feat(docs): Add docs for Appset UI

docs/operator-manual/applicationset/Web-UI.md

@@ -0,0 +1,238 @@
+# ApplicationSet Web UI
+
+> [!WARNING]
+> **Alpha Feature (Since v3.5.0)**
+>
+> This is an [alpha](https://github.com/argoproj/argoproj/blob/main/community/feature-status.md#alpha) feature.
+> The look, behavior, and APIs it consumes may change in future releases or be removed in backwards-incompatible ways.
+
+Argo CD introduces a first-class Web UI for ApplicationSets. Until now,
+ApplicationSets were managed primarily through `kubectl`, the
+`argocd appset` CLI, or by browsing the generated child Applications. The
+new UI surfaces ApplicationSets directly, with a list view, a resource
+tree, a slide-out details panel, and a preview tab that lets you see what
+Applications an ApplicationSet will generate.
+
+## ApplicationSets list page
+
+The new `/applicationsets` page is the entry point. It lives next to the
+existing Applications list and shares the same filtering, search, and
+view-preferences, so it should feel familiar.
+
+You can reach it from the top-level navigation, or directly at
+`https://<your-argocd>/applicationsets`.
+
+![ApplicationSets list page](../../assets/applicationset/Web-UI/applicationsets-list.png)
+
+What's on the page:
+
+- **Search bar** — fuzzy-matches against name and namespace. Use the
+  keyboard shortcut `/` to focus it.
+- **Filters sidebar** — filter by project, namespace, labels, and
+  ApplicationSet health status (`Healthy`, `Progressing`, `Degraded`,
+  `Unknown`). Filters are reflected in the URL so they can be shared or
+  bookmarked.
+- **Health summary** — a pie chart at the top summarizes the health of
+  ApplicationSets matching the current filter.
+- **Tile / table views** — toggle between a tile grid and a table view.
+  The table view shows name, namespace, project, health, conditions, and
+  the number of generated Applications.
+
+> [!TIP]
+> The page shows ApplicationSets across every namespace your user has
+> access to. RBAC is enforced exactly as on the CLI — if you can `get` an
+> ApplicationSet from `argocd appset get`, you can see it here.
+
+## ApplicationSet resource tree
+
+Selecting an ApplicationSet from the list opens its details page. The
+center of the page is a **resource tree** that visualizes the
+ApplicationSet and the child Applications it generates.
+
+![ApplicationSet resource tree](../../assets/applicationset/Web-UI/appset-resource-tree.png)
+
+Things to know:
+
+- The root node is the ApplicationSet itself. Each downstream node is a
+  child Application generated by the ApplicationSet.
+- Health and sync status icons render on each node the same way they do
+  on the Application resource tree.
+- Clicking a child Application navigates to that Application's own
+  details page.
+
+## Status bar: health, conditions, age
+
+The top of the ApplicationSet details page shows a status bar summarizing
+the ApplicationSet at a glance: its **health**, the count of
+**conditions** by severity, and **last updated**.
+
+![ApplicationSet status bar](../../assets/applicationset/Web-UI/appset-status-bar.png)
+
+### How health is derived
+
+The ApplicationSet controller now writes a `status.health` field on the
+ApplicationSet CR (with `status` and `message`), computed from the
+ApplicationSet's `status.conditions`. The UI reads this field directly.
+
+The rules the controller applies, in order:
+
+1. If `status.conditions` is empty → **Unknown**
+   (`"No status conditions found for ApplicationSet"`).
+2. If an `ErrorOccurred` condition has `status: True`
+   → **Degraded**, with the condition's message.
+3. Otherwise, if a `RolloutProgressing` condition has `status: True`
+   → **Progressing**, with the condition's message.
+4. Otherwise, if a `ResourcesUpToDate` condition has `status: True`
+   → **Healthy**, with the condition's message.
+5. Otherwise → **Unknown** (`"Waiting for health status to be determined"`).
+
+### How conditions are shown
+
+![ApplicationSet conditions modal](../../assets/applicationset/Web-UI/appset-conditions.png)
+
+The conditions modal shows each condition's **type**, **status**, the
+**message** reported by the controller and **when** it was last reported.
+This is usually the first place to look when an ApplicationSet shows up
+as **Degraded** or **Unknown**.
+
+## Slide-out panel: Summary, Manifest, Events, Preview
+
+Clicking the ApplicationSet node (or any node on the tree) opens a
+slide-out panel from the right edge of the screen — the same pattern used
+elsewhere in Argo CD for resource details.
+
+### Summary
+
+Shows metadata at a glance: name, namespace, creation timestamp,
+health, conditions, labels, annotations, and sync policy.
+
+![Summary tab](../../assets/applicationset/Web-UI/summary-tab.png)
+
+If the ApplicationSet has conditions, the **CONDITIONS** row links to a
+detailed conditions view so you can see warnings or errors raised by the
+controller (for example, a generator that failed to evaluate).
+
+### Manifest
+
+A read-only YAML view of the ApplicationSet's `spec`.
+
+### Events
+
+Kubernetes events for the ApplicationSet — useful when investigating why
+a particular generator parameter set produced (or failed to produce) an
+Application.
+
+### Preview
+
+The Preview tab is the most significant new capability. It is covered in
+detail in the next section.
+
+## Preview: see what your ApplicationSet will generate
+
+The **PREVIEW** tab mirrors the `argocd appset generate` CLI command in
+the browser. It shows you the Applications an ApplicationSet would
+generate right now. When you edit the spec a diff between the
+proposed output and what is currently live.
+
+![Preview tab demo](../../assets/applicationset/Web-UI/preview-demo.gif)
+
+### How it works
+
+The Preview tab calls the existing
+`POST /api/v1/applicationsets/generate` endpoint, which the controller
+uses to render template output without persisting anything to the
+cluster.
+
+The result is rendered in three sub-tabs:
+
+| Tab            | Shows                                                                          |
+|----------------|--------------------------------------------------------------------------------|
+| `DIFF`         | The default tab. A unified diff of each Application that would change.         |
+| `LIVE APPS`    | The Applications currently generated by the ApplicationSet on the cluster.     |
+| `DESIRED APPS` | The Applications that *would* be generated if the proposed spec were applied.  |
+
+Each entry in `DIFF` represents one child Application and is categorized
+as added (only in `DESIRED APPS`), removed (only in `LIVE APPS`), or
+modified (present in both with field-level differences).
+
+### Editing the spec
+
+Click **Edit** on the ApplicationSet manifest card to make the YAML
+editable. Hit **Preview** again and the diff regenerates against your
+edits. Click **Cancel** to discard local edits.
+
+> [!IMPORTANT]
+> Edits in the Preview tab are **never saved**. The tab is a sandbox; to
+> persist a change you must update the ApplicationSet through your normal
+> GitOps flow (or via `kubectl apply` / `argocd appset create`).
+
+### Permissions
+
+Generating a preview requires `applicationsets, create` permission on
+the project of the ApplicationSet's template. If you don't have it, the
+Preview tab returns a clear permission-denied message instead of a diff.
+
+## Changes to Applications generated by an ApplicationSet
+
+For Applications that are generated by an ApplicationSet (i.e. that have
+an `ApplicationSet` `ownerReference`), the Application UI now shows two
+new things on the resource tree.
+
+### Owner badge
+
+A small badge labeled with the parent ApplicationSet's name
+appears on the Application node. Clicking it jumps directly to the
+ApplicationSet details page.
+
+![ApplicationSet owner badge on an Application](../../assets/applicationset/Web-UI/appset-owner-badge.png)
+
+### Show / hide parent ApplicationSet
+
+In the Application's view preferences, a new toggle —
+**Show parent ApplicationSet** — adds the parent ApplicationSet as a
+synthetic root node on the resource tree, with an edge to the
+Application. This is useful when you want a single view that includes
+both the ApplicationSet and the Application it produced.
+
+![Show parent ApplicationSet toggle](../../assets/applicationset/Web-UI/show-parent-toggle.png)
+
+When the toggle is on, the badge is hidden (since the parent is already
+rendered explicitly).
+
+### Per-Application preview from the app-of-appset pattern
+
+When you use the
+[app-of-ApplicationSets pattern](Use-Cases.md) — an Application whose
+resources include an ApplicationSet — the ApplicationSet node on the
+parent Application's tree now includes a preview feature in its slide-out
+panel. Selecting it opens a panel with a **Preview** experience similar
+to the one described above, scoped to the changes that would land when
+you sync the parent Application.
+
+![App-of-AppSet preview](../../assets/applicationset/Web-UI/app-of-appset-preview.png)
+
+There are two important differences from the standalone Preview tab:
+
+- **Desired state comes from Git, not an editor.** The proposed
+  ApplicationSet is the target manifest tracked by the parent
+  Application (i.e. what's in Git). There is no YAML editor in this panel.
+- **Only available when the ApplicationSet is OutOfSync.** If the parent
+  Application's ApplicationSet resource is already in sync, there is no
+  diff to show — the panel renders a short status message instead.
+
+This is the bridge between "I have a pending sync on my parent
+Application" and "show me which child Applications would change as a
+result."
+
+## Known limitations
+
+- The Preview tab compares whole Application manifests. It does **not**
+  recurse into the Kubernetes resources inside each child Application —
+  for that, sync the child Application and use the existing Application
+  diff view.
+- Generators that depend on external systems (Git, SCM Provider, Pull
+  Request, Cluster) are re-evaluated each time you click **Preview**. If
+  the upstream system is slow or flaky, the preview will reflect that.
+- The UI honors ApplicationSet RBAC. Users who cannot `create`
+  ApplicationSets in the target project will not be able to render a
+  preview, even if they can `get` the ApplicationSet.

