Handle inline relations in result parsing.

+ Parse inline relations when parsing a query result.
+ Implement a custom pg.Mapper to pass the row manually.

src/postgresql.zig

@@ -59,8 +59,89 @@ pub fn handleRawPostgresqlError(err: anyerror, connection: *pg.Conn) anyerror {
 	}
 }
 
+fn isSlice(comptime T: type) ?type {
+	switch(@typeInfo(T)) {
+		.Pointer => |ptr| {
+			if (ptr.size != .Slice) {
+				@compileError("cannot get value of type " ++ @typeName(T));
+			}
+			return if (ptr.child == u8) null else ptr.child;
+		},
+		.Optional => |opt| return isSlice(opt.child),
+		else => return null,
+	}
+}
+
+fn mapValue(comptime T: type, value: T, allocator: std.mem.Allocator) !T {
+	switch (@typeInfo(T)) {
+		.Optional => |opt| {
+			if (value) |v| {
+				return try mapValue(opt.child, v, allocator);
+			}
+			return null;
+		},
+		else => {},
+	}
+
+	if (T == []u8 or T == []const u8) {
+		return try allocator.dupe(u8, value);
+	}
+
+	if (std.meta.hasFn(T, "pgzMoveOwner")) {
+		return value.pgzMoveOwner(allocator);
+	}
+
+	return value;
+}
+
+fn rowMapColumn(self: *const pg.Row, field: *const std.builtin.Type.StructField, optional_column_index: ?usize, allocator: ?std.mem.Allocator) !field.type {
+	const T = field.type;
+	const column_index = optional_column_index orelse {
+		if (field.default_value) |dflt| {
+			return @as(*align(1) const field.type, @ptrCast(dflt)).*;
+		}
+		return error.FieldColumnMismatch;
+	};
+
+	if (comptime isSlice(T)) |S| {
+		const slice = blk: {
+			if (@typeInfo(T) == .Optional) {
+				break :blk self.get(?pg.Iterator(S), column_index) orelse return null;
+			} else {
+				break :blk self.get(pg.Iterator(S), column_index);
+			}
+		};
+		return try slice.alloc(allocator orelse return error.AllocatorRequiredForSliceMapping);
+	}
+
+	const value = self.get(field.type, column_index);
+	const a = allocator orelse return value;
+	return mapValue(T, value, a);
+}
+
+pub fn PgMapper(comptime T: type) type {
+	return struct {
+		result: *pg.Result,
+		allocator: ?std.mem.Allocator,
+		column_indexes: [std.meta.fields(T).len]?usize,
+
+		const Self = @This();
+
+		pub fn next(self: *const Self, row: *pg.Row) !?T {
+			var value: T = undefined;
+
+			const allocator = self.allocator;
+			inline for (std.meta.fields(T), self.column_indexes) |field, optional_column_index| {
+				//TODO I must reimplement row.mapColumn because it's not public :-(
+				@field(value, field.name) = try rowMapColumn(row, &field, optional_column_index, allocator);
+			}
+			return value;
+		}
+	};
+}
+
 /// Make a PostgreSQL result mapper with the given prefix, if there is one.
-pub fn makeMapper(comptime T: type, result: *pg.Result, allocator: std.mem.Allocator, optionalPrefix: ?[]const u8) !pg.Mapper(T) {
+pub fn makeMapper(comptime T: type, result: *pg.Result, allocator: std.mem.Allocator, optionalPrefix: ?[]const u8) !PgMapper(T) {
 	var column_indexes: [std.meta.fields(T).len]?usize = undefined;
 
 	inline for (std.meta.fields(T), 0..) |field, i| {
@@ -80,21 +161,91 @@ pub fn makeMapper(comptime T: type, result: *pg.Result, allocator: std.mem.Alloc
 	};
 }
 
+/// PostgreSQL implementation of the query result reader.
 pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[]const _relations.ModelRelation) type {
 	const InstanceInterface = _result.QueryResultReader(TableShape, inlineRelations).Instance;
 
