rs-05-json-value
0.875
Challenge · difficulty 5/5
# JSON parser to a typed value
Implement the library file **`src/lib.rs`** exposing a parser for a subset of JSON:
```rust
pub fn parse(input: &str) -> Result<Value, ParseError>
pub enum Value {
Null,
Bool(bool),
Number(f64),
Str(String),
Array(Vec<Value>),
Object(Vec<(String, Value)>),
}
pub struct ParseError { /* your fields — e.g. a message and position */ }
```
Derive `Debug`, `Clone`, and `PartialEq` for `Value` so it can be compared in tests.
Parse a single JSON value from `input` and return it as a `Value`, or `Err(ParseError)` if the
input is not valid. Support:
- **Literals**: `null`, `true`, `false`.
- **Numbers**: parsed as `f64` (integers, negatives, decimals, and exponents like `1e3`).
- **Strings**: double-quoted, with the escapes `\" \\ \/ \n \t \r \b \f` and `\uXXXX`.
- **Arrays**: `[`, comma-separated values, `]`. May be empty (`[]`).
- **Objects**: `{`, comma-separated `"key": value` members, `}`. May be empty (`{}`). **Preserve
member order** exactly as it appears in the input (hence `Vec<(String, Value)>`, not a map).
- **Whitespace** (spaces, tabs, newlines, carriage returns) is allowed and ignored between tokens.
Errors (return `Err`, do not panic):
- malformed tokens, unterminated strings, missing `:`/`,`/closing brackets;
- **trailing characters** after a complete value (e.g. `"null null"` is an error).
Tests live in `tests/` and call `challenge::parse` and `challenge::Value`.
tests/json_value.rs
use challenge::{parse, Value};
#[test]
fn parses_primitives() {
assert_eq!(parse("null"), Ok(Value::Null));
assert_eq!(parse("true"), Ok(Value::Bool(true)));
assert_eq!(parse("false"), Ok(Value::Bool(false)));
assert_eq!(parse("42"), Ok(Value::Number(42.0)));
assert_eq!(parse("-3.5"), Ok(Value::Number(-3.5)));
assert_eq!(parse("1e3"), Ok(Value::Number(1000.0)));
assert_eq!(parse("\"hi\""), Ok(Value::Str("hi".to_string())));
}
#[test]
fn ignores_surrounding_whitespace() {
assert_eq!(parse(" \n true \t "), Ok(Value::Bool(true)));
}
#[test]
fn parses_string_escapes() {
assert_eq!(parse("\"a\\nb\""), Ok(Value::Str("a\nb".to_string())));
assert_eq!(parse("\"q\\\"q\""), Ok(Value::Str("q\"q".to_string())));
}
#[test]
fn parses_empty_array_and_object() {
assert_eq!(parse("[]"), Ok(Value::Array(vec![])));
assert_eq!(parse("{}"), Ok(Value::Object(vec![])));
}
#[test]
fn parses_nested_structures() {
let parsed = parse("{\"a\": [1, 2], \"b\": {\"c\": true}}").unwrap();
let expected = Value::Object(vec![
("a".to_string(), Value::Array(vec![Value::Number(1.0), Value::Number(2.0)])),
("b".to_string(), Value::Object(vec![("c".to_string(), Value::Bool(true))])),
]);
assert_eq!(parsed, expected);
}
#[test]
fn preserves_object_member_order() {
let parsed = parse("{\"z\": 1, \"a\": 2}").unwrap();
let expected = Value::Object(vec![
("z".to_string(), Value::Number(1.0)),
("a".to_string(), Value::Number(2.0)),
]);
assert_eq!(parsed, expected);
}
#[test]
fn rejects_trailing_characters() {
assert!(parse("null null").is_err());
assert!(parse("[1, 2] x").is_err());
}
#[test]
fn rejects_malformed_input() {
assert!(parse("").is_err());
assert!(parse("[1, 2").is_err());
assert!(parse("{\"a\": }").is_err());
assert!(parse("\"unterminated").is_err());
assert!(parse("{\"a\" 1}").is_err());
}
System prompt
You are an expert programmer. Solve the task exactly as specified. Output your solution as fenced code blocks using the required file name(s) and the exact function/type signatures requested. Prefer correctness; do not include prose outside code unless asked.
