test(mcp-server): selection requests, get_selection texts, and page screenshots that leave the view alone

Unit tests for the request plumbing (random id, one answer, timeout), the tool's texts (cells, nothing selected, external draw.io) and the shell's side (one answer per request, after draw.io is up, never during a projection); the wiring test starts a session with BROWSER=none to see the no-tab message. Shell e2e: cells selected in the editor reach get_selection; a PNG of another page differs from the page on screen, which stays.

tests/unit/mcp-sync-core.test.ts

@@ -8,6 +8,7 @@ import {
     type SyncStatus,
     tokenFromPage,
 } from "@/packages/mcp-server/shell/mcp-sync-core"
+import type { SelectionAnswer } from "@/packages/mcp-server/src/selection"
 
 // The shell's side of the MCP server protocol, driven step by step with a
 // stubbed server (fetch) and canvas, as tests/unit/mcp-preview-recovery.test.ts
@@ -59,7 +60,15 @@ function open(options: { currentPageId?: string | null } = {}) {
     const notices: SyncNotice[] = []
     const statuses: SyncStatus[] = []
     let recreated = 0
-    const canvas = { xml: "", pageId: options.currentPageId ?? null }
+    const canvas: {
+        xml: string
+        pageId: string | null
+        selection: SelectionAnswer
+    } = {
+        xml: "",
+        pageId: options.currentPageId ?? null,
+        selection: { pageId: "p1", pageName: "Page-1", cells: [] },
+    }
     const sync = createMcpSync({
         sessionId: "mcp-test",
         apiBase: "/api",
@@ -86,6 +95,7 @@ function open(options: { currentPageId?: string | null } = {}) {
                 }),
             currentXml: () => canvas.xml,
             currentPageId: () => canvas.pageId,
+            readSelection: () => canvas.selection,
         },
         onNotice: (notice) => notices.push(notice),
         onStatus: (status) => statuses.push(status),
@@ -863,6 +873,130 @@ describe("MCP sync export requests", () => {
     })
 })
 
+describe("MCP sync selection requests (get_selection)", () => {
+    const selectionState = (extra: Record<string, unknown> = {}) =>
+        state("S1", 2, "<mxfile>A</mxfile>", { selectionId: "sel-1", ...extra })
+    const picked: SelectionAnswer = {
+        pageId: "p1",
+        pageName: "Page-1",
+        cells: [
+            {
+                id: "3",
+                label: "Login",
+                edge: false,
+                geometry: { x: 100, y: 100, width: 120, height: 60 },
+            },
+            { id: "5", label: "", edge: true, source: "3", target: "4" },
+        ],
+    }
+
+    it("answers a request once, with what the editor has selected", async () => {
+        const t = await inStep()
+        t.canvas.selection = picked
+        const poll = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await poll
+        const answer = t.next("POST")
+        expect(answer.body).toEqual({
+            sessionId: "mcp-test",
+            selectionId: "sel-1",
+            selection: picked,
+        })
+        answer.answer({ status: 200, body: { success: true } })
+        // The server still shows the request on the next poll: not again
+        const again = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await again
+        expect(t.posts()).toHaveLength(0)
+        // A new request is answered
+        t.canvas.selection = { pageId: "p1", pageName: "Page-1", cells: [] }
+        const later = t.sync.poll()
+        t.next("GET").answer(selectionState({ selectionId: "sel-2" }))
+        await later
+        expect(t.next("POST").body).toMatchObject({
+            selectionId: "sel-2",
+            selection: { cells: [] },
+        })
+    })
+
+    it("says when the page cannot reach the editor", async () => {
+        const t = await inStep()
+        t.canvas.selection = {
+            pageId: null,
+            pageName: null,
+            cells: [],
+            unavailable: true,
+        }
+        const poll = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await poll
+        expect(t.next("POST").body.selection).toEqual({
+            pageId: null,
+            pageName: null,
+            cells: [],
+            unavailable: true,
+        })
+    })
+
+    it("waits until draw.io is up, where the editor is reached", async () => {
+        const t = open()
+        t.canvas.selection = picked
+        let poll = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await poll
+        expect(t.posts()).toHaveLength(0)
+        t.sync.setReady(true)
+        // The thumbnail of the write loaded before draw.io was ready
+        t.nextExport().answer(null)
+        await t.settle()
+        poll = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await poll
+        expect(t.next("POST").body).toMatchObject({
+            selectionId: "sel-1",
+            selection: picked,
+        })
+    })
+
+    it("never answers while a projection is on screen", async () => {
+        const t = await inStep()
+        t.canvas.selection = picked
+        // A projection shows another page: its selection is not the user's
+        let poll = t.sync.poll()
+        t.next("GET").answer(
+            selectionState({
+                exportFormat: "svg",
+                exportId: "e1",
+                exportXml: "<mxfile>page 2 only</mxfile>",
+            }),
+        )
+        await poll
+        expect(t.sync.read().projectionActive).toBe(true)
+        expect(t.posts()).toHaveLength(0)
+        // The export answers and the document comes back
+        await vi.advanceTimersByTimeAsync(600)
+        t.nextExport().answer({ data: "<svg>page 2</svg>" })
+        await t.settle()
+        t.next("POST").answer({ status: 200, body: { success: true } })
+        await t.settle()
+        await t.settle()
+        t.next("GET").answer(selectionState())
+        await t.settle()
+        await t.settle()
+        expect(t.posts()).toHaveLength(0)
+        t.sync.onDrawioLoad()
+        expect(t.sync.read().projectionActive).toBe(false)
+        // The request is still pending: answered now
+        poll = t.sync.poll()
+        t.next("GET").answer(selectionState())
+        await poll
+        expect(t.next("POST").body).toMatchObject({
+            selectionId: "sel-1",
+            selection: picked,
+        })
+    })
+})
+
 describe("MCP sync History", () => {
     const historyList = {
         status: 200,