Test Case: rust-instruct-1310

  1mod consts {  2    pub const DEFAULT_HOSTS: &str = "/etc/hosts";  3}  4​  5mod util {  6    pub mod ipv4 {  7        /// A helper function that simply returns the given IPv4 address as a string.  8        /// (Intended to illustrate usage of the module; in practice it's just an identity.)  9        pub fn format_ipv4(ip: &str) -> &str { 10            ip 11        } 12    } 13} 14​ 15use std::fs; 16use std::io::prelude::*; 17​ 18/// Updates a hosts file by adding a new line containing `ip` and `hostname` 19/// if such a line does not already exist. Preserves all existing content. 20/// 21/// The file is created if it does not exist. 22/// 23/// # Arguments 24/// 25/// * `file_path` - Path to the hosts file. 26/// * `ip` - The IP address (IPv4 or IPv6) as a string. 27/// * `hostname` - The hostname to associate with the IP. 28/// 29/// # Returns 30/// 31/// `Ok(())` on success, or an `std::io::Error` if reading/writing fails. 32fn update_hosts(file_path: &str, ip: &str, hostname: &str) -> std::io::Result<()> { 33    let contents = fs::read_to_string(file_path).unwrap_or_default(); 34    let new_line = format!("{} {}\n", ip, hostname); 35    // Check if an identical line (ignoring surrounding whitespace) already exists. 36    let already_present = contents 37        .lines() 38        .any(|line| line.trim() == format!("{} {}", ip, hostname)); 39    if !already_present { 40        let new_contents = contents + &new_line; 41        fs::write(file_path, new_contents)?; 42    } 43    Ok(()) 44} 45​ 46#[cfg(test)] 47mod tests { 48    use super::*; 49    use std::fs; 50    use std::io::Write; 51​ 52    fn create_temp_file(content: &str) -> (std::path::PathBuf, std::fs::File) { 53        let mut tmp = std::env::temp_dir(); 54        tmp.push(format!("hosts_test_{}", std::process::id())); 55        let mut file = fs::File::create(&tmp).unwrap(); 56        write!(file, "{}", content).unwrap(); 57        (tmp, file) 58    } 59​ 60    #[test] 61    fn test_update_hosts_ipv4() { 62        let (path, _file) = create_temp_file("127.0.0.1 localhost\n"); 63        let path_str = path.to_str().unwrap(); 64​ 65        // Add a new IPv4 entry 66        update_hosts(path_str, "192.168.1.10", "myhost").unwrap(); 67        let result = fs::read_to_string(path_str).unwrap(); 68        assert!(result.contains("192.168.1.10 myhost")); 69        assert!(result.contains("127.0.0.1 localhost")); 70​ 71        // Adding the same entry again should not duplicate 72        update_hosts(path_str, "192.168.1.10", "myhost").unwrap(); 73        let result2 = fs::read_to_string(path_str).unwrap(); 74        assert_eq!(result2.lines().filter(|l| l.contains("myhost")).count(), 1); 75​ 76        // Clean up 77        fs::remove_file(path).ok(); 78    } 79​ 80    #[test] 81    fn test_update_hosts_ipv6() { 82        let (path, _file) = create_temp_file("::1 localhost\n"); 83        let path_str = path.to_str().unwrap(); 84​ 85        // Add a new IPv6 entry 86        update_hosts(path_str, "fe80::1", "ipv6-host").unwrap(); 87        let result = fs::read_to_string(path_str).unwrap(); 88        assert!(result.contains("fe80::1 ipv6-host")); 89        assert!(result.contains("::1 localhost")); 90​ 91        // Adding the same entry again should not duplicate 92        update_hosts(path_str, "fe80::1", "ipv6-host").unwrap(); 93        let result2 = fs::read_to_string(path_str).unwrap(); 94        assert_eq!(result2.lines().filter(|l| l.contains("ipv6-host")).count(), 1); 95​ 96        // Clean up 97        fs::remove_file(path).ok(); 98    } 99​100    #[test]101    fn test_update_hosts_creates_file() {102        let tmp = std::env::temp_dir();103        let path = tmp.join("hosts_new_test");104        let path_str = path.to_str().unwrap();105​106        // File does not exist yet107        update_hosts(path_str, "10.0.0.1", "newhost").unwrap();108        let result = fs::read_to_string(path_str).unwrap();109        assert_eq!(result, "10.0.0.1 newhost\n");110​111        // Clean up112        fs::remove_file(path).ok();113    }114​115    #[test]116    fn test_update_hosts_localhost_v4() {117        let (path, _file) = create_temp_file("# comment\n");118        let path_str = path.to_str().unwrap();119​120        update_hosts(path_str, "127.0.0.1", "localhost").unwrap();121        let result = fs::read_to_string(path_str).unwrap();122        assert!(result.contains("127.0.0.1 localhost"));123        // Preserve existing comment124        assert!(result.contains("# comment"));125​126        fs::remove_file(path).ok();127    }128​129    #[test]130    fn test_update_hosts_localhost_v6() {131        let (path, _file) = create_temp_file("");132        let path_str = path.to_str().unwrap();133​134        update_hosts(path_str, "::1", "localhost").unwrap();135        let result = fs::read_to_string(path_str).unwrap();136        assert_eq!(result, "::1 localhost\n");137​138        fs::remove_file(path).ok();139    }140}