+	// Build relations mappers container type.
+	const RelationsMappersType = comptime typeBuilder: {
+		if (inlineRelations) |_inlineRelations| {
+			// Make a field for each relation.
+			var fields: [_inlineRelations.len]std.builtin.Type.StructField = undefined;
+
+			for (_inlineRelations, &fields) |relation, *field| {
+				// Get relation field type (TableShape of the related value).
+				var relationImpl = relation.relation{};
+				const relationInstanceType = @TypeOf(relationImpl.relation());
+				const relationFieldType = PgMapper(relationInstanceType.TableShape);
+
+				field.* = .{
+					.name = relation.field ++ [0:0]u8{},
+					.type = relationFieldType,
+					.default_value = null,
+					.is_comptime = false,
+					.alignment = @alignOf(relationFieldType),
+				};
+			}
+
+			// Build type with one field for each relation.
+			break :typeBuilder @Type(std.builtin.Type{
+				.Struct = .{
+					.layout = std.builtin.Type.ContainerLayout.auto,
+					.fields = &fields,
+					.decls = &[0]std.builtin.Type.Declaration{},
+					.is_tuple = false,
+				},
+			});
+		}
+
+		// Build default empty type.
+		break :typeBuilder @Type(std.builtin.Type{
+			.Struct = .{
+				.layout = std.builtin.Type.ContainerLayout.auto,
+				.fields = &[0]std.builtin.Type.StructField{},
+				.decls = &[0]std.builtin.Type.Declaration{},
+				.is_tuple = false,
+			},
+		});
+	};
+
 	return struct {
 		const Self = @This();
 
+		/// PostgreSQL implementation of the query result reader instance.
 		pub const Instance = struct {
 			/// Main object mapper.
-			mainMapper: pg.Mapper(TableShape) = undefined,
+			mainMapper: PgMapper(TableShape) = undefined,
+			relationsMappers: RelationsMappersType = undefined,
 
-			fn next(opaqueSelf: *anyopaque) !?TableShape { //TODO inline relations.
+			fn next(opaqueSelf: *anyopaque) !?_result.TableWithRelations(TableShape, inlineRelations) {
 				const self: *Instance = @ptrCast(@alignCast(opaqueSelf));
-				return try self.mainMapper.next();
+
+				// Try to get the next row.
+				var row: pg.Row = try self.mainMapper.result.next() orelse return null;
+
+				// Get main table result.
+				const mainTable = try self.mainMapper.next(&row) orelse return null;
+
+				// Initialize the result.
+				var result: _result.TableWithRelations(TableShape, inlineRelations) = undefined;
+
+				// Copy each basic table field.
+				inline for (std.meta.fields(TableShape)) |field| {
+					@field(result, field.name) = @field(mainTable, field.name);
 				}
 
+				if (inlineRelations) |_inlineRelations| {
+					// For each relation, retrieve its value and put it in the result.
+					inline for (_inlineRelations) |relation| {
+						//TODO detect null relation.
+						@field(result, relation.field) = try @field(self.relationsMappers, relation.field).next(&row);
+					}
+				}
+
+				return result; // Return built result.
+			}
+
+			/// Get the generic reader instance instance.
 			pub fn instance(self: *Instance, allocator: std.mem.Allocator) InstanceInterface {
 				return .{
 					.__interface = .{
@@ -115,9 +266,22 @@ pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[
 		fn initInstance(opaqueSelf: *anyopaque, allocator: std.mem.Allocator) !InstanceInterface {
 			const self: *Self = @ptrCast(@alignCast(opaqueSelf));
 			self.instance.mainMapper = try makeMapper(TableShape, self.result, allocator, null);
+
+			if (inlineRelations) |_inlineRelations| {
+				// Initialize mapper for each relation.
+				inline for (_inlineRelations) |relation| {
+					// Get relation field type (TableShape of the related value).
+					comptime var relationImpl = relation.relation{};
+					const relationInstanceType = @TypeOf(relationImpl.relation());
+					@field(self.instance.relationsMappers, relation.field) =
+						try makeMapper(relationInstanceType.TableShape, self.result, allocator, "relations." ++ relation.field ++ ".");
+				}
+			}
+
 			return self.instance.instance(allocator);
 		}
 
