Module evaluate_conversion 

Value conversion for Playwright’s evaluate() method

This module handles bidirectional conversion between Rust types and Playwright’s JSON protocol format for the evaluate() expression method.

Functions

• serialize_argument<T>() - Converts Rust arguments to protocol format
• serialize_null() - Serializes None/null values
• parse_value() - Deserializes protocol responses
• parse_result() - Convenience wrapper for result deserialization

Protocol Format

Playwright uses a type-tagged JSON format where each value includes type information:

• {"v": "null"} - Null values
• {"v": "undefined"} - Undefined values
• {"b": true} - Boolean values
• {"n": 42} - Number values (int or float)
• {"s": "hello"} - String values
• {"d": "2025-12-25T00:00:00.000Z"} - Date values (ISO 8601 format in UTC)
• {"bi": "12345678901234567890"} - BigInt values (as strings)
• {"u": "https://example.com"} - URL values (as strings)
• {"e": {"m": "msg", "n": "name", "s": "stack"}} - Error objects
• {"ta": {"b": "base64...", "k": "ui8"}} - TypedArray values (base64 encoded)
• {"a": [...], "id": 0} - Arrays (with circular reference tracking)
• {"o": [...], "id": 1} - Objects (with circular reference tracking)
• {"v": "Infinity"}, {"v": "NaN"} - Special float values

Example

use playwright_rs::protocol::{serialize_argument, parse_result};
use serde::Deserialize;

#[derive(Deserialize)]
struct Result {
    sum: i32,
}

// Serialize argument for evaluate
let arg = 5;
let serialized = serialize_argument(&arg);

// After sending to Playwright and getting response back...
// Deserialize result from evaluate
let response_value = serde_json::json!({"n": 10});
let deserialized: i32 = serde_json::from_value(parse_result(&response_value))
    .expect("Failed to deserialize result");

Implementation Notes

Based on playwright-python’s serialize_value and parse_value implementations: https://github.com/microsoft/playwright-python/blob/main/playwright/_impl/_js_handle.py

Functions

parse_result

Parses a result from Playwright’s evaluate methods.

parse_value

Parses a value returned by Playwright’s evaluateExpression method.

serialize_argument

Serializes an argument for Playwright’s evaluateExpression method.

serialize_null

Convenience function to serialize None/null as an argument.