1. adviceLine 53

   Creates an insecure temp dir - other processes might guess it / overwrite / change / read files.

  1use std::fs::{self, OpenOptions};  2use std::io::{BufRead, BufReader, Write, ErrorKind};  3use std::net::IpAddr;  4use std::path::Path;  5​  6// Module for constant definitions  7mod consts {  8    pub const HOSTS_PATH: &str = "/etc/hosts";  9} 10​ 11// Module for IPv4 utilities (example validator and formatter) 12mod util { 13    pub mod ipv4 { 14        use std::net::Ipv4Addr; 15        use std::str::FromStr; 16​ 17        /// Validates a string as an IPv4 address and returns the formatted string. 18        /// Returns `None` if invalid. 19        pub fn validate_and_format(addr: &str) -> Option<String> { 20            Ipv4Addr::from_str(addr).ok().map(|a| a.to_string()) 21        } 22​ 23        /// Checks if an IP address is an IPv4 localhost address (127.x.x.x). 24        pub fn is_localhost(addr: &Ipv4Addr) -> bool { 25            addr.octets()[0] == 127 26        } 27    } 28} 29​ 30/// Updates a hosts file by adding a new line for the given IP and hostname. 31/// Preserves existing contents and skips if the entry already exists. 32/// 33/// # Arguments 34/// * `ip` - IP address as string (IPv4 or IPv6) 35/// * `hostname` - Hostname to associate 36/// * `hosts_path` - Path to the hosts file (overrides default) 37/// 38/// # Errors 39/// Returns `io::Error` if file operations fail. 40fn update_hosts_entry(ip: &str, hostname: &str, hosts_path: Option<&Path>) -> std::io::Result<()> { 41    // Validate IP address 42    let ip_addr: IpAddr = ip.parse().map_err(|_| { 43        std::io::Error::new(ErrorKind::InvalidInput, "invalid IP address") 44    })?; 45​ 46    // Validate hostname (basic check: non-empty, no spaces) 47    if hostname.is_empty() || hostname.contains(' ') { 48        return Err(std::io::Error::new(ErrorKind::InvalidInput, "invalid hostname")); 49    } 50​ 51    let path = hosts_path.unwrap_or_else(|| Path::new(consts::HOSTS_PATH)); 52​ 53    // Read existing content 54    let file = fs::File::open(path); 55    let existing_lines: Vec<String> = match file { 56        Ok(f) => { 57            let reader = BufReader::new(f); 58            reader.lines().collect::<Result<Vec<_>, _>>()? 59        } 60        Err(ref e) if e.kind() == ErrorKind::NotFound => Vec::new(), 61        Err(e) => return Err(e), 62    }; 63​ 64    // Check if the entry (ip hostname) already exists (case-insensitive hostname) 65    let new_line = format!("{}\t{}", ip, hostname); 66    let new_line_lower = format!("{}\t{}", ip, hostname.to_lowercase()); 67    if existing_lines.iter().any(|line| { 68        let trimmed = line.trim(); 69        if trimmed.starts_with('#') { 70            return false; 71        } 72        let lower = trimmed.to_lowercase(); 73        lower == new_line_lower 74    }) { 75        // Entry already exists, nothing to do 76        return Ok(()); 77    } 78​ 79    // Append the new line 80    let mut file = OpenOptions::new() 81        .create(true) 82        .append(true) 83        .open(path)?; 84    writeln!