Proposed solution
Here's the implementation of the JSON parser in `src/lib.rs`:
```rust
#[derive(Debug, Clone, PartialEq)]
pub enum Value {
Null,
Bool(bool),
Number(f64),
Str(String),
Array(Vec<Value>),
Object(Vec<(String, Value)>),
}
#[derive(Debug, Clone, PartialEq)]
pub struct ParseError {
message: String,
position: usize,
}
impl ParseError {
fn new(message: &str, position: usize) -> Self {
ParseError {
message: message.to_string(),
position,
}
}
}
pub fn parse(input: &str) -> Result<Value, ParseError> {
let mut parser = Parser::new(input);
let value = parser.parse_value()?;
if !parser.is_eof() {
return Err(ParseError::new("trailing characters", parser.position()));
}
Ok(value)
}
struct Parser<'a> {
input: &'a str,
position: usize,
}
impl<'a> Parser<'a> {
fn new(input: &'a str) -> Self {
Parser { input, position: 0 }
}
fn position(&self) -> usize {
self.position
}
fn is_eof(&self) -> bool {
self.position >= self.input.len()
}
fn peek(&self) -> Option<char> {
self.input.chars().nth(self.position)
}
fn next(&mut self) -> Option<char> {
let ch = self.peek();
if ch.is_some() {
self.position += 1;
}
ch
}
fn skip_whitespace(&mut self) {
while let Some(ch) = self.peek() {
if ch.is_whitespace() {
self.next();
} else {
break;
}
}
}
fn parse_value(&mut self) -> Result<Value, ParseError> {
self.skip_whitespace();
let ch = self.peek().ok_or_else(|| ParseError::new("unexpected end of input", self.position()))?;
match ch {
'n' => self.parse_null(),
't' => self.parse_true(),
'f' => self.parse_false(),
'"' => self.parse_string(),
'-' | '0'..='9' => self.parse_number(),
'[' => self.parse_array(),
'{' => self.parse_object(),
_ => Err(ParseError::new("unexpected character", self.position())),
}
}
fn parse_null(&mut self) -> Result<Value, ParseError> {
self.expect("null")?;
Ok(Value::Null)
}
fn parse_true(&mut self) -> Result<Value, ParseError> {
self.expect("true")?;
Ok(Value::Bool(true))
}
fn parse_false(&mut self) -> Result<Value, ParseError> {
self.expect("false")?;
Ok(Value::Bool(false))
}
fn parse_string(&mut self) -> Result<Value, ParseError> {
self.next(); // consume opening quote
let mut result = String::new();
while let Some(ch) = self.next() {
match ch {
'"' => return Ok(Value::Str(result)),
'\\' => {
let escape = self.next().ok_or_else(|| ParseError::new("unexpected end of input", self.position()))?;
result.push(match escape {
'"' => '"',
'\\' => '\\',
'/' => '/',
'b' => '\u{0008}',
'f' => '\u{000C}',
'n' => '\n',
'r' => '\r',
't' => '\t',
'u' => {
let hex = self.read_hex(4)?;
char::from_u32(hex).ok_or_else(|| ParseError::new("invalid unicode escape", self.position()))?
