refactor(overlay): read the host tree through a HostTree interface

[NathanWalker]

What and why

The shared base for #199 (Angular Native) and #16 (NativeScript). Both pull requests change the same collectors to walk a HostTree instead of the DOM, so they conflict with each other. With this landed first, each one rebases onto one shared interface and keeps only its own platform code.

The two commits come from #199, unchanged and with their author kept:

• refactor(overlay): read the host tree through a HostTree interface is feat(overlay): add an Angular Native overlay #199's first commit. The component, injector and NgRx collectors walk a HostTree (roots, children, parent, tag, connected, isHost, optional selector and anchors). domTree() is the default and keeps the shadow DOM walk, <ng-container> anchors and selectors from main.
• refactor(overlay): let the signal graph and NgRx overlay take a HostTree holds the parts of feat(overlay): add an Angular Native overlay #199's second commit that involve no platform. The signal graph accepts a HostTree, installSignalWriteHook moves to signal-history.ts (the overlay still re-exports it), attachNgrx takes { tree, describe } options, and hostBySelector() finds a host by selector on any tree.

Nothing changes for browser pages: every caller keeps the DOM default, and no export or option is added to the package.

Refs #198

How it was verified

• pnpm commit:check (commit messages follow the guidelines)
• pnpm format:check
• pnpm typecheck (includes the ngc template checks)
• pnpm test:devtools (1072 passed)
• pnpm skills:check (when .claude/ changed) — not changed
• Docs in apps/docs updated — no user-facing change, so no docs (no-docs)
• pnpm extension:build — app/ not changed
• Checked in the browser with axe — no UI change

Notes for reviewers

• After this lands, feat(overlay): add an Angular Native overlay #199 keeps the Angular Native overlay, panel view, docs and example, and feat: NativeScript support (native overlay, example app, standalone server fixes) #16 drops its own HostTree and collector changes and ports its NativeScript tree to this interface.
• A possible next step: move the connection, retry and session code both overlays duplicate into a shared module, so each platform supplies only its tree, highlight and startup hook.

Summary by CodeRabbit

• New Features
  • Angular DevTools can now inspect component, injector, NgRx, and signal data on rendering platforms that don’t use a DOM.
  • DOM inspection now accounts for Angular roots and open shadow roots, with optional ng-container anchors.
• Documentation
  • Added guidance on host trees and platform-independent inspection terminology.

[coderabbitai]

Navigate logical layers of code changes, visualize relationships, and explore their blast radius.

🧰 Additional context used

📚 Code guidelines (1)

AGENTS.md — auto-discovered

📝 Walkthrough

Walkthrough

The PR adds a generic HostTree abstraction with a DOM adapter and updates component, injector, NgRx, and signal-graph collectors to accept host trees. It also adds host-tree tests and moves signal-write hook installation from overlay.ts to signal-history.ts.

Changes

Host Tree Collection

Layer / File(s)	Summary
Host tree and DOM adapter docs/CONTEXT.md, docs/contributing/coding-standards.md, packages/ng-devtools/src/host-tree.ts, packages/ng-devtools/src/element-id.ts, packages/ng-devtools/src/dom-walk.ts, packages/ng-devtools/src/__tests__/host-tree.test.ts, packages/ng-devtools/src/__tests__/dom-walk.test.ts, packages/ng-devtools/src/defer-blocks.ts	Adds the HostTree contract and DOM helpers for roots, traversal, connectivity, selectors, and optional comment anchors. Generalizes element IDs to objects with configurable connectivity checks. Adds host-tree tests and updates the angularRoots import.
Component and injector collection packages/ng-devtools/src/component-tree.ts, packages/ng-devtools/src/injector-tree.ts, packages/ng-devtools/src/__tests__/host-tree-views.test.ts	Component and injector APIs now accept generic hosts and traverse a HostTree. The tests check component details, detached hosts, injector output, and traversal order.
NgRx collection and page options packages/ng-devtools/src/ngrx-collector.ts, packages/ng-devtools/src/ngrx-overlay.ts, packages/ng-devtools/src/__tests__/ngrx-collector.test.ts, packages/ng-devtools/src/__tests__/host-tree-views.test.ts	NgRx component discovery traverses host-tree roots and children. The overlay accepts optional tree and page-description options. Tests exercise host visitation and pass domTree() to the collector.
Signal graph host-tree support packages/ng-devtools/src/signal-graph.ts, packages/ng-devtools/src/__tests__/host-tree-views.test.ts	Signal-graph collection accepts a Document or HostTree. Tree-based target lookup uses connected hosts and tree selectors; tests cover collection for a selected synthetic host.