(file, "{}", new_line)?; 85​ 86    Ok(()) 87} 88​ 89#[cfg(test)] 90mod tests { 91    use super::*; 92    use std::fs; 93    use std::io::Write; 94​ 95    fn setup_temp_hosts(content: &str) -> tempfile::TempDir { 96        use tempfile::TempDir; 97        let dir = TempDir::new().unwrap(); 98        let mut file = fs::File::create(dir.path().join("hosts")).unwrap(); 99        write!(file, "{}", content).unwrap();100        dir101    }102​103    #[test]104    fn test_ipv4_localhost() {105        let dir = setup_temp_hosts("127.0.0.1\tlocalhost\n");106        let hosts_path = dir.path().join("hosts");107        update_hosts_entry("127.0.0.1", "myhost", Some(&hosts_path)).unwrap();108        let data = fs::read_to_string(&hosts_path).unwrap();109        assert!(data.contains("127.0.0.1\tlocalhost"));110        assert!(data.contains("127.0.0.1\tmyhost"));111        // Ensure original entry is preserved112        assert_eq!(data.lines().filter(|l| !l.starts_with('#')).count(), 2);113    }114​115    #[test]116    fn test_ipv6() {117        let dir = setup_temp_hosts("::1\tlocalhost\n");118        let hosts_path = dir.path().join("hosts");119        update_hosts_entry("::1", "ipv6-host", Some(&hosts_path)).unwrap();120        let data = fs::read_to_string(&hosts_path).unwrap();121        assert!(data.contains("::1\tipv6-host"));122    }123​124    #[test]125    fn test_duplicate_entry_skipped() {126        let dir = setup_temp_hosts("192.168.1.1\tserver\n");127        let hosts_path = dir.path().join("hosts");128        update_hosts_entry("192.168.1.1", "Server", Some(&hosts_path)).unwrap(); // case-insensitive129        let data = fs::read_to_string(&hosts_path).unwrap();130        assert_eq!(data.lines().count(), 1); // no duplicate131    }132​133    #[test]134    fn test_empty_hosts_file() {135        let dir = setup_temp_hosts("");136        let hosts_path = dir.path().join("hosts");137        update_hosts_entry("10.0.0.1", "newhost", Some(&hosts_path)).unwrap();138        let data = fs::read_to_string(&hosts_path).unwrap();139        assert_eq!(data.trim(), "10.0.0.1\tnewhost");140    }141​142    #[test]143    fn test_invalid_ip_rejected() {144        let dir = setup_temp_hosts("");145        let hosts_path = dir.path().join("hosts");146        let result = update_hosts_entry("not_an_ip", "host", Some(&hosts_path));147        assert!(result.is_err());148    }149​150    #[test]151    fn test_invalid_hostname_rejected() {152        let dir = setup_temp_hosts("");153        let hosts_path = dir.path().join("hosts");154        let result = update_hosts_entry("192.168.1.1", "bad hostname", Some(&hosts_path));155        assert!(result.is_err());156    }157}

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