chore: Use derive_more to reduce boilerplate (#3290)

* chore: Use `derive_more` to reduce boilerplate

Already a dependency in Gecko. Let's us reduce boilerplate quite a bit.

* Fix

* Address comments

* Fix

---------

Signed-off-by: Lars Eggert <lars@eggert.org>

Author: larseggert

Cargo.lock

@@ -12,6 +12,7 @@ description = "Gecko API for NSS"
 repository = "https://github.com/mozilla/nss-rs"
 
 [dependencies]
+derive_more = { version = "2.0", default-features = false, features = ["display", "debug", "deref", "deref_mut", "from", "into", "add", "as_ref"] }
 enum-map = { version = "2.7", default-features = false }
 once_cell = "1"
 # Sync with https://searchfox.org/mozilla-central/source/Cargo.lock 2024-02-08

Cargo.toml

@@ -5,7 +5,6 @@
 // except according to those terms.
 
 use std::{
-    fmt,
     os::raw::{c_char, c_int, c_uint},
     ptr::null_mut,
 };
@@ -115,6 +114,8 @@ experimental_api!(SSL_AeadDecrypt(
 experimental_api!(SSL_DestroyAead(ctx: *mut SSLAeadContext));
 scoped_ptr!(AeadContext, SSLAeadContext, SSL_DestroyAead);
 
+#[derive(derive_more::Debug)]
+#[debug("[AEAD Context]")]
 pub struct RealAead {
     ctx: AeadContext,
 }
@@ -249,12 +250,6 @@ impl AeadTrait for RealAead {
     }
 }
 
-impl fmt::Debug for RealAead {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "[AEAD Context]")
-    }
-}
-
 /// All the nonces are the same length.  Exploit that.
 pub const NONCE_LEN: usize = 12;
 

src/aead.rs

@@ -4,8 +4,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::fmt;
-
 use crate::{
     aead::AeadTrait,
     constants::{Cipher, Version},
@@ -15,6 +13,8 @@ use crate::{
 
 pub const AEAD_NULL_TAG: &[u8] = &[0x0a; 16];
 
+#[derive(derive_more::Debug)]
+#[debug("[NULL AEAD]")]
 pub struct AeadNull {}
 
 impl AeadNull {
@@ -86,9 +86,3 @@ impl AeadTrait for AeadNull {
         self.decrypt_check(count, aad, data)
     }
 }
-
-impl fmt::Debug for AeadNull {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "[NULL AEAD]")
-    }
-}

src/aead_null.rs

@@ -13,7 +13,7 @@ use std::{
     cell::RefCell,
     convert::{TryFrom as _, TryInto as _},
     ffi::{CStr, CString},
-    fmt::{self, Debug, Display, Formatter, Write as _},
+    fmt::{self, Debug, Formatter, Write as _},
     mem::MaybeUninit,
     ops::{Deref, DerefMut},
     os::raw::{c_uint, c_void},
@@ -438,7 +438,8 @@ impl SecretAgentInfo {
 }
 
 /// `SecretAgent` holds the common parts of client and server.
-#[derive(Debug)]
+#[derive(Debug, derive_more::Display)]
+#[display("Agent {fd:p}")]
 #[expect(clippy::module_name_repetitions, reason = "This is OK.")]
 pub struct SecretAgent {
     fd: *mut prio::PRFileDesc,
@@ -1005,14 +1006,9 @@ impl Drop for SecretAgent {
     }
 }
 
-impl Display for SecretAgent {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "Agent {:p}", self.fd)
-    }
-}
-
-#[derive(PartialOrd, Ord, PartialEq, Eq, Clone)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Clone, derive_more::AsRef)]
 pub struct ResumptionToken {
+    #[as_ref([u8])]
     token: Vec<u8>,
     expiration_time: Instant,
 }
@@ -1026,12 +1022,6 @@ impl Debug for ResumptionToken {
     }
 }
 
-impl AsRef<[u8]> for ResumptionToken {
-    fn as_ref(&self) -> &[u8] {
-        &self.token
-    }
-}
-
 impl ResumptionToken {
     #[must_use]
     pub const fn new(token: Vec<u8>, expiration_time: Instant) -> Self {
@@ -1048,8 +1038,11 @@ impl ResumptionToken {
 }
 
 /// A TLS Client.
-#[derive(Debug)]
+#[derive(Debug, derive_more::Display, derive_more::Deref, derive_more::DerefMut)]
+#[display("Client {:p}", "agent.fd")]
 pub struct Client {
+    #[deref]
+    #[deref_mut]
     agent: SecretAgent,
 
