mini-static 0.38.5

A secure, async static file server with streaming, traversal protection, and connection limits.
Documentation
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use mini_static::Server;
use std::fs;
use std::time::Duration;
use tempfile::TempDir;
use tokio::io::{AsyncReadExt, AsyncWriteExt};
use tokio::net::TcpStream;

#[test]
fn server_new_canonicalizes_root() {
    let root = TempDir::new().unwrap();
    let result = Server::new(root.path());
    assert!(
        result.is_ok(),
        "Server::new should succeed with a valid root"
    );
}

#[test]
fn server_new_fails_with_invalid_root() {
    let result = Server::new(std::path::Path::new(
        "/nonexistent/path/that/does/not/exist",
    ));
    assert!(result.is_err(), "Server::new should fail with invalid root");
}

#[test]
fn server_multiple_resolves_without_root_recanonical() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("file1.txt"), b"content1").unwrap();
    fs::write(root.path().join("file2.txt"), b"content2").unwrap();

    let server = Server::new(root.path()).unwrap();

    // Multiple resolve calls should all work
    let res1 = server.resolve("/file1.txt");
    let res2 = server.resolve("/file2.txt");
    let res3 = server.resolve("/file1.txt");

    assert!(res1.is_ok());
    assert!(res2.is_ok());
    assert!(res3.is_ok());
}

#[test]
fn server_rejects_traversal_on_multiple_requests() {
    let root = TempDir::new().unwrap();

    let server = Server::new(root.path()).unwrap();

    // Multiple traversal attempts should all be rejected
    let res1 = server.resolve("/../etc/passwd");
    let res2 = server.resolve("/../../etc/passwd");
    let res3 = server.resolve("/../etc/passwd");

    assert!(res1.is_err());
    assert!(res2.is_err());
    assert!(res3.is_err());
}

// The 404 responses for a missing file and for a traversal attempt are covered in
// `http_responses.rs`, which additionally asserts the two are byte-identical.

#[test]
fn server_resolve_with_canonical_root_direct() {
    let root = TempDir::new().unwrap();
    let test_file = root.path().join("test.txt");
    fs::write(&test_file, b"content").unwrap();

    let root_canon = root.path().canonicalize().unwrap();
    let result = mini_static::resolve_with_canonical_root(&root_canon, "/test.txt");

    assert!(result.is_ok());
}

#[test]
fn server_multiple_requests_same_effectiveness() {
    let root = TempDir::new().unwrap();
    fs::create_dir(root.path().join("subdir")).unwrap();
    fs::write(root.path().join("subdir/index.html"), b"<html></html>").unwrap();
    fs::write(root.path().join("file.txt"), b"content").unwrap();

    let server = Server::new(root.path()).unwrap();

    // Multiple different types of requests
    let dir_with_index = server.resolve("/subdir");
    let file = server.resolve("/file.txt");
    let missing = server.resolve("/missing.txt");
    let traversal = server.resolve("/../etc/passwd");

    assert!(
        dir_with_index.is_ok(),
        "directory with index should resolve"
    );
    assert!(file.is_ok(), "regular file should resolve");
    assert!(missing.is_err(), "missing file should error");
    assert!(traversal.is_err(), "traversal should error");
}

#[tokio::test]
async fn server_header_read_timeout_closes_idle_connection() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"hello world").unwrap();

    let server = Server::new(root.path()).unwrap();
    let header_timeout = Duration::from_millis(100);
    let (port, _handle) = server.run(header_timeout).await.unwrap();

    // Give the server a moment to start listening
    tokio::time::sleep(Duration::from_millis(10)).await;

    // Connect but send nothing - connection should timeout
    let addr = format!("127.0.0.1:{}", port);
    let mut stream = TcpStream::connect(&addr).await.unwrap();

    // Wait longer than the timeout
    tokio::time::sleep(Duration::from_millis(200)).await;

    // Try to read from the closed connection - should return empty (EOF)
    let mut buf = vec![0u8; 1024];
    match stream.read(&mut buf).await {
        Ok(n) => assert_eq!(n, 0, "read from timed-out connection should return EOF"),
        Err(e) => panic!("read from timed-out connection failed: {}", e),
    }