+		/// Get the generic reader instance.
 		pub fn reader(self: *Self) _result.QueryResultReader(TableShape, inlineRelations) {
 			return .{
 				._interface = .{

src/query.zig

@@ -43,8 +43,8 @@ pub fn RepositoryQuery(comptime Model: type, comptime TableShape: type, comptime
 
 			for (_with) |relation| {
 				// For each relation, determine if it's inline or not.
-				var tt = relation.relation{};
+				var relationImpl = relation.relation{};
-				const relationInstance = tt.relation();
+				const relationInstance = relationImpl.relation();
 				if (relationInstance.inlineMapping()) {
 					// Add the current relation to inline relations.
 					inlineRelations = @ptrCast(@constCast(_comptime.append(inlineRelations, relation)));

src/relations.zig

@@ -67,6 +67,10 @@ pub fn typedMany(
 	return struct {
 		const Self = @This();
 
+		fn getRepositoryConfiguration(_: *anyopaque) repository.RepositoryConfiguration(ToModel, ToTable) {
+			return toRepositoryConfig;
+		}
+
 		fn inlineMapping(_: *anyopaque) bool {
 			return false;
 		}
@@ -109,11 +113,12 @@ pub fn typedMany(
 			}
 		}
 
-		pub fn relation(self: *Self) Relation {
+		pub fn relation(self: *Self) Relation(ToModel, ToTable) {
 			return .{
 				._interface = .{
 					.instance = self,
 
+					.getRepositoryConfiguration = getRepositoryConfiguration,
 					.inlineMapping = inlineMapping,
 					.genJoin = genJoin,
 					.genSelect = genSelect,
@@ -199,6 +204,10 @@ fn typedOne(
 	return struct {
 		const Self = @This();
 
+		fn getRepositoryConfiguration(_: *anyopaque) repository.RepositoryConfiguration(ToModel, ToTable) {
+			return toRepositoryConfig;
+		}
+
 		fn inlineMapping(_: *anyopaque) bool {
 			return true;
 		}
@@ -267,11 +276,12 @@ fn typedOne(
 			}
 		}
 
-		pub fn relation(self: *Self) Relation {
+		pub fn relation(self: *Self) Relation(ToModel, ToTable) {
 			return .{
 				._interface = .{
 					.instance = self,
 
+					.getRepositoryConfiguration = getRepositoryConfiguration,
 					.inlineMapping = inlineMapping,
 					.genJoin = genJoin,
 					.genSelect = genSelect,
@@ -282,20 +292,29 @@ fn typedOne(
 	};
 }
 
-
 /// Generic model relation interface.
-pub const Relation = struct {
+pub fn Relation(comptime ToModel: type, comptime ToTable: type) type {
+	return struct {
 		const Self = @This();
 
+		pub const Model = ToModel;
+		pub const TableShape = ToTable;
+
 		_interface: struct {
 			instance: *anyopaque,
 
+			getRepositoryConfiguration: *const fn (self: *anyopaque) repository.RepositoryConfiguration(ToModel, ToTable),
 			inlineMapping: *const fn (self: *anyopaque) bool,
 			genJoin: *const fn (self: *anyopaque, comptime alias: []const u8) []const u8,
 			genSelect: *const fn (self: *anyopaque, comptime table: []const u8, comptime prefix: []const u8) []const u8,
 			buildQuery: *const fn (self: *anyopaque, models: []const anyopaque, query: *anyopaque) anyerror!void,
 		},
 
+		/// Read the related model repository configuration.
+		pub fn getRepositoryConfiguration(self: Self) repository.RepositoryConfiguration(ToModel, ToTable) {
+			return self._interface.getRepositoryConfiguration(self._interface.instance);
+		}
+
 		/// Relation mapping is done inline: this means that it's done at the same time the model is mapped,
 		/// and that the associated data will be retrieved in the main query.
 		pub fn inlineMapping(self: Self) bool {
@@ -317,7 +336,8 @@ pub const Relation = struct {
 		pub fn buildQuery(self: Self, models: []const anyopaque, query: *anyopaque) !void {
 			return self._interface.buildQuery(self._interface.instance, models, query);
 		}
-};
+	};
+}
 
 
 /// A model relation object.

src/result.zig

@@ -3,9 +3,73 @@ const zollections = @import("zollections");
 const _repository = @import("repository.zig");
 const _relations = @import("relations.zig");
 
