feat(zbugs-swift): port issueListCount and show the list's count

apps/zbugs-swift/Sources/ZBugs/Queries.swift

@@ -178,6 +178,13 @@ public struct IssueListV2Args: Codable, Sendable, Hashable {
   }
 }
 
+public struct IssueListCountArgs: Codable, Sendable, Hashable {
+  public var listContext: ListContextParams
+  public init(listContext: ListContextParams) {
+    self.listContext = listContext
+  }
+}
+
 public struct ListIssueByIDArgs: Codable, Sendable, Hashable {
   public var listContext: ListContextParams
   public var idField: IDField
@@ -375,6 +382,13 @@ public enum Queries {
   }
 
   /// One issue, for the order to start a list at.
+  /// The number of issues in the list: the same filters and permissions as
+  /// `issueListV2`, reduced to a `count()`.
+  public static let issueListCount = defineQuery("issueListCount") {
+    (args: IssueListCountArgs, auth: AuthData?) in
+    filterListQuery(zql.issue, args.listContext, auth?.role).count()
+  }
+
   public static let listIssueByID = defineQuery("listIssueByID") {
     (args: ListIssueByIDArgs, auth: AuthData?) in
     buildListQuery(ListQueryArgs(listContext: args.listContext, role: auth?.role))
@@ -421,7 +435,8 @@ public enum Queries {
   /// Every query, for the server's registry and the drift test.
   public static let all: [any NamedQuery<AuthData?>] = [
     allLabels, allUsers, allProjects, user, crewUser, labels, labelsOrderByName, issuePreloadV2,
-    userPref, usersForProject, commentsPage, comment, issueDetail, issueListV2, listIssueByID,
+    userPref, usersForProject, commentsPage, comment, issueDetail, issueListV2, issueListCount,
+    listIssueByID,
     emojiChange, prevNext, issueList, userPicker,
   ]
 }
@@ -483,8 +498,6 @@ func buildListQuery(_ args: ListQueryArgs) -> Query<Issue, [Issue]> {
   guard let listContext = args.listContext else {
     return alwaysFalse(q)
   }
-  let projectName = (listContext.projectName ?? zeroProjectName).lowercased()
-  q = q.whereExists(\.project, scalar: true) { $0.where(\.lowerCaseName, projectName) }
 
   let dir: AST.Direction =
     args.dir == .forward
@@ -502,6 +515,17 @@ func buildListQuery(_ args: ListQueryArgs) -> Query<Issue, [Issue]> {
     q = q.limit(limit)
   }
 
+  return filterListQuery(q, listContext, args.role)
+}
+
+/// Narrows `q` to the issues `listContext` selects that `role` may see
+/// (`filterListQuery`): shared by the list and its count.
+func filterListQuery(
+  _ q: Query<Issue, [Issue]>, _ listContext: ListContextParams, _ role: Role?
+) -> Query<Issue, [Issue]> {
+  let projectName = (listContext.projectName ?? zeroProjectName).lowercased()
+  var q = q.whereExists(\.project, scalar: true) { $0.where(\.lowerCaseName, projectName) }
+
   let text = truthy(listContext.textFilter).map { "%\(escapeLike($0))%" }
   q = q.where { issue in
     issue.and(
@@ -532,7 +556,7 @@ func buildListQuery(_ args: ListQueryArgs) -> Query<Issue, [Issue]> {
   if let assignee = truthy(listContext.assignee) {
     q = q.whereExists(\.assignee, scalar: true) { $0.where(\.login, assignee) }
   }
-  return applyIssuePermissions(q, args.role)
+  return applyIssuePermissions(q, role)
 }
 
 extension Query {

apps/zbugs-swift/Sources/ZBugsUI/IssueList.swift

@@ -67,6 +67,58 @@
     }
   }
 
+  /// The number of issues in the list, as zbugs' list page shows it: the
+  /// server's `issueListCount` once it has counted the list, in this session
+  /// or a previous one, and until then the list's running total. A text
+  /// search isn't counted: matching it checks every issue's comments, and it
+  /// changes with every keystroke.
+  struct IssueCount: View {
+    let filter: IssueFilter
+    let list: IssueVirtualizer?
+
+    var body: some View {
+      if filter.text.isEmpty {
+        SyncedIssueCount(filter: filter, list: list)
+      } else {
+        IssueCountLabel(synced: nil, list: list)
+      }
+    }
+  }
+
+  private struct SyncedIssueCount: View {
+    let list: IssueVirtualizer?
+    @ZeroQuery<Issue, Int, AuthData?> var count: Int
+
+    init(filter: IssueFilter, list: IssueVirtualizer?) {
+      self.list = list
+      _count = ZeroQuery(
+        Queries.issueListCount(IssueListCountArgs(listContext: filter.listContext)),
+        ttl: .defaultTTL)
+    }
+
+    var body: some View {
+      let counted = $count.resultType == .complete || $count.resultType == .cached
+      IssueCountLabel(synced: counted ? count : nil, list: list)
+    }
+  }
+
+  private struct IssueCountLabel: View {
+    let synced: Int?
+    let list: IssueVirtualizer?
+
+    var body: some View {
+      let s = list?.snapshot
+      let total = synced ?? s?.total
+      if let total {
+        Text(total.formatted()).accessibilityIdentifier("IssueCount")
+      } else if let s, s.complete || s.estimatedTotal > 0 {
+        // Rounded down to 50 above 50, as the list page does.
+        let e = s.estimatedTotal
+        Text("\((e < 50 ? e : e - e % 50).formatted())+").accessibilityIdentifier("IssueCount")
+      }
+    }
+  }
+
   /// The issue list in SwiftUI.
   struct IssueList: View {
     let list: IssueVirtualizer

apps/zbugs-swift/Sources/ZBugsUI/RootView.swift

@@ -194,6 +194,11 @@
     }
 
     @ToolbarContentBuilder private var toolbar: some ToolbarContent {
+      ToolbarItem {
+        IssueCount(filter: filter, list: issues)
+          .foregroundStyle(.secondary)
+          .monospacedDigit()
+      }
       ToolbarItem {
         ConnectionBadge(connection: model.zero.connection)
       }

apps/zbugs-swift/Tests/ZBugsTests/DriftTests.swift

@@ -13,8 +13,6 @@ import ZeroTesting
         .appendingPathComponent("drift-vectors.json"), encoding: .utf8)
     let failures = try Drift.failures(
       vectors: vectors, schema: .zbugs, queries: Queries.all, mutators: Mutators.all)
-    // Not ported yet: issueListCount is a count(), and the Swift client has no
-    // aggregates. Exact, so this fails once it is ported and must be removed.
-    #expect(failures == ["query issueListCount: no Swift definition"])
+    #expect(failures == [])
   }
 }