    // Verify a new connection still works
    let mut new_stream = TcpStream::connect(&addr).await.unwrap();
    new_stream
        .write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();

    let mut buf = vec![0u8; 1024];
    let n = new_stream.read(&mut buf).await.unwrap();
    let response = String::from_utf8_lossy(&buf[..n]);

    assert!(
        response.contains("HTTP/1.1 200"),
        "new connection should work and return 200, got: {}",
        response
    );
}

#[tokio::test]
async fn server_run_ephemeral_binds_to_loopback() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("index.html"), b"<html>hello</html>").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, _handle) = server.run_ephemeral().await.unwrap();

    // Give the server a moment to start listening
    tokio::time::sleep(Duration::from_millis(10)).await;

    // Verify we can connect to 127.0.0.1:port
    let addr = format!("127.0.0.1:{}", port);
    let mut stream = TcpStream::connect(&addr).await.unwrap();

    // Send a valid HTTP request
    stream
        .write_all(b"GET /index.html HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();

    // Read to EOF rather than a single `read()`: the body now streams as its own
    // frame(s) separate from the header write, so a single `read()` can legitimately
    // return only the headers if the body frame hasn't been flushed yet.
    let mut response_data = Vec::new();
    stream.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "run_ephemeral should be accessible on loopback, got: {}",
        response
    );
    assert!(
        response.contains("hello"),
        "response should contain file content, got: {}",
        response
    );
}

#[tokio::test]
async fn server_streams_large_files_efficiently() {
    let root = TempDir::new().unwrap();

    // Create a 1MB test file with predictable content
    let large_content = vec![42u8; 1024 * 1024];
    fs::write(root.path().join("large.bin"), &large_content).unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, _handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;

    // Request the large file
    let addr = format!("127.0.0.1:{}", port);
    let mut stream = TcpStream::connect(&addr).await.unwrap();

    stream
        .write_all(b"GET /large.bin HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();

    // Read the entire response
    let mut response_data = Vec::new();
    stream.read_to_end(&mut response_data).await.unwrap();

    let response_str = String::from_utf8_lossy(&response_data);

    // Verify the response headers are correct
    let header_part = response_str.split("\r\n\r\n").next().unwrap_or("");
    let headers_lowercase = header_part.to_lowercase();

    assert!(
        response_str.contains("HTTP/1.1 200"),
        "should return 200 OK"
    );
    assert!(
        headers_lowercase.contains("content-length: 1048576"),
        "Content-Length should be exactly 1MB, got headers: {}",
        header_part
    );

    // Verify the file content is correct
    // The body starts after the double CRLF in the headers
    if let Some(body_start) = response_data.windows(4).position(|w| w == b"\r\n\r\n") {
        let body = &response_data[body_start + 4..];
        assert_eq!(body.len(), 1048576, "body should be exactly 1MB");
        assert!(
            body.iter().all(|&b| b == 42),
            "file content should be preserved through streaming"
        );
    } else {
        panic!("could not find body separator in response");
    }
}

#[tokio::test]
async fn server_serves_non_ascii_filenames() {
    let root = TempDir::new().unwrap();

    // Create files with non-ASCII characters in their names
    // Using UTF-8 filenames directly (supported on modern filesystems)
    let filename = "café.txt";
    let content = "hello from café";
    fs::write(root.path().join(filename), content).unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, _handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;

    let addr = format!("127.0.0.1:{}", port);

    // Request the file using percent-encoded UTF-8 path
    // "café" in UTF-8 bytes: c3 a9 (for é) encoded as %C3%A9
    // So "café" becomes "caf%C3%A9"
    let encoded_path = "/caf%C3%A9.txt".to_string();
    let request = format!(
        "GET {} HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n",
        encoded_path
    );

    let mut stream = TcpStream::connect(&addr).await.unwrap();
    stream.write_all(request.as_bytes()).await.unwrap();

    let mut response_data = Vec::new();
    stream.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "non-ASCII filename should resolve correctly, got: {}",
        response
    );
    assert!(
        response.contains("hello from café"),
        "response should contain file content with non-ASCII chars"
    );
}

#[tokio::test]
async fn server_non_ascii_filenames_still_block_traversal() {
    let root = TempDir::new().unwrap();
    let subdir = root.path().join("subdir");
    fs::create_dir(&subdir).unwrap();

