feat: compare_schemas command + diff staging into the changes queue (Task 15)

desktop/src/lib/commands.ts

@@ -2,6 +2,7 @@ import { invoke } from "@tauri-apps/api/core";
 import type { Connection, ConnectionInput, ConnectionTestResult, Folder, FolderInput, Tag, TagInput, Settings, ImportResult, TableInfo, QueryResult, BackupOptions, RestoreOptions, SyncOptions, PgToolStatus, MySqlToolStatus, MySqlBackupOptions, MySqlRestoreOptions, SqliteBackupOptions, SqliteRestoreOptions, FunctionInfo, TriggerInfo, SequenceInfo, EnumInfo, ExtensionInfo, SchemaGraph, IndexInfo, ConstraintInfo, RecentConnection, ObjectSearchHit, DependencyInfo, RoleInfo, PrivilegeEntry, RebuildReadiness, MaintenanceResult, TablespaceInfo, ColumnInfo, HypertableListResponse, MultiQueryResult } from "./types";
 import type { FilterRule, SortRule } from "../stores/dbViewerStore";
 import type { ChangePayload } from "./changePayload";
+import type { DiffReport } from "./types";
 import { buildObjectDdl as buildObjectDdlImpl, type ObjectKind, type DdlParams } from "./objectCrud";
 
 export { type ObjectKind, type DdlParams };
@@ -418,4 +419,14 @@ export async function getTablespaces(connectionId: string): Promise<TablespaceIn
 }
 export async function buildRebuildScript<C extends { name: string; type: string; nullable: boolean; default: string | null; is_pk: boolean }[]>(connectionId: string, schema: string, table: string, newColumns: C): Promise<string> {
   return invoke<string>("build_rebuild_script", { connectionId, schema, table, newColumns });
-}
+}
+export async function compareSchemas(
+  sourceConnectionId: string,
+  sourceSchema: string,
+  targetConnectionId: string,
+  targetSchema: string,
+): Promise<DiffReport> {
+  return invoke<DiffReport>("compare_schemas", {
+    sourceConnectionId, sourceSchema, targetConnectionId, targetSchema,
+  });
+}

desktop/src/lib/types.ts

@@ -506,4 +506,25 @@ export interface Relationship {
 export interface SchemaGraph {
   tables: TableNode[];
   relationships: Relationship[];
-}
+}
+export interface DiffDetailLine {
+  label: string;
+  old: string;
+  new: string;
+}
+
+export interface DiffItem {
+  object_type: string;
+  name: string;
+  kind: "added" | "removed" | "changed";
+  detail: DiffDetailLine[];
+  sync_sql: string[];
+  destructive: boolean;
+}
+
+export interface DiffReport {
+  items: DiffItem[];
+  source_label: string;
+  target_label: string;
+  truncated: boolean;
+}

desktop/src/stores/dbViewerStore.diff.test.ts

@@ -0,0 +1,30 @@
+import { describe, it, expect, beforeEach } from "vitest";
+import { useDbViewerStore } from "./dbViewerStore";
+import type { DiffItem } from "../lib/types";
+
+const item = (name: string, sql: string, destructive: boolean): DiffItem => ({
+  object_type: "table",
+  name,
+  kind: "added",
+  detail: [],
+  sync_sql: [sql],
+  destructive,
+});
+
+describe("addDiffItems", () => {
+  beforeEach(() => useDbViewerStore.getState().clearChanges());
+
+  it("stages one ddl change per non-destructive item, skipping destructive and empty", () => {
+    const items = [
+      item("users", "CREATE TABLE users (id int);", false),
+      item("old", "DROP TABLE old;", true),
+      { ...item("weird", "", false), sync_sql: [] },
+    ];
+    useDbViewerStore.getState().addDiffItems(items);
+    const queue = useDbViewerStore.getState().changesQueue;
+    expect(queue).toHaveLength(1);
+    expect(queue[0].type).toBe("ddl");
+    expect(queue[0].sql).toBe("CREATE TABLE users (id int);");
+    expect(queue[0].description).toContain("users");
+  });
+});

desktop/src/stores/dbViewerStore.ts

@@ -1,5 +1,5 @@
 import { create } from "zustand";
-import type { QueryResult, TableInfo, ChangeItemType, FunctionInfo, TriggerInfo, SequenceInfo, EnumInfo, ExtensionInfo, HypertableInfo, IndexInfo, ConstraintInfo, ObjectType, RoleInfo, MultiQueryResult } from "../lib/types";
+import type { QueryResult, TableInfo, ChangeItemType, FunctionInfo, TriggerInfo, SequenceInfo, EnumInfo, ExtensionInfo, HypertableInfo, IndexInfo, ConstraintInfo, ObjectType, RoleInfo, MultiQueryResult, DiffItem } from "../lib/types";
 import { getDatabases, getSchemas, getTables } from "../lib/commands";
 import type { ObjectKind, DdlParams } from "../lib/objectCrud";
 
@@ -169,6 +169,7 @@ interface DbViewerState {
     rows?: unknown[][];
     description?: string | null;
   }) => void;
+  addDiffItems: (items: DiffItem[]) => void;
   cancelChange: (changeId: string) => void;
   removeChange: (changeId: string) => void;
   updateChange: (changeId: string, patch: Partial<QueueItem>) => void;
@@ -549,6 +550,19 @@ export const useDbViewerStore = create<DbViewerState>((set, get) => ({
     set((state) => ({ changesQueue: [...state.changesQueue, item] }));
   },
 
+  addDiffItems: (items) => {
+    for (const it of items) {
+      if (it.destructive || it.sync_sql.length === 0) continue;
+      for (const sql of it.sync_sql) {
+        get().addChange({
+          type: "ddl",
+          sql,
+          description: `Schema diff: ${it.object_type} ${it.name} (${it.kind})`,
+        });
+      }
+    }
+  },
+
   cancelChange: (changeId) =>
     set((state) => ({
       changesQueue: state.changesQueue.map((c) =>