
+ spec:
+   newValue: something-else
---

Summary: 1 added, 1 modified, 1 removed

Guiding Principles

The tool prioritizes accuracy above all else:

• Never silently continues in the face of failures
• Avoids making best-guesses that could compromise accuracy
• Fails completely rather than emit potentially incorrect partial results
• Reaches extensively into the cluster for all information needed to produce accurate diffs
• Caches resources only to avoid API throttling

Caveats

The tool does not take a snapshot of cluster state before processing, so changes made to the cluster during execution may affect results.

Documentation

• Design Document: Comprehensive technical design and architecture
• CLAUDE.md: Instructions for Claude. Contains development principles and guidelines for LLMs.

Development

Local Development Setup

Prerequisites:

• Go 1.24+
• Docker
• Earthly (install instructions)
• kubectl

Setup Steps:

1. Install required tools:

   go install sigs.k8s.io/controller-runtime/tools/setup-envtest@release-0.20
   setup-envtest use 1.30.3 # or whatever cluster version we're using now
   

2. Generate test manifests:

   earthly +go-generate --CROSSPLANE_IMAGE_TAG=main
   

3. Build the project:

   earthly +build
   

Running Tests

Unit and Integration Tests (fast):

cd cmd/diff
go test ./...

Development Checks (linting, tests, generation):

# Run before opening any PR
earthly +reviewable

End-to-End Tests:

# Full test matrix against multiple Crossplane versions (slower)
earthly -P +e2e-matrix

# Single E2E test against specific version
earthly +e2e --CROSSPLANE_IMAGE_TAG=main

Build and Development Commands

# Build binary
earthly +build

# Run linting
earthly +lint

# Generate code/manifests
earthly +generate

# All available targets
earthly --help

Architecture

The tool follows a clean layered architecture:

• Command Layer: CLI argument parsing and coordination
• Application Layer: Process orchestration and resource loading
• Domain Layer: Core diff logic, rendering, and validation
• Client Layer: Kubernetes and Crossplane API interactions

Testing

The project includes comprehensive testing:

• Unit tests: Fast, isolated component testing
• Integration tests: Using envtest for realistic cluster interactions
• E2E tests: Full end-to-end scenarios across v1, v2-cluster, and v2-namespaced configurations

Contributing

Contributions are welcome! Please see our contributing guidelines for detailed setup instructions and development workflow.

Quick Start for Contributors:

1. Fork and clone the repository
2. Run setup: earthly +go-generate --CROSSPLANE_IMAGE_TAG=main
3. Make your changes
4. Test your changes: earthly +reviewable && earthly -P +e2e-matrix
5. Open a pull request

See CONTRIBUTING.md for complete guidelines and CODE_OF_CONDUCT.md for community standards.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.