Add content-based build caching with ADO Cache@2

[mattleibow]

Summary

Adds content-based build caching via ADO Cache@2 and restructures the Cake build system into isolated, standalone files. Native builds skip in 1-2 minutes on cache hit. Managed builds and NuGet packaging also cache. Full dependency tracking ensures native code changes cascade to managed/package stages.

Cache Performance

Stage	Main avg	Cached	Saving
Native macOS	109.6m	3.5m	-106m (97%)
Native Windows	78.6m	1.6m	-77m (98%)
Native Linux	43.9m	8.1m	-36m (82%)
Native WASM	37.7m	7.6m	-30m (80%)
Managed (libs)	40.1m	2.0m	-38m (95%)
Package NuGets	40.7m	2.1m	-39m (95%)
Tests	81.0m	—	not cached (must execute)
Samples	~30m	—	not cached (must execute)
Total cached savings			~326 min per build

Main averages based on last 10 builds.

Cache Invalidation (verified on CI)

Scenario	Build	Native	Managed/Package
1. Ignored file (.editorconfig)	71 cached, 0 built	⚡ all hit	⚡ all hit
2. Binding file (SKPaint.cs)	65 cached, 5 built	⚡ all hit	🔨 all miss
3. Native android (build.cake)	57 cached, 14 built	⚡ 57 hit, 🔨 8 android miss	🔨 all miss (dependsOn)

How It Works

Content-based cache keys: {job}_{name}_{submodule_shas}_{file_hash}

• Each job hashes its tracked files + submodule SHAs into a unique key
• Cache@2 restores output/ on hit → skips full checkout + build
• dependsOn in config propagates: native change → managed/package/test invalidate
• Cache scoping (ADO built-in): PRs read from main, write to PR scope only

What invalidates ALL caches (root-level tracked)

These files are in the root-level include — changing any of them busts every cache key:

File	Why
scripts/VERSIONS.txt	Native lib versions, NuGet versions, assembly versions
scripts/infra/shared/**	Shared Cake constants and utilities
scripts/azure-*.yml	Pipeline logic (steps, args, conditions)
nuget.config	NuGet feed URLs affect package restore
global.json	.NET SDK version affects all builds
.config/**	Cake version, xharness, docfx tool versions
.gitmodules	Submodule URLs/branches affect checkout
.editorconfig	34 analyzer rules evaluated during dotnet build
scripts/infra/security/**	Security scan config — critical, should force full rebuild

Cache key tool (scripts/infra/caching/repo-deps.py)

# Compute key with dependency tree
python3 repo-deps.py cache-key --job managed/package --name package_normal_windows

# Show changed files with * markers
python3 repo-deps.py cache-key --job all --name prepare --base origin/main

# Validate all files covered
python3 repo-deps.py validate

Controls

• enableCaching parameter: UI checkbox in ADO "Run pipeline" (default: on)
• Enabled on public CI + hybrid-internal; disabled on official internal pipelines
• Prepare stage shows full dependency tree with * markers for changed files

Cake Build Isolation

build.cake is now a pure dispatcher — zero #addin, zero #tool, single #load:

build.cake (dispatcher)
  ├── scripts/infra/managed/libs.cake
  ├── scripts/infra/package/nuget.cake
  ├── scripts/infra/docs/docs.cake
  ├── scripts/infra/samples/samples.cake
  ├── scripts/infra/tests/tests-{netfx,netcore,android,apple,wasm}.cake
  ├── scripts/infra/managed/interop.cake
  └── scripts/infra/managed/externals-download.cake

All constants in scripts/infra/shared/shared.cake. Each domain uses ROOT_PATH for repo-relative paths. Editing one domain cannot affect another.

Scripts Restructure

scripts/infra/
  shared/     ← shared.cake, msbuild.cake, download.cake
  native/     ← per-platform native build infra
  managed/    ← managed build scripts + installers
  docs/       ← API documentation (docs.cake)
  tests/      ← per-platform test runners
  samples/    ← sample builds
  package/    ← NuGet packaging
  caching/    ← repo-deps.py + repo-deps.json
  security/   ← security scan config (root-level cache invalidation)

32 unused legacy scripts deleted (including build.ps1/build.sh — not used in CI).

Dependency Config (repo-deps.json)

{
  "native": {
    "submodules": ["externals/skia", "externals/depot_tools"],
    "children": { "android": {...}, "ios": {...}, ... }
  },
  "managed": {
    "dependsOn": ["native"],
    "children": {
      "libs": {},
      "package": { "children": { "api_diff": {...}, "samples": {...} } },
      "tests": {}
    }
  }
}

Children inherit parent paths. dependsOn accumulates all files from the referenced job tree. Tests and samples are isolated siblings — editing test files doesn't trigger sample rebuilds and vice versa.

Other Changes

• Vulkan always enabled. Direct3D toggle kept for NanoServer only
• Fixed Docker build-local.sh paths after restructure
• Removed unused #addin (Cake.Xamarin, Cake.XCode, Mono.Cecil) and #tool vswhere
• Fixed 12h→24h clock in DATE_TIME_STR to avoid AM/PM collisions
• Quoted WASM project path to handle spaces

Pre-existing Failures

Linux/Windows sample builds fail with -mretpoline (same on main).

[github-actions]

📦 Try the packages from this PR

Warning

Do not run these scripts without first reviewing the code in this PR.

Step 1 — Download the packages

bash / macOS / Linux:

curl -fsSL https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.sh | bash -s -- 3826

PowerShell / Windows:

iex "& { $(irm https://raw.githubusercontent.com/mono/SkiaSharp/main/scripts/get-skiasharp-pr.ps1) } 3826"

Step 2 — Add the local NuGet source

dotnet nuget add source ~/.skiasharp/hives/pr-3826/packages --name skiasharp-pr-3826

More options

Option	Description
--successful-only / -SuccessfulOnly	Only use successful builds
--force / -Force	Overwrite previously downloaded packages
--list / -List	List available artifacts without downloading
--build-id ID / -BuildId ID	Download from a specific build

Or download manually from Azure Pipelines — look for the nuget artifact on the build for this PR.

Remove the source when you're done:

dotnet nuget remove source skiasharp-pr-3826

[github-actions]

📖 Documentation Preview

The documentation for this PR has been deployed and is available at:

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🔗 View Staging SkiaFiddle

This preview will be updated automatically when you push new commits to this PR.

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[Copilot]

Pull request overview

Copilot reviewed 94 out of 147 changed files in this pull request and generated 5 comments.