docs/operator-manual/feature-maturity.md

@@ -25,6 +25,7 @@ to indicate their stability and maturity. These are the statuses of non-stable f
 | [Cluster Sharding: consistent-hashing][9] | v2.12.0    | Alpha  |
 | [Service Account Impersonation][10]       | v2.13.0    | Beta   |
 | [Source Hydrator][11]                     | v2.14.0    | Alpha  |
+| [ApplicationSet Web UI][12]               | v3.5.0     | Alpha  |
 
 ## Unstable Configurations
 
@@ -73,3 +74,4 @@ to indicate their stability and maturity. These are the statuses of non-stable f
 [9]: ./high_availability.md#argocd-application-controller
 [10]: app-sync-using-impersonation.md
 [11]: ../user-guide/source-hydrator.md
+[12]: applicationset/Web-UI.md

mkdocs.yml

@@ -129,6 +129,7 @@ nav:
     - Git File Generator Globbing: operator-manual/applicationset/Generators-Git-File-Globbing.md
     - ApplicationSet Specification Reference: operator-manual/applicationset/applicationset-specification.md
     - ApplicationSet in any namespace: operator-manual/applicationset/Appset-Any-Namespace.md
+    - ApplicationSet Web UI: operator-manual/applicationset/Web-UI.md
   - Server Configuration Parameters:
     - operator-manual/server-commands/argocd-server.md
     - operator-manual/server-commands/argocd-application-controller.md