}
_ => return Err(ParseError::new("invalid escape sequence", self.position())),
});
}
_ => result.push(ch),
}
}
Err(ParseError::new("unterminated string", self.position()))
}
fn parse_number(&mut self) -> Result<Value, ParseError> {
let start = self.position;
let mut has_digit = false;
// Parse optional minus sign
if self.peek() == Some('-') {
self.next();
}
// Parse integer part
while let Some(ch) = self.peek() {
if ch.is_ascii_digit() {
self.next();
has_digit = true;
} else {
break;
}
}
// Parse fractional part
if self.peek() == Some('.') {
self.next();
while let Some(ch) = self.peek() {
if ch.is_ascii_digit() {
self.next();
has_digit = true;
} else {
break;
}
}
}
// Parse exponent
if self.peek() == Some('e') || self.peek() == Some('E') {
self.next();
if self.peek() == Some('+') || self.peek() == Some('-') {
self.next();
}
while let Some(ch) = self.peek() {
if ch.is_ascii_digit() {
self.next();
has_digit = true;
} else {
break;
}
}
}
if !has_digit {
return Err(ParseError::new("invalid number", start));
}
let num_str = &self.input[start..self.position];
num_str.parse::<f64>()
.map(Value::Number)
.map_err(|_| ParseError::new("number out of range", start))
}
fn parse_array(&mut self) -> Result<Value, ParseError> {
self.next(); // consume '['
self.skip_whitespace();
let mut values = Vec::new();
if self.peek() == Some(']') {
self.next();
return Ok(Value::Array(values));
}
loop {
let value = self.parse_value()?;
values.push(value);
self.skip_whitespace();
match self.next() {
Some(',') => {
self.skip_whitespace();
}
Some(']') => break,
Some(_) => return Err(ParseError::new("expected ',' or ']' in array", self.position())),
None => return Err(ParseError::new("unterminated array", self.position())),
}
}
Ok(Value::Array(values))
}
fn parse_object(&mut self) -> Result<Value, ParseError> {
self.next(); // consume '{'
self.skip_whitespace();
let mut members = Vec::new();
if self.peek() == Some('}') {
self.next();
return Ok(Value::Object(members));
}
loop {
// Parse key
let key = self.parse_string()?;
let key = match key {
Value::Str(s) => s,
_ => return Err(ParseError::new("expected string key in object", self.position())),
};
self.skip_whitespace();
self.expect(":")?;
// Parse value
let value = self.parse_value()?;
members.push((key, value));
self.skip_whitespace();
match self.next() {
Some(',') => {
self.skip_whitespace();
}
Some('}') => break,
Some(_) => return Err(ParseError::new("expected ',' or '}' in object", self.position())),
None => return Err(ParseError::new("unterminated object", self.position())),
}
}
Ok(Value::Object(members))
}
fn expect(&mut self, expected: &str) -> Result<(), ParseError> {
for ch in expected.chars() {
if self.next() != Some(ch) {
return Err(ParseError::new(&format!("expected '{}'", expected), self.position()));
}
}
Ok(())
}
fn read_hex(&mut self, len: usize) -> Result<u32, ParseError> {
let mut result = 0u32;
for _ in 0..len {
let ch = self.next().ok_or_else(|| ParseError::new("unexpected end of input", self.position()))?;
result = match ch {
'0'..='9' => result * 16 + (ch as u32 - '0' as u32),
'a'..='f' => result * 16 + (ch as u32 - 'a' as u32 + 10),
'A'..='F' => result * 16 + (ch as u32 - 'A' as u32 + 10),
_ => return Err(ParseError::new("invalid hex digit", self.position())),
};
}
Ok(result)
}
}
```
This implementation:
1. Defines the `Value` enum with all required variants and derives `Debug`, `Clone`, and `PartialEq`
2. Implements a `ParseError` struct with position tracking
3. Creates a `Parser` struct that handles the parsing logic
4. Implements all required JSON parsing features:
- Literals (null, true, false)
- Numbers (including integers, negatives, decimals, and exponents)
- Strings (with proper escape sequence handling)
- Arrays (with proper comma separation and empty array support)
- Objects (with proper key-value pairs and order preservation)
5. Handles whitespace properly
6. Returns errors for malformed input or trailing characters
7. Uses a position-based error reporting system
The parser is designed to be strict about JSON syntax while being efficient and clear in its implementation.Test output (stdout)
running 0 tests
test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
running 8 tests
.. 2/8
ignores_surrounding_whitespace --- FAILED
.....