    // Create a file outside the allowed directory
    fs::write(root.path().join("secret.txt"), b"secret").unwrap();

    // Create a file in the subdirectory
    fs::write(subdir.join("public.txt"), b"public").unwrap();

    let server = Server::new(&subdir).unwrap();
    let (port, _handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;

    let addr = format!("127.0.0.1:{}", port);

    // Try to traverse up and access the secret file with various encodings
    // Including percent-encoded "../" sequences
    let traversal_attempts = vec![
        "/../secret.txt",     // Direct traversal
        "/%2E%2E/secret.txt", // Percent-encoded ".." should still be blocked at segment level
    ];

    for attempt in traversal_attempts {
        let request = format!(
            "GET {} HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n",
            attempt
        );

        let mut stream = TcpStream::connect(&addr).await.unwrap();
        stream.write_all(request.as_bytes()).await.unwrap();

        let mut response_data = Vec::new();
        stream.read_to_end(&mut response_data).await.unwrap();
        let response = String::from_utf8_lossy(&response_data);

        assert!(
            response.contains("HTTP/1.1 404"),
            "traversal attempt {} should return 404, got: {}",
            attempt,
            response
        );
        assert!(
            !response.contains("secret"),
            "traversal attempt {} should not leak file content",
            attempt
        );
    }
}

#[tokio::test]
async fn server_with_max_connections_bounds_concurrent_connections() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"content").unwrap();

    // With a limit of exactly 1, a second connection's request must wait for the
    // first connection's slot to free up rather than being served concurrently.
    let header_timeout = Duration::from_millis(150);
    let server = Server::new(root.path()).unwrap().with_max_connections(1);
    let (port, _handle) = server.run(header_timeout).await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // Connection A: opens a socket and sends nothing, occupying the single
    // connection slot until header_timeout closes it.
    let _blocking_conn = TcpStream::connect(&addr).await.unwrap();

    // Connection B: sends a real request while A still holds the only slot.
    let mut conn_b = TcpStream::connect(&addr).await.unwrap();
    conn_b
        .write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();

    // B must not be served yet: with no connection limit, the accept loop would
    // have spawned B's handler immediately regardless of A. A short read timeout
    // here would fail (return data) if the limit weren't being enforced.
    let mut buf = vec![0u8; 1024];
    let early_read = tokio::time::timeout(Duration::from_millis(60), conn_b.read(&mut buf)).await;
    assert!(
        early_read.is_err(),
        "connection B should still be waiting for a permit while A holds the only slot"
    );

    // Once A's header-read timeout closes it, its permit frees up and B proceeds.
    let n = tokio::time::timeout(Duration::from_millis(500), conn_b.read(&mut buf))
        .await
        .expect("connection B should be served once A's slot frees up")
        .unwrap();
    let response = String::from_utf8_lossy(&buf[..n]);
    assert!(
        response.contains("HTTP/1.1 200"),
        "connection B should succeed after A's slot is released, got: {}",
        response
    );
}

#[tokio::test]
async fn server_shutdown_drains_in_flight_and_stops_accepting() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"content").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // Complete a normal request first, so shutdown() below has nothing genuinely
    // in-flight to race against — the intent here is to verify shutdown() itself
    // completes (rather than hanging) and actually stops the listener, not to
    // reproduce the inherent (and, for a real SIGINT/SIGTERM, vanishingly rare)
    // race between "shutdown fires" and "a brand-new connection is still sitting
    // unaccepted," which `select!`'s fairness makes nondeterministic by design —
    // the same design mini-serve's identical accept/shutdown race has.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);
    assert!(
        response.contains("HTTP/1.1 200") && response.contains("content"),
        "request before shutdown should succeed normally, got: {}",
        response
    );

    // shutdown() must actually complete (not hang waiting on something that never
    // resolves) and must stop the accept loop.
    tokio::time::timeout(Duration::from_secs(2), handle.shutdown())
        .await
        .expect("shutdown() should complete promptly, not hang");

    let reconnect = TcpStream::connect(&addr).await;
    assert!(
        reconnect.is_err(),
        "server should stop accepting new connections after shutdown"
    );
}

#[tokio::test]
async fn server_honors_if_none_match_returns_304() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"file content").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // First request to get the ETag
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "first request should return 200, got: {}",
        response
    );
    assert!(
        response.to_lowercase().contains("etag:"),
        "should have ETag header, got: {}",
        response
    );

