Maui Coverage

MAUI backend coverage

Regenerate docs/maui-coverage.md — the .NET MAUI ⇄ Microsoft.AndroidX.Compose.Maui backend completeness report. The report is produced by a single .NET 10 file-based program at scripts/maui-coverage.cs that:

1. Reads the pinned Microsoft.Maui.Controls version from Directory.Build.targets.
2. Finds the matching Microsoft.Maui.dll (Core) in the local NuGet cache ($env:NUGET_PACKAGES if set, else the user-profile default).
3. Decompiles every Microsoft.Maui.Handlers.*Handler type via ilspycmd into obj/maui-coverage/maui/.
4. Regex-parses each handler's IPropertyMapper<TVirtual, THandler> field initializer — including base-mapper chains (ViewHandler.ViewMapper, sibling sub-mappers like TextButtonMapper/ImageButtonMapper).
5. Does the same for our own handlers under src/Microsoft.AndroidX.Compose.Maui/Handlers/*.cs.
6. Cross-references the two by property-mapper key name and writes a markdown report with summary, per-category roll-up, status table, gap analysis, and per-handler detail.

Workflow

1. Run the script

From the repo root (Windows / PowerShell):

dotnet run scripts/maui-coverage.cs

That's it — no .csproj, no package install, no MSBuild target. The script handles its own caching. First run shells to ilspycmd for every handler type (~40 entries, takes ~20 seconds); subsequent runs are [cached] … and finish in a couple of seconds.

Expected tail output:

Stock virtual-view registrations: 53
Report written: docs/maui-coverage.md

2. Verify the diff

git diff --stat docs/maui-coverage.md

The headline numbers live in the Summary block near the top:

Select-String -Path docs/maui-coverage.md -Pattern '^- \*\*' | Select-Object -First 5

If the totals didn't move when you expected them to (e.g. you added a new handler in src/Microsoft.AndroidX.Compose.Maui/Handlers/ but the "Handlers we override" line is unchanged), see Troubleshooting below.

3. Commit the regenerated report alongside the change that prompted it

The report is checked in deliberately so reviewers can see coverage movement in the PR diff. Don't commit the script run on its own — pair it with the handler addition, the package bump, or whatever change motivated the refresh.

git add docs/maui-coverage.md
git commit --amend --no-edit  # or a fresh commit, depending on context

Updating the MAUI version

The script reads Microsoft.Maui.Controls's version from Directory.Build.targets via regex on the <PackageReference Update="Microsoft.Maui.Controls" Version="..." /> line. When you bump MAUI:

1. Edit Directory.Build.targets to the new version (e.g. 10.0.20 → 10.0.21).
2. Run a normal dotnet build to restore the new package into the NuGet cache.
3. Wipe the decompile cache — the script keys cache files by handler type name, not by MAUI version, so stale .cs files from the previous version would be silently reused:

   Remove-Item -Recurse -Force obj/maui-coverage
   

4. Re-run the script.

Troubleshooting

"microsoft.maui.core X.Y.Z not found under ..." — the package hasn't been restored yet. Run any dotnet build in the repo first (easiest: dotnet build src/Microsoft.AndroidX.Compose.Maui). The script honours $env:NUGET_PACKAGES for non-default cache locations.

"ilspycmd: command not found" — install the global tool:

dotnet tool install -g ilspycmd

Headline % didn't move after adding a handler — there are two common causes:

• The handler isn't wired into UseAndroidXCompose() in src/Microsoft.AndroidX.Compose.Maui/Hosting/AppHostBuilderExtensions.cs. The script parses that file for handlers.AddHandler<MauiX, YHandler>() calls; an unregistered handler file under Handlers/ is invisible.
• The mapper field uses a syntax the regex doesn't recognise. The parser expects:

  public static IPropertyMapper<TVirtual, THandler> Mapper =
      new PropertyMapper<TVirtual, THandler>(ViewHandler.ViewMapper)
      {
          [nameof(IFoo.Bar)] = MapBar,
      };
  

  Variations: public new static IPropertyMapper<...> (used by PageHandler), empty { } body, and base-mapper chains across sibling sub-mappers are all handled. Custom shapes (raw Dictionary<> constructions, runtime mutation) will not be picked up — keep the declarative initializer form for consistency.

LabelHandler / CheckBoxHandler aren't listed under any virtual view — MAUI registers a handful of handlers reflectively rather than via the regex-scannable AddHandler<TVirtual, THandler>() calls in Microsoft.Maui.Controls.Hosting.AppHostBuilderExtensions. The script falls back to deriving the virtual-view name from the handler class name (XxxHandler → Xxx) for those. See SupplementWithImpliedRegistrations.

Report looks empty / 0% across the board — the decompile cache contains a half-written file. Wipe it:

Remove-Item -Recurse -Force obj/maui-coverage
dotnet run scripts/maui-coverage.cs

What the report contains

• Summary — overall percentages. Three headline numbers:

  • Stock MAUI handlers in scope — denominator for handler-level coverage (excludes the abstract ViewHandler/ElementHandler bases).
  • Handlers we override — how many of those have a Compose backend in src/Microsoft.AndroidX.Compose.Maui/Handlers/.
  • Property-mapper keys covered — finer-grained signal across every property key on every covered handler. This is the most useful single number for tracking "behavioural completeness" of individual handlers over time.

• Per-category coverage — handlers grouped into Pages / Navigation, Containers, Leaves, Menus / Toolbar, Shapes, App / Window, Other / advanced. Each row shows handler coverage and key coverage for the bucket.

• Per-handler coverage — single table, sorted by category, with a ✅ / 🟡 / ❌ status icon for every stock handler. ✅ = all keys covered, 🟡 = partial, ❌ = no Compose backend at all.

• Missing handlers worth investigating — ❌ handlers sorted by number of stock keys (biggest gaps first). These are the highest- leverage candidates for new handler work.

• Partial handlers (gap analysis) — 🟡 handlers sorted by coverage % (lowest first), listing the specific missing keys. This is the prioritised TODO list for tightening existing handlers.

• Per-handler property detail — one section per stock handler. Missing keys are listed inline; the full [x]/[ ] stock-key list is in a collapsed <details> block to keep the report skimmable.

• Microsoft.AndroidX.Compose.Maui-only handlers — internal plumbing handlers with no stock counterpart.

• Caveats — the matching heuristics in plain English. Always worth a re-read before drawing conclusions from a number — in particular, ViewHandler.ViewMapper is shared via RemapForCompose() so every Compose-backed handler gets Opacity/Scale*/Rotation* /etc. "for free", and CommandMapper keys (focus, scroll-to, …) aren't included.

Don't do these things

• Don't hand-edit docs/maui-coverage.md. It's regenerated every run and your edit will be lost.
• Don't add obj/maui-coverage/ to git — it's already covered by the root obj/ gitignore entry and contains the full decompiled MAUI Core handler source.
• Don't run the script from inside a subdirectory; paths in the script (obj/maui-coverage, docs/maui-coverage.md, src/Microsoft.AndroidX.Compose.Maui/Handlers/, Directory.Build.targets) are relative to the repo root.
• Don't compare coverage % across MAUI version bumps without first wiping obj/maui-coverage/ — the cache is keyed by handler class name, not by MAUI version.