Add a couple of useful Fluent keypath-taking SQLQueryString interpolations

Author: gwynne

Sources/SQLKitExtras/FluentSQLKitExtras/Expressions/SQLQueryString+FluentKeypaths.swift

@@ -0,0 +1,19 @@
+#if FluentSQLKitExtras
+import FluentKit
+import SQLKit
+
+extension SQLQueryString {
+    /// Allow specifying a Fluent keypath as an identifier interpolation in an `SQLQueryString`.
+    @inlinable
+    public mutating func appendInterpolation(ident: KeyPath<some Schema, some QueryAddressableProperty>) {
+        self.appendInterpolation(.identifier(ident))
+    }
+
+    /// Allow specifying a Fluent keypath as an column interpolation in an `SQLQueryString`.
+    @inlinable
+    public mutating func appendInterpolation(col: KeyPath<some Schema, some QueryAddressableProperty>) {
+        self.appendInterpolation(.column(col))
+    }
+}
+#endif
+

Tests/SQLKitExtrasTests/FluentSQLKitExtrasTests.swift

@@ -306,6 +306,12 @@ struct FluentSQLKitExtrasTests {
             #expect(MockSQLDatabase(dialect: "mysql").serialize(.cast(\FooModel.$field, to: "text")).sql == #"CAST("foos"."field" AS text)"#)
             #expect(MockSQLDatabase(dialect: "postgresql").serialize(.cast(\FooModel.$field, to: "text")).sql == #"CAST("foos"."field" AS "text")"#)
         }
+
+        @Test
+        func queryStringExpression() {
+            #expect(serialize("foo \(ident: \FooModel.$field) bar" as SQLQueryString) == #"foo "field" bar"#)
+            #expect(serialize("foo \(col: \FooModel.$field) bar" as SQLQueryString) == #"foo "foos"."field" bar"#)
+        }
     }
 }