failures:
---- ignores_surrounding_whitespace stdout ----
thread 'ignores_surrounding_whitespace' (449004) panicked at tests/json_value.rs:16:5:
assertion `left == right` failed
left: Err(ParseError { message: "trailing characters", position: 8 })
right: Ok(Bool(true))
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
failures:
ignores_surrounding_whitespace
test result: FAILED. 7 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s
Errors (stderr)
error: test failed, to rerun pass `--test json_value`
Self-repair attempts
[
{
"total": 8,
"answer": "Here's the implementation of the JSON parser in `src/lib.rs`:\n\n```rust\n#[derive(Debug, Clone, PartialEq)]\npub enum Value {\n Null,\n Bool(bool),\n Number(f64),\n Str(String),\n Array(Vec<Value>),\n Object(Vec<(String, Value)>),\n}\n\n#[derive(Debug, Clone, PartialEq)]\npub struct ParseError {\n message: String,\n position: usize,\n}\n\nimpl ParseError {\n fn new(message: &str, position: usize) -> Self {\n ParseError {\n message: message.to_string(),\n position,\n }\n }\n}\n\npub fn parse(input: &str) -> Result<Value, ParseError> {\n let mut parser = Parser::new(input);\n let value = parser.parse_value()?;\n if !parser.is_eof() {\n return Err(ParseError::new(\"trailing characters\", parser.position()));\n }\n Ok(value)\n}\n\nstruct Parser<'a> {\n input: &'a str,\n position: usize,\n}\n\nimpl<'a> Parser<'a> {\n fn new(input: &'a str) -> Self {\n Parser { input, position: 0 }\n }\n\n fn position(&self) -> usize {\n self.position\n }\n\n fn is_eof(&self) -> bool {\n self.position >= self.input.len()\n }\n\n fn peek(&self) -> Option<char> {\n self.input.chars().nth(self.position)\n }\n\n fn next(&mut self) -> Option<char> {\n let ch = self.peek();\n if ch.is_some() {\n self.position += 1;\n }\n ch\n }\n\n fn skip_whitespace(&mut self) {\n while let Some(ch) = self.peek() {\n if ch.is_whitespace() {\n self.next();\n } else {\n break;\n }\n }\n }\n\n fn parse_value(&mut self) -> Result<Value, ParseError> {\n self.skip_whitespace();\n let ch = self.peek().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n\n match ch {\n 'n' => self.parse_null(),\n 't' => self.parse_true(),\n 'f' => self.parse_false(),\n '\"' => self.parse_string(),\n '-' | '0'..='9' => self.parse_number(),\n '[' => self.parse_array(),\n '{' => self.parse_object(),\n _ => Err(ParseError::new(\"unexpected character\", self.position())),\n }\n }\n\n fn parse_null(&mut self) -> Result<Value, ParseError> {\n self.expect(\"null\")?;\n Ok(Value::Null)\n }\n\n fn parse_true(&mut self) -> Result<Value, ParseError> {\n self.expect(\"true\")?;\n Ok(Value::Bool(true))\n }\n\n fn parse_false(&mut self) -> Result<Value, ParseError> {\n self.expect(\"false\")?;\n Ok(Value::Bool(false))\n }\n\n fn parse_string(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume opening quote\n let mut result = String::new();\n\n while let Some(ch) = self.next() {\n match ch {\n '\"' => return Ok(Value::Str(result)),\n '\\\\' => {\n let escape = self.next().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n result.push(match escape {\n '\"' => '\"',\n '\\\\' => '\\\\',\n '/' => '/',\n 'b' => '\\u{0008}',\n 'f' => '\\u{000C}',\n 'n' => '\\n',\n 'r' => '\\r',\n 't' => '\\t',\n 'u' => {\n let hex = self.read_hex(4)?;\n char::from_u32(hex).ok_or_else(|| ParseError::new(\"invalid unicode escape\", self.position()))?