    // Extract ETag from response (case-insensitive)
    let etag = response
        .lines()
        .find(|line| line.to_lowercase().starts_with("etag:"))
        .and_then(|line| line.split(": ").nth(1))
        .expect("should have ETag header");

    // Second request with If-None-Match matching the ETag
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    let request = format!(
        "GET /test.txt HTTP/1.1\r\nHost: localhost\r\nIf-None-Match: {}\r\nConnection: close\r\n\r\n",
        etag
    );
    conn.write_all(request.as_bytes()).await.unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 304"),
        "matching If-None-Match should return 304, got: {}",
        response
    );
    assert!(
        !response.contains("file content"),
        "304 should have no body"
    );

    handle.shutdown().await;
}

#[tokio::test]
async fn server_returns_200_on_if_none_match_mismatch() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"file content").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // Request with a non-matching If-None-Match
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nIf-None-Match: \"wrong-etag\"\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "non-matching If-None-Match should return 200, got: {}",
        response
    );
    assert!(response.contains("file content"), "200 should have body");

    handle.shutdown().await;
}

#[tokio::test]
async fn no_cache_header_present_on_200_and_304_responses() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("test.txt"), b"file content").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // First request: plain 200, no conditional headers.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /test.txt HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "expected 200, got: {}",
        response
    );
    assert!(
        response.to_lowercase().contains("cache-control: no-cache"),
        "200 response should carry Cache-Control: no-cache, got: {}",
        response
    );

    let etag = response
        .lines()
        .find(|line| line.to_lowercase().starts_with("etag:"))
        .and_then(|line| line.split(": ").nth(1))
        .expect("should have ETag header")
        .to_string();

    // Second request: matching If-None-Match, expect 304 with the same header.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    let request = format!(
        "GET /test.txt HTTP/1.1\r\nHost: localhost\r\nIf-None-Match: {}\r\nConnection: close\r\n\r\n",
        etag
    );
    conn.write_all(request.as_bytes()).await.unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 304"),
        "expected 304, got: {}",
        response
    );
    assert!(
        response.to_lowercase().contains("cache-control: no-cache"),
        "304 response should carry Cache-Control: no-cache, got: {}",
        response
    );

    handle.shutdown().await;
}

#[tokio::test]
async fn precompressed_sidecar_served_when_accept_encoding_matches() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.js"), b"console.log('plain');").unwrap();
    fs::write(root.path().join("app.js.gz"), b"gzip-sidecar-bytes").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // Request with Accept-Encoding: gzip should get the sidecar's bytes.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /app.js HTTP/1.1\r\nHost: localhost\r\nAccept-Encoding: gzip\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "expected 200, got: {}",
        response
    );
    assert!(
        response.to_lowercase().contains("content-encoding: gzip"),
        "should carry Content-Encoding: gzip, got: {}",
        response
    );
    assert!(
        response.contains("gzip-sidecar-bytes"),
        "should serve the sidecar's bytes, got: {}",
        response
    );
    assert!(
        !response.contains("console.log('plain');"),
        "should not serve the plain file's bytes when a sidecar is chosen, got: {}",
        response
    );

    // Request with no Accept-Encoding should get the plain file unchanged.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /app.js HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);

    assert!(
        response.contains("HTTP/1.1 200"),
        "expected 200, got: {}",
        response
    );
    assert!(
        !response.to_lowercase().contains("content-encoding:"),
        "plain request should carry no Content-Encoding, got: {}",
        response
    );
    assert!(
        response.contains("console.log('plain');"),
        "should serve the plain file's bytes unchanged, got: {}",
        response
    );

    handle.shutdown().await;
}

#[tokio::test]
async fn etag_reflects_the_served_sidecar_variant() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.js"), b"console.log('plain');").unwrap();
    fs::write(root.path().join("app.js.gz"), b"gzip-sidecar-bytes").unwrap();

    let server = Server::new(root.path()).unwrap();
    let (port, handle) = server.run_ephemeral().await.unwrap();

    tokio::time::sleep(Duration::from_millis(10)).await;
    let addr = format!("127.0.0.1:{}", port);

