add support for ALTER TABLE drop actions

Sources/FluentPostgreSQL/PostgreSQLDatabase+QuerySupporting.swift

@@ -115,25 +115,4 @@ extension PostgreSQLDatabase: QuerySupporting {
 
         return conn.future(model)
     }
-
-    /// See `SchemaSupporting`.
-    public static func schemaExecute(_ fluent: FluentPostgreSQLSchema, on conn: PostgreSQLConnection) -> Future<Void> {
-        let query: PostgreSQLQuery
-        switch fluent.statement {
-        case ._createTable:
-            var createTable: PostgreSQLCreateTable = .createTable(fluent.table)
-            createTable.columns = fluent.columns
-            createTable.tableConstraints = fluent.constraints
-            query = ._createTable(createTable)
-        case ._alterTable:
-            var alterTable: PostgreSQLAlterTable = .alterTable(fluent.table)
-            alterTable.columns = fluent.columns
-            alterTable.constraints = fluent.constraints
-            query = ._alterTable(alterTable)
-        case ._dropTable:
-            let dropTable: PostgreSQLDropTable = .dropTable(fluent.table)
-            query = ._dropTable(dropTable)
-        }
-        return conn.query(query).transform(to: ())
-    }
 }

Sources/FluentPostgreSQL/PostgreSQLDatabase+SchemaSupporting.swift

@@ -24,6 +24,34 @@ extension PostgreSQLDatabase: SchemaSupporting {
     /// See `SchemaSupporting`.
     public typealias SchemaReferenceAction = PostgreSQLForeignKeyAction
 
+    /// See `SchemaSupporting`.
+    public static func schemaExecute(_ fluent: FluentPostgreSQLSchema, on conn: PostgreSQLConnection) -> Future<Void> {
+        let query: PostgreSQLQuery
+        switch fluent.statement {
+        case ._createTable:
+            var createTable: PostgreSQLCreateTable = .createTable(fluent.table)
+            createTable.columns = fluent.columns
+            createTable.tableConstraints = fluent.constraints
+            query = ._createTable(createTable)
+        case ._alterTable:
+            var alterTable: PostgreSQLAlterTable = .alterTable(fluent.table)
+            alterTable.columns = fluent.columns
+            alterTable.constraints = fluent.constraints
+            alterTable.dropActions += fluent.deleteColumns.map { .init(.column, $0.identifier) }
+            alterTable.dropActions += fluent.deleteConstraints.map {
+                guard let id = $0.identifier else {
+                    fatalError("Cannot drop constraint without identifier: \($0).")
+                }
+                return .init(.constraint, id)
+            }
+            query = ._alterTable(alterTable)
+        case ._dropTable:
+            let dropTable: PostgreSQLDropTable = .dropTable(fluent.table)
+            query = ._dropTable(dropTable)
+        }
+        return conn.query(query).transform(to: ())
+    }
+
     /// See `SchemaSupporting`.
     public static func schemaField(for type: Any.Type, isIdentifier: Bool, _ column: PostgreSQLColumnIdentifier) -> PostgreSQLColumnDefinition {
         var constraints: [PostgreSQLColumnConstraint] = []

Tests/FluentPostgreSQLTests/FluentPostgreSQLTests.swift

@@ -406,6 +406,59 @@ class FluentPostgreSQLTests: XCTestCase {
         XCTAssertEqual(b.id, 1)
     }
 
+    func testAlterDrop() throws {
+        struct A: PostgreSQLMigration {
+            static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.create(Planet.self, on: conn) { builder in
+                    builder.field(for: \.id)
+                }
+            }
+
+            static func revert(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.delete(Planet.self, on: conn)
+            }
+        }
+        struct B: PostgreSQLMigration {
+            static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.update(Planet.self, on: conn) { builder in
+                    builder.field(for: \.name)
+                    builder.deleteField(for: \.id)
+                }
+            }
+
+            static func revert(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.update(Planet.self, on: conn) { builder in
+                    builder.deleteField(for: \.name)
+                    builder.field(for: \.id)
+                }
+            }
+        }
+        struct C: PostgreSQLMigration {
+            static func prepare(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.update(Planet.self, on: conn) { builder in
+                    builder.unique(on: \.name)
+                }
+            }
+
+            static func revert(on conn: PostgreSQLConnection) -> Future<Void> {
+                return PostgreSQLDatabase.update(Planet.self, on: conn) { builder in
+                    builder.deleteUnique(from: \.name)
+                }
+            }
+        }
+
+        let conn = try benchmarker.pool.requestConnection().wait()
+        conn.logger = DatabaseLogger(database: .psql, handler: PrintLogHandler())
+        defer { benchmarker.pool.releaseConnection(conn) }
+
+        try A.prepare(on: conn).wait()
+        defer { try? A.revert(on: conn).wait() }
+        try B.prepare(on: conn).wait()
+        defer { try? B.revert(on: conn).wait() }
+        try C.prepare(on: conn).wait()
+        defer { try? C.revert(on: conn).wait() }
+    }
+
     static let allTests = [
         ("testBenchmark", testBenchmark),
         ("testNestedStruct", testNestedStruct),