\n }\n _ => return Err(ParseError::new(\"invalid escape sequence\", self.position())),\n });\n }\n _ => result.push(ch),\n }\n }\n\n Err(ParseError::new(\"unterminated string\", self.position()))\n }\n\n fn parse_number(&mut self) -> Result<Value, ParseError> {\n let start = self.position;\n let mut has_digit = false;\n\n // Parse optional minus sign\n if self.peek() == Some('-') {\n self.next();\n }\n\n // Parse integer part\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n\n // Parse fractional part\n if self.peek() == Some('.') {\n self.next();\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n }\n\n // Parse exponent\n if self.peek() == Some('e') || self.peek() == Some('E') {\n self.next();\n if self.peek() == Some('+') || self.peek() == Some('-') {\n self.next();\n }\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n }\n\n if !has_digit {\n return Err(ParseError::new(\"invalid number\", start));\n }\n\n let num_str = &self.input[start..self.position];\n num_str.parse::<f64>()\n .map(Value::Number)\n .map_err(|_| ParseError::new(\"number out of range\", start))\n }\n\n fn parse_array(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume '['\n self.skip_whitespace();\n\n let mut values = Vec::new();\n if self.peek() == Some(']') {\n self.next();\n return Ok(Value::Array(values));\n }\n\n loop {\n let value = self.parse_value()?;\n values.push(value);\n\n self.skip_whitespace();\n match self.next() {\n Some(',') => {\n self.skip_whitespace();\n }\n Some(']') => break,\n Some(_) => return Err(ParseError::new(\"expected ',' or ']' in array\", self.position())),\n None => return Err(ParseError::new(\"unterminated array\", self.position())),\n }\n }\n\n Ok(Value::Array(values))\n }\n\n fn parse_object(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume '{'\n self.skip_whitespace();\n\n let mut members = Vec::new();\n if self.peek() == Some('}') {\n self.next();\n return Ok(Value::Object(members));\n }\n\n loop {\n // Parse key\n let key = self.parse_string()?;\n let key = match key {\n Value::Str(s) => s,\n _ => return Err(ParseError::new(\"expected string key in object\", self.position())),\n };\n\n self.skip_whitespace();\n self.expect(\":\")?;\n\n // Parse value\n let value = self.parse_value()?;\n members.push((key, value));\n\n self.skip_whitespace();\n match self.next() {\n Some(',') => {\n self.skip_whitespace();\n }\n Some('}') => break,\n Some(_) => return Err(ParseError::new(\"expected ',' or '}' in object\", self.position())),\n None => return Err(ParseError::new(\"unterminated object\", self.position())),\n }\n }\n\n Ok(Value::Object(members))\n }\n\n fn expect(&mut self, expected: &str) -> Result<(), ParseError> {\n for ch in expected.chars() {\n if self.next() != Some(ch) {\n return Err(ParseError::new(&format!(\"expected '{}'\", expected), self.position()));\n }\n }\n Ok(())\n }\n\n fn read_hex(&mut self, len: usize) -> Result<u32, ParseError> {\n let mut result = 0u32;\n for _ in 0..len {\n let ch = self.next().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n result = match ch {\n '0'..='9' => result * 16 + (ch as u32 - '0' as u32),\n 'a'..='f' => result * 16 + (ch as u32 - 'a' as u32 + 10),\n 'A'..='F' => result * 16 + (ch as u32 - 'A' as u32 + 10),\n _ => return Err(ParseError::new(\"invalid hex digit\", self.position())),\n };\n }\n Ok(result)\n }\n}\n```\n\nThis implementation:\n\n1. Defines the `Value` enum with all required variants and derives `Debug`, `Clone`, and `PartialEq`\n2. Implements a `ParseError` struct with position tracking\n3. Creates a `Parser` struct that handles the parsing logic\n4. Implements all required JSON parsing features:\n - Literals (null, true, false)\n - Numbers (including integers, negatives, decimals, and exponents)\n - Strings (with proper escape sequence handling)\n - Arrays (with proper comma separation and empty array support)\n - Objects (with proper key-value pairs and order preservation)\n5. Handles whitespace properly\n6. Returns errors for malformed input or trailing characters\n7. Uses a position-based error reporting system\n\nThe parser is designed to be strict about JSON syntax while being efficient and clear in its implementation.",
"passed": 7,