    // First request for the gzip variant: capture its ETag.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /app.js HTTP/1.1\r\nHost: localhost\r\nAccept-Encoding: gzip\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);
    let gzip_etag = response
        .lines()
        .find(|line| line.to_lowercase().starts_with("etag:"))
        .and_then(|line| line.split(": ").nth(1))
        .expect("should have ETag header")
        .to_string();

    // Sending that ETag back as If-None-Match with the same Accept-Encoding should 304.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    let request = format!(
        "GET /app.js HTTP/1.1\r\nHost: localhost\r\nAccept-Encoding: gzip\r\nIf-None-Match: {}\r\nConnection: close\r\n\r\n",
        gzip_etag
    );
    conn.write_all(request.as_bytes()).await.unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);
    assert!(
        response.contains("HTTP/1.1 304"),
        "matching gzip-variant ETag should 304, got: {}",
        response
    );

    // The plain (no Accept-Encoding) variant must carry a different ETag.
    let mut conn = TcpStream::connect(&addr).await.unwrap();
    conn.write_all(b"GET /app.js HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response_data = Vec::new();
    conn.read_to_end(&mut response_data).await.unwrap();
    let response = String::from_utf8_lossy(&response_data);
    let plain_etag = response
        .lines()
        .find(|line| line.to_lowercase().starts_with("etag:"))
        .and_then(|line| line.split(": ").nth(1))
        .expect("should have ETag header")
        .to_string();

    assert_ne!(
        gzip_etag.trim(),
        plain_etag.trim(),
        "gzip and plain variants should have different ETags"
    );

    handle.shutdown().await;
}

/// `without_precompressed()` stops the `.br`/`.gz` lookup, and the plain file is served in
/// its place rather than the request failing.
///
/// Asserted in both directions against the same root: with the default the sidecar is
/// served, with the flag it is not. A one-directional test would pass against a server that
/// had stopped serving sidecars for an unrelated reason.
#[tokio::test]
async fn without_precompressed_serves_the_plain_file_instead_of_the_sidecar() {
    async fn fetch(server: Server) -> String {
        let (port, handle) = server.run_ephemeral().await.unwrap();
        tokio::time::sleep(Duration::from_millis(10)).await;
        let mut conn = TcpStream::connect(format!("127.0.0.1:{port}")).await.unwrap();
        conn.write_all(
            b"GET /app.js HTTP/1.1\r\nHost: localhost\r\n\
              Accept-Encoding: br, gzip\r\nConnection: close\r\n\r\n",
        )
        .await
        .unwrap();
        let mut data = Vec::new();
        conn.read_to_end(&mut data).await.unwrap();
        handle.shutdown().await;
        String::from_utf8_lossy(&data).into_owned()
    }

    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.js"), b"the original bytes").unwrap();
    fs::write(root.path().join("app.js.br"), b"BROTLI").unwrap();

    let with = fetch(Server::new(root.path()).unwrap()).await;
    assert!(
        with.to_lowercase().contains("content-encoding: br") && with.contains("BROTLI"),
        "the default should still serve the sidecar: {with}"
    );

    let without = fetch(Server::new(root.path()).unwrap().without_precompressed()).await;
    assert!(
        !without.to_lowercase().contains("content-encoding:"),
        "a sidecar was served despite without_precompressed(): {without}"
    );
    assert!(
        without.contains("the original bytes"),
        "the plain file was not served: {without}"
    );
}

/// `with_content_cache` reads the root at construction and logs what it holds — and serving is
/// unchanged, because nothing reads the cache yet.
///
/// The log line is the observable part of this commit: population is otherwise invisible by
/// design, and asserting it through the builder rather than through `cache::populate` proves
/// the two are actually wired together.
#[tokio::test]
async fn with_content_cache_populates_and_reports_what_it_holds() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.css"), b"body{}").unwrap();
    fs::write(root.path().join("app.css.br"), b"brotli").unwrap();

    let log = std::sync::Arc::new(std::sync::Mutex::new(Vec::<u8>::new()));
    struct Shared(std::sync::Arc<std::sync::Mutex<Vec<u8>>>);
    impl std::io::Write for Shared {
        fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
            self.0.lock().unwrap().extend_from_slice(buf);
            Ok(buf.len())
        }
        fn flush(&mut self) -> std::io::Result<()> {
            Ok(())
        }
    }