+/// Type of a retrieved table data, with its retrieved relations.
+pub fn TableWithRelations(comptime TableShape: type, comptime optionalRelations: ?[]const _relations.ModelRelation) type {
+	if (optionalRelations) |relations| {
+		const tableType = @typeInfo(TableShape);
+
+		// Build fields list: copy the existing table type fields and add those for relations.
+		var fields: [tableType.Struct.fields.len + relations.len]std.builtin.Type.StructField = undefined;
+		// Copy base table fields.
+		@memcpy(fields[0..tableType.Struct.fields.len], tableType.Struct.fields);
+
+		// For each relation, create a new struct field in the table shape.
+		for (relations, fields[tableType.Struct.fields.len..]) |relation, *field| {
+			// Get relation field type (optional TableShape of the related value).
+			comptime var relationImpl = relation.relation{};
+			const relationInstanceType = @TypeOf(relationImpl.relation());
+			const relationFieldType = @Type(std.builtin.Type{
+				.Optional = .{
+					.child = relationInstanceType.TableShape
+				},
+			});
+
+			// Create the new field from relation data.
+			field.* = std.builtin.Type.StructField{
+				.name = relation.field ++ [0:0]u8{},
+				.type = relationFieldType,
+				.default_value = null,
+				.is_comptime = false,
+				.alignment = @alignOf(relationFieldType),
+			};
+		}
+
+		// Build the new type.
+		return @Type(std.builtin.Type{
+			.Struct = .{
+				.layout = tableType.Struct.layout,
+				.fields = &fields,
+				.decls = tableType.Struct.decls,
+				.is_tuple = tableType.Struct.is_tuple,
+				.backing_integer = tableType.Struct.backing_integer,
+			},
+		});
+	} else {
+		return TableShape;
+	}
+}
+
+/// Convert a value of the fully retrieved type to the TableShape type.
+pub fn toTableShape(comptime TableShape: type, comptime optionalRelations: ?[]const _relations.ModelRelation, value: TableWithRelations(TableShape, optionalRelations)) TableShape {
+	if (optionalRelations) |_| {
+		// Make a structure of TableShape type.
+		var tableValue: TableShape = undefined;
+
+		// Copy all fields of the table shape in the new structure.
+		inline for (std.meta.fields(TableShape)) |field| {
+			@field(tableValue, field.name) = @field(value, field.name);
+		}
+
+		// Return the simplified structure.
+		return tableValue;
+	} else {
+		// No relations, it should already be of type TableShape.
+		return value;
+	}
+}
+
 /// Generic interface of a query result reader.
 pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[]const _relations.ModelRelation) type {
-	_ = inlineRelations;
 	return struct {
 		const Self = @This();
 
@@ -13,12 +77,12 @@ pub fn QueryResultReader(comptime TableShape: type, comptime inlineRelations: ?[
 		pub const Instance = struct {
 			__interface: struct {
 				instance: *anyopaque,
-				next: *const fn (self: *anyopaque) anyerror!?TableShape, //TODO inline relations.
+				next: *const fn (self: *anyopaque) anyerror!?TableWithRelations(TableShape, inlineRelations),
 			},
 
 			allocator: std.mem.Allocator,
 
-			pub fn next(self: Instance) !?TableShape {
+			pub fn next(self: Instance) !?TableWithRelations(TableShape, inlineRelations) {
 				return self.__interface.next(self.__interface.instance);
 			}
 		};
@@ -55,8 +119,23 @@ pub fn ResultMapper(comptime Model: type, comptime TableShape: type, comptime re
 			while (try reader.next()) |rawModel| {
 				// Parse each raw model from the reader.
 				const model = try allocator.create(Model);
-				model.* = try repositoryConfig.fromSql(rawModel);
+				model.* = try repositoryConfig.fromSql(toTableShape(TableShape, inlineRelations, rawModel));
-				//TODO inline relations.
+
+				// Map inline relations.
+				if (inlineRelations) |_inlineRelations| {
+					// If there are loaded inline relations, map them to the result.
+					inline for (_inlineRelations) |relation| {
+						comptime var relationImpl = relation.relation{};
+						const relationInstance = relationImpl.relation();
+						// Set the read inline relation value.
+						@field(model.*, relation.field) = (
+							if (@field(rawModel, relation.field)) |relationVal|
+								try relationInstance.getRepositoryConfiguration().fromSql(relationVal)
+							else null
+						);
+					}
+				}
+
 				try models.append(model);
 			}