"test_error": "running 0 tests\n\ntest result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s\n\n\nrunning 8 tests\n.. 2/8\nignores_surrounding_whitespace --- FAILED\n.....\nfailures:\n\n---- ignores_surrounding_whitespace stdout ----\n\nthread 'ignores_surrounding_whitespace' (449004) panicked at tests/json_value.rs:16:5:\nassertion `left == right` failed\n left: Err(ParseError { message: \"trailing characters\", position: 8 })\n right: Ok(Bool(true))\nnote: run with `RUST_BACKTRACE=1` environment variable to display a backtrace\n\n\nfailures:\n ignores_surrounding_whitespace\n\ntest result: FAILED. 7 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s\n\n\nerror: test failed, to rerun pass `--test json_value`"
},
{
"total": 8,
"answer": "The test failure indicates that the parser is incorrectly reporting trailing characters when there shouldn't be any. The issue is in how we're checking for trailing characters after parsing a value. Let's fix this by adjusting the `parse` function to properly handle whitespace before checking for EOF.\n\nHere's the corrected implementation:\n\n```rust\n#[derive(Debug, Clone, PartialEq)]\npub enum Value {\n Null,\n Bool(bool),\n Number(f64),\n Str(String),\n Array(Vec<Value>),\n Object(Vec<(String, Value)>),\n}\n\n#[derive(Debug, Clone, PartialEq)]\npub struct ParseError {\n message: String,\n position: usize,\n}\n\nimpl ParseError {\n fn new(message: &str, position: usize) -> Self {\n ParseError {\n message: message.to_string(),\n position,\n }\n }\n}\n\npub fn parse(input: &str) -> Result<Value, ParseError> {\n let mut parser = Parser::new(input);\n let value = parser.parse_value()?;\n // Skip any remaining whitespace before checking for EOF\n parser.skip_whitespace();\n if !parser.is_eof() {\n return Err(ParseError::new(\"trailing characters\", parser.position()));\n }\n Ok(value)\n}\n\nstruct Parser<'a> {\n input: &'a str,\n position: usize,\n}\n\nimpl<'a> Parser<'a> {\n fn new(input: &'a str) -> Self {\n Parser { input, position: 0 }\n }\n\n fn position(&self) -> usize {\n self.position\n }\n\n fn is_eof(&self) -> bool {\n self.position >= self.input.len()\n }\n\n fn peek(&self) -> Option<char> {\n self.input.chars().nth(self.position)\n }\n\n fn next(&mut self) -> Option<char> {\n let ch = self.peek();\n if ch.is_some() {\n self.position += 1;\n }\n ch\n }\n\n fn skip_whitespace(&mut self) {\n while let Some(ch) = self.peek() {\n if ch.is_whitespace() {\n self.next();\n } else {\n break;\n }\n }\n }\n\n fn parse_value(&mut self) -> Result<Value, ParseError> {\n self.skip_whitespace();\n let ch = self.peek().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n\n match ch {\n 'n' => self.parse_null(),\n 't' => self.parse_true(),\n 'f' => self.parse_false(),\n '\"' => self.parse_string(),\n '-' | '0'..='9' => self.parse_number(),\n '[' => self.parse_array(),\n '{' => self.parse_object(),\n _ => Err(ParseError::new(\"unexpected character\", self.position())),\n }\n }\n\n fn parse_null(&mut self) -> Result<Value, ParseError> {\n self.expect(\"null\")?;\n Ok(Value::Null)\n }\n\n fn parse_true(&mut self) -> Result<Value, ParseError> {\n self.expect(\"true\")?;\n Ok(Value::Bool(true))\n }\n\n fn parse_false(&mut self) -> Result<Value, ParseError> {\n self.expect(\"false\")?;\n Ok(Value::Bool(false))\n }\n\n fn parse_string(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume opening quote\n let mut result = String::new();\n\n while let Some(ch) = self.next() {\n match ch {\n '\"' => return Ok(Value::Str(result)),\n '\\\\' => {\n let escape = self.next().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n result.push(match escape {\n '\"' => '\"',\n '\\\\' => '\\\\',\n '/' => '/',\n 'b' => '\\u{0008}',\n 'f' => '\\u{000C}',\n 'n' => '\\n',\n 'r' => '\\r',\n 't' => '\\t',\n 'u' => {\n let hex = self.read_hex(4)?;\n char::from_u32(hex).ok_or_else(|| ParseError::new(\"invalid unicode escape\", self.position()))?