Block strings are parsed like non-block strings

[SimonSapin]

Description

Both in the lexer and in the impl From<&'_ ast::StringValue> for String conversion, block strings and "normal" string literals are treated the same except for the number of double-quote delimiters. Block strings should accept different escape sequences (only \"""), remove leading/trailing empty lines, and remove common indent.

https://spec.graphql.org/October2021/#sec-String-Value.Semantics

Steps to reproduce

crates/apollo-parser/src/ast/node_ext.rs

#[cfg(test)]
mod tests {
    use crate::ast;
    use crate::Parser;

    #[test]
    fn test_block_string_1() {
        let input = r#"
            query ($arg: Int!) {
                field(
                    block_string: """
                          other\n\"""

                        \"text\" 
                    """
                )
            }
        "#;
        let values = extract_argument_values(input);
        let ast::Value::StringValue(block_string) = &values[0] else { panic!() };

        // Removed: common indent of non-empty lines, leading/trailing empty lines,
        // but not trailing space of a non-empty line
        // Unescaped: `\"""` only
        assert_eq!(
            String::try_from(block_string).as_deref(),
            Ok(r#"  other\n"""

\"text\" "#)
        );
    }

    #[test]
    fn test_block_string_2() {
        let input = r#"
            query ($arg: Int!) {
                field(
                    block_string: """\""""""
                )
            }
        "#;
        let values = extract_argument_values(input);
        let ast::Value::StringValue(block_string) = &values[0] else { panic!() };
        assert_eq!(String::try_from(block_string).as_deref(), Ok(r#"""""#));
    }

    fn extract_argument_values(input: &str) -> Vec<ast::Value> {
        let ast = Parser::new(input).parse();
        assert_eq!(ast.errors().as_slice(), []);
        let ast::Definition::OperationDefinition(operation) = ast
            .document()
            .definitions()
            .next()
            .unwrap()
        else { panic!("expected an operation") };
        let ast::Selection::Field(field) = operation
            .selection_set()
            .unwrap()
            .selections()
            .next()
            .unwrap()
        else { panic!("expected a field") };
        field
            .arguments()
            .unwrap()
            .arguments()
            .map(|arg| arg.value().unwrap())
            .collect()
    }
}

Expected result

Tests pass

Actual result

---- ast::node_ext::tests::test_block_string_2 stdout ----
thread 'ast::node_ext::tests::test_block_string_2' panicked at 'assertion failed: `(left == right)`
  left: `[ERROR@142:142 "expected R_PAREN, got EOF" EOF, ERROR@142:142 "expected R_CURLY, got EOF" EOF]`,
 right: `[]`', crates/apollo-parser/src/ast/node_ext.rs:333:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

---- ast::node_ext::tests::test_block_string_1 stdout ----
thread 'ast::node_ext::tests::test_block_string_1' panicked at 'assertion failed: `(left == right)`
  left: `Ok("\n                          other\n\"\"\"\n\n                        \"text\" \n                    ")`,
 right: `Ok("  other\\n\"\"\"\n\n\\\"text\\\" ")`', crates/apollo-parser/src/ast/node_ext.rs:309:9

Environment

• apollo-rs crate: apollo-parser
• Crate version: current main, 126816f