doc tests

lib/std/json.zig

@@ -1,14 +1,70 @@
 //! JSON parsing and stringification conforming to RFC 8259. https://datatracker.ietf.org/doc/html/rfc8259
 //!
-//! The low-level `Scanner` API reads from an input slice or successive slices of inputs,
+//! The low-level `Scanner` API produces `Token`s from an input slice or successive slices of inputs,
 //! The `Reader` API connects a `std.io.Reader` to a `Scanner`.
 //!
-//! The high-level `parseFromSlice` and `parseFromTokenSource` deserializes a JSON document into a Zig type.
+//! The high-level `parseFromSlice` and `parseFromTokenSource` deserialize a JSON document into a Zig type.
 //! Parse into a dynamically-typed `Value` to load any JSON value for runtime inspection.
 //!
 //! The low-level `writeStream` emits syntax-conformant JSON tokens to a `std.io.Writer`.
 //! The high-level `stringify` serializes a Zig or `Value` type into JSON.
 
+const testing = @import("std").testing;
+const ArrayList = @import("std").ArrayList;
+
+test Scanner {
+    var scanner = Scanner.initCompleteInput(testing.allocator, "{\"foo\": 123}\n");
+    defer scanner.deinit();
+    try testing.expectEqual(Token.object_begin, try scanner.next());
+    try testing.expectEqualSlices(u8, "foo", (try scanner.next()).string);
+    try testing.expectEqualSlices(u8, "123", (try scanner.next()).number);
+    try testing.expectEqual(Token.object_end, try scanner.next());
+    try testing.expectEqual(Token.end_of_document, try scanner.next());
+}
+
+test parseFromSlice {
+    var parsed_str = try parseFromSlice([]const u8, testing.allocator, "\"a\\u0020b\"", .{});
+    defer parsed_str.deinit();
+    try testing.expectEqualSlices(u8, "a b", parsed_str.value);
+
+    const T = struct { a: i32 = -1, b: [2]u8 };
+    var parsed_struct = try parseFromSlice(T, testing.allocator, "{\"b\":\"xy\"}", .{});
+    defer parsed_struct.deinit();
+    try testing.expectEqual(@as(i32, -1), parsed_struct.value.a); // default value
+    try testing.expectEqualSlices(u8, "xy", parsed_struct.value.b[0..]);
+}
+
+test Value {
+    var parsed = try parseFromSlice(Value, testing.allocator, "{\"anything\": \"goes\"}", .{});
+    defer parsed.deinit();
+    try testing.expectEqualSlices(u8, "goes", parsed.value.object.get("anything").?.string);
+}
+
+test writeStream {
+    var out = ArrayList(u8).init(testing.allocator);
+    defer out.deinit();
+    var write_stream = writeStream(out.writer(), 99);
+    try write_stream.beginObject();
+    try write_stream.objectField("foo");
+    try write_stream.emitNumber(123);
+    try write_stream.endObject();
+    const expected =
+        \\{
+        \\ "foo": 123
+        \\}
+    ;
+    try testing.expectEqualSlices(u8, expected, out.items);
+}
+
+test stringify {
+    var out = ArrayList(u8).init(testing.allocator);
+    defer out.deinit();
+
+    const T = struct { a: i32, b: []const u8 };
+    try stringify(T{ .a = 123, .b = "xy" }, .{}, out.writer());
+    try testing.expectEqualSlices(u8, "{\"a\":123,\"b\":\"xy\"}", out.items);
+}
+
 pub const ObjectMap = @import("json/dynamic.zig").ObjectMap;
 pub const Array = @import("json/dynamic.zig").Array;
 pub const Value = @import("json/dynamic.zig").Value;