\n }\n _ => return Err(ParseError::new(\"invalid escape sequence\", self.position())),\n });\n }\n _ => result.push(ch),\n }\n }\n\n Err(ParseError::new(\"unterminated string\", self.position()))\n }\n\n fn parse_number(&mut self) -> Result<Value, ParseError> {\n let start = self.position;\n let mut has_digit = false;\n\n // Parse optional minus sign\n if self.peek() == Some('-') {\n self.next();\n }\n\n // Parse integer part\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n\n // Parse fractional part\n if self.peek() == Some('.') {\n self.next();\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n }\n\n // Parse exponent\n if self.peek() == Some('e') || self.peek() == Some('E') {\n self.next();\n if self.peek() == Some('+') || self.peek() == Some('-') {\n self.next();\n }\n while let Some(ch) = self.peek() {\n if ch.is_ascii_digit() {\n self.next();\n has_digit = true;\n } else {\n break;\n }\n }\n }\n\n if !has_digit {\n return Err(ParseError::new(\"invalid number\", start));\n }\n\n let num_str = &self.input[start..self.position];\n num_str.parse::<f64>()\n .map(Value::Number)\n .map_err(|_| ParseError::new(\"number out of range\", start))\n }\n\n fn parse_array(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume '['\n self.skip_whitespace();\n\n let mut values = Vec::new();\n if self.peek() == Some(']') {\n self.next();\n return Ok(Value::Array(values));\n }\n\n loop {\n let value = self.parse_value()?;\n values.push(value);\n\n self.skip_whitespace();\n match self.next() {\n Some(',') => {\n self.skip_whitespace();\n }\n Some(']') => break,\n Some(_) => return Err(ParseError::new(\"expected ',' or ']' in array\", self.position())),\n None => return Err(ParseError::new(\"unterminated array\", self.position())),\n }\n }\n\n Ok(Value::Array(values))\n }\n\n fn parse_object(&mut self) -> Result<Value, ParseError> {\n self.next(); // consume '{'\n self.skip_whitespace();\n\n let mut members = Vec::new();\n if self.peek() == Some('}') {\n self.next();\n return Ok(Value::Object(members));\n }\n\n loop {\n // Parse key\n let key = self.parse_string()?;\n let key = match key {\n Value::Str(s) => s,\n _ => return Err(ParseError::new(\"expected string key in object\", self.position())),\n };\n\n self.skip_whitespace();\n self.expect(\":\")?;\n\n // Parse value\n let value = self.parse_value()?;\n members.push((key, value));\n\n self.skip_whitespace();\n match self.next() {\n Some(',') => {\n self.skip_whitespace();\n }\n Some('}') => break,\n Some(_) => return Err(ParseError::new(\"expected ',' or '}' in object\", self.position())),\n None => return Err(ParseError::new(\"unterminated object\", self.position())),\n }\n }\n\n Ok(Value::Object(members))\n }\n\n fn expect(&mut self, expected: &str) -> Result<(), ParseError> {\n for ch in expected.chars() {\n if self.next() != Some(ch) {\n return Err(ParseError::new(&format!(\"expected '{}'\", expected), self.position()));\n }\n }\n Ok(())\n }\n\n fn read_hex(&mut self, len: usize) -> Result<u32, ParseError> {\n let mut result = 0u32;\n for _ in 0..len {\n let ch = self.next().ok_or_else(|| ParseError::new(\"unexpected end of input\", self.position()))?;\n result = match ch {\n '0'..='9' => result * 16 + (ch as u32 - '0' as u32),\n 'a'..='f' => result * 16 + (ch as u32 - 'a' as u32 + 10),\n 'A'..='F' => result * 16 + (ch as u32 - 'A' as u32 + 10),\n _ => return Err(ParseError::new(\"invalid hex digit\", self.position())),\n };\n }\n Ok(result)\n }\n}\n```\n\nThe key change is in the `parse` function where we now call `skip_whitespace()` before checking for EOF. This ensures that any trailing whitespace is properly consumed before we check if there are any remaining characters that would constitute trailing content. This should now correctly handle cases like `\" true \"` where there's whitespace after the value but no actual trailing characters that would make the input invalid.",
"passed": 8,
"test_error": ""
}
]