Signal Write Hook Extraction

Layer / File(s)	Summary
Signal-write hook implementation packages/ng-devtools/src/signal-history.ts, packages/ng-devtools/src/overlay.ts	Adds installSignalWriteHook and SignalSetHook to signal-history.ts. overlay.ts re-exports the installer and removes its local implementation.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Refactor

Sequence Diagram(s)

sequenceDiagram
  participant collectComponentTree
  participant HostTree
  participant ComponentDebugNg
  collectComponentTree->>HostTree: Read roots, children, tags, and connectivity
  collectComponentTree->>ComponentDebugNg: Read component data for each host
  collectComponentTree-->>HostTree: Return component tree details

Loading

Suggested labels: enhancement

Merge Risk: 🔵 Low · up to 571c1

Explicit cross-document tree use can report details for the wrong host. Scope the DOM adapter’s host checks to its document; the issue is bounded and does not block the default overlay workflow.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 571c1

The reviewed browser callers retain their default tree and hook lifecycle, with no demonstrated new attacker-controlled collection path. Risk remains low rather than minimal because cross-tree isolation and exact compatibility with the previous implementation are not fully established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The reviewed browser paths affect application component, injector, signal and NgRx store data, including store mutation through debugger commands. They do not demonstrate attacker-supplied HostTree callbacks or a newly exposed cross-service authority path; upstream transport authentication was not established by this focused review.

Trust Boundaries and Controls

• observed — Selector lookup traverses supplied tree roots and children, whereas ID lookup uses shared identity storage. A caller-provided tree must supply any stronger membership policy; the DOM adapter does not enforce per-document isolation.

Resilience and Maintainability Implications

• observed — The signal installer chains the previous hook, isolates recorder exceptions and deactivates recording on disposal. Disposal retains a subsequently installed hook rather than permanently replacing it. This supports shared-hook ownership, but does not establish behavior when the previous hook or hook setter throws.

Hardening Proposals

• proposed — Before using separate host trees as security or ownership boundaries, define explicit tree membership and scope ID lookup and pruning accordingly. Exercise simultaneous trees and foreign connected IDs so one collector cannot select another tree's hosts or invalidate its identity mappings.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 5.71% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 70 functions across 13 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: refactoring overlay collectors to access hosts through the shared HostTree interface.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 5.71% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 70 functions across 13 files. (2 skipped: 2 unsupported.)

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---

_{A rabbit hops through roots and leaves,
And maps the hosts beneath the eaves.
A signal hook now has its home,
While trees can grow beyond the DOM.
Tests trace each path from root to end,
Then curl up softly with a friend.}

_{Comment @coderabbitai help to get the list of available commands.}

[erkamyaman]

@NathanWalker I was just gonna pink you about this! Thank you

[NathanWalker]

One nice thing about different approaches is it informs a fundamental boundary line to make core of these tools even more robust and scalable 💯

[erkamyaman]

Thanks Nathan, this is a clean base for both platforms. I pushed one small commit on top (571c1c0):

• hostBySelector and the NgRx collector reversed the arrays from roots() and children() in place, so a HostTree that returns its own arrays got reordered on every walk. Both copy first now.
• Tests for hostBySelector and for the signal graph over a HostTree.
• CONTEXT.md and the coding standards list the signal graph among the collectors that walk the host tree.

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☁️ Nx Cloud last updated this comment at 2026-10-02 17:31:20 UTC

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Actionable comments posted: 1

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Inline comments:
Review comments at @packages/ng-devtools/src/host-tree.ts:
- Around line 113-122: Update domTree(doc)’s isHost and connected callbacks to
accept hosts only when their ownerDocument is doc, while preserving the existing
element, comment, and anchors checks.

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ℹ️ Review info

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Configuration used: Organization UI

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Run ID: 4302b7f3-80c7-422c-b317-009b5f4e7174

📥 Commits

Reviewing files that changed from the base of the PR and between 78a0392 and 571c1c0.

📒 Files selected for processing (17)

• docs/CONTEXT.md
• docs/contributing/coding-standards.md
• packages/ng-devtools/src/__tests__/dom-walk.test.ts
• packages/ng-devtools/src/__tests__/host-tree-views.test.ts
• packages/ng-devtools/src/__tests__/host-tree.test.ts
• packages/ng-devtools/src/__tests__/ngrx-collector.test.ts
• packages/ng-devtools/src/component-tree.ts
• packages/ng-devtools/src/defer-blocks.ts
• packages/ng-devtools/src/dom-walk.ts
• packages/ng-devtools/src/element-id.ts
• packages/ng-devtools/src/host-tree.ts
• packages/ng-devtools/src/injector-tree.ts
• packages/ng-devtools/src/ngrx-collector.ts
• packages/ng-devtools/src/ngrx-overlay.ts
• packages/ng-devtools/src/overlay.ts
• packages/ng-devtools/src/signal-graph.ts
• packages/ng-devtools/src/signal-history.ts

💤 Files with no reviewable changes (2)

• packages/ng-devtools/src/dom-walk.ts
• packages/ng-devtools/src/tests/dom-walk.test.ts

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[erkamyaman]

@all-contributors please add @NathanWalker for code

[allcontributors]

@erkamyaman

I've put up a pull request to add @NathanWalker! 🎉