    let server = Server::new(root.path())
        .unwrap()
        .with_request_logging_to(Box::new(Shared(std::sync::Arc::clone(&log))))
        .with_content_cache(1 << 20)
        .expect("no live-reload configured, so no conflict");

    let recorded = String::from_utf8(log.lock().unwrap().clone()).unwrap();
    assert!(
        recorded.contains("content cache: 2 files"),
        "both app.css and its .br sibling are cacheable files: {recorded:?}"
    );
    assert!(
        recorded.contains("1 with precompressed siblings"),
        "app.css has a .br sibling and should be reported: {recorded:?}"
    );

    // Serving is untouched: this commit populates and reads nothing.
    let (port, handle) = server.run_ephemeral().await.unwrap();
    tokio::time::sleep(Duration::from_millis(10)).await;
    let mut conn = TcpStream::connect(format!("127.0.0.1:{port}")).await.unwrap();
    conn.write_all(b"GET /app.css HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response = Vec::new();
    conn.read_to_end(&mut response).await.unwrap();
    handle.shutdown().await;
    let response = String::from_utf8_lossy(&response);

    assert!(response.starts_with("HTTP/1.1 200"), "got: {response}");
    assert!(response.contains("body{}"), "the file should still serve: {response}");
}

/// A cache and live-reload contradict each other, and the contradiction is refused at every
/// entry point — not documented and hoped for.
///
/// Live-reload watches the root because files change; the cache is never invalidated because
/// they do not. Serving stale bytes while a watcher announces changes is the worst available
/// outcome, so all three ways to start a server refuse it.
#[tokio::test]
async fn a_cache_and_live_reload_cannot_both_be_enabled() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.css"), b"body{}").unwrap();

    // Cache added second: refused at the call that created the contradiction.
    let refused = Server::new(root.path())
        .unwrap()
        .with_live_reload()
        .with_content_cache(1 << 20);
    assert!(
        refused.is_err(),
        "with_content_cache must refuse when live-reload is already enabled"
    );

    // Live-reload added second: `with_live_reload` returns `Self` and cannot report, so the
    // refusal lands at start-up instead — before the listener accepts anything.
    let started = Server::new(root.path())
        .unwrap()
        .with_content_cache(1 << 20)
        .expect("cache alone is fine")
        .with_live_reload()
        .run_ephemeral()
        .await;
    assert!(
        started.is_err(),
        "run_ephemeral must refuse to start a server holding both"
    );

    // Either alone is fine, or the test above would pass against a server that refused
    // everything.
    assert!(Server::new(root.path()).unwrap().with_live_reload().run_ephemeral().await.is_ok());
    assert!(
        Server::new(root.path())
            .unwrap()
            .with_content_cache(1 << 20)
            .expect("cache alone is fine")
            .run_ephemeral()
            .await
            .is_ok()
    );
}

/// The composed path never calls `run_on`, so it needs its own refusal. It cannot return an
/// error — `into_fallback` yields a `Handler` — so every request fails loudly instead.
#[tokio::test]
async fn a_composed_server_holding_both_fails_every_request() {
    let root = TempDir::new().unwrap();
    fs::write(root.path().join("app.css"), b"body{}").unwrap();

    let files = Server::new(root.path())
        .unwrap()
        .with_content_cache(1 << 20)
        .expect("cache alone is fine")
        .with_live_reload();

    let port = mini_serve::RouteBuilder::stateless()
        .with_fallback(files.into_fallback())
        .seal()
        .bind_ephemeral()
        .await
        .unwrap();

    let mut conn = TcpStream::connect(format!("127.0.0.1:{port}")).await.unwrap();
    conn.write_all(b"GET /app.css HTTP/1.1\r\nHost: localhost\r\nConnection: close\r\n\r\n")
        .await
        .unwrap();
    let mut response = Vec::new();
    conn.read_to_end(&mut response).await.unwrap();
    let response = String::from_utf8_lossy(&response);

    assert!(
        response.starts_with("HTTP/1.1 500"),
        "a misconfigured composed server must fail loudly rather than serve stale bytes: \
         {response}"
    );
    assert!(
        !response.contains("body{}"),
        "the file was served despite the contradiction: {response}"
    );
}