     /// The name of the server we're attempting a connection to.
@@ -1202,25 +1195,6 @@ impl Client {
     }
 }
 
-impl Deref for Client {
-    type Target = SecretAgent;
-    fn deref(&self) -> &SecretAgent {
-        &self.agent
-    }
-}
-
-impl DerefMut for Client {
-    fn deref_mut(&mut self) -> &mut SecretAgent {
-        &mut self.agent
-    }
-}
-
-impl Display for Client {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "Client {:p}", self.agent.fd)
-    }
-}
-
 /// `ZeroRttCheckResult` encapsulates the options for handling a `ClientHello`.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum ZeroRttCheckResult {
@@ -1265,8 +1239,11 @@ impl ZeroRttCheckState {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, derive_more::Display, derive_more::Deref, derive_more::DerefMut)]
+#[display("Server {:p}", "agent.fd")]
 pub struct Server {
+    #[deref]
+    #[deref_mut]
     agent: SecretAgent,
     /// This holds the HRR callback context.
     zero_rtt_check: Option<Pin<Box<ZeroRttCheckState>>>,
@@ -1462,25 +1439,6 @@ impl Server {
     }
 }
 
-impl Deref for Server {
-    type Target = SecretAgent;
-    fn deref(&self) -> &SecretAgent {
-        &self.agent
-    }
-}
-
-impl DerefMut for Server {
-    fn deref_mut(&mut self) -> &mut SecretAgent {
-        &mut self.agent
-    }
-}
-
-impl Display for Server {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "Server {:p}", self.agent.fd)
-    }
-}
-
 /// A generic container for Client or Server.
 #[derive(Debug)]
 pub enum Agent {

src/agent.rs

@@ -12,9 +12,7 @@
 use std::{
     cmp::min,
     convert::{TryFrom as _, TryInto as _},
-    fmt::{self, Display, Formatter},
     mem,
-    ops::Deref,
     os::raw::{c_uint, c_void},
     pin::Pin,
     ptr::{null, null_mut},
@@ -45,7 +43,8 @@ pub fn as_c_void<T: Unpin>(pin: &mut Pin<Box<T>>) -> *mut c_void {
 }
 
 /// A slice of the output.
-#[derive(Default)]
+#[derive(Default, derive_more::Debug)]
+#[debug("Record {:?}:{:?} {}", epoch, ct, hex_with_len(&data[..]))]
 pub struct Record {
     pub epoch: Epoch,
     pub ct: ContentType,
@@ -76,19 +75,7 @@ impl Record {
     }
 }
 
-impl fmt::Debug for Record {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(
-            f,
-            "Record {:?}:{:?} {}",
-            self.epoch,
-            self.ct,
-            hex_with_len(&self.data[..])
-        )
-    }
-}
-
-#[derive(Debug, Default)]
+#[derive(Debug, Default, derive_more::Deref)]
 pub struct RecordList {
     records: Vec<Record>,
 }
@@ -130,13 +117,6 @@ impl RecordList {
     }
 }
 
-impl Deref for RecordList {
-    type Target = Vec<Record>;
-    fn deref(&self) -> &Vec<Record> {
-        &self.records
-    }
-}
-
 pub struct RecordListIter(std::vec::IntoIter<Record>);
 
 impl Iterator for RecordListIter {
@@ -165,7 +145,8 @@ impl Drop for AgentIoInputContext<'_> {
 }
 
 // TODO: Derive Default when MSRV >= 1.88 (Default for raw pointers stabilized in 1.88).
-#[derive(Debug)]
+#[derive(Debug, derive_more::Display)]
+#[display("AgentIoInput {input:p}")]
 struct AgentIoInput {
     // input is data that is read by TLS.
     input: *const u8,
@@ -221,13 +202,8 @@ impl AgentIoInput {
     }
 }
 
-impl Display for AgentIoInput {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "AgentIoInput {:p}", self.input)
-    }
-}
-
-#[derive(Debug, Default)]
+#[derive(Debug, Default, derive_more::Display)]
+#[display("AgentIo")]
 pub struct AgentIo {
     // input collects the input we might provide to TLS.
     input: AgentIoInput,
@@ -259,12 +235,6 @@ impl AgentIo {
     }
 }
 
-impl Display for AgentIo {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "AgentIo")
-    }
-}
-
 unsafe extern "C" fn agent_close(fd: PrFd) -> PrStatus {
     (*fd).secret = null_mut();
     if let Some(dtor) = (*fd).dtor {

src/agentio.rs

@@ -12,7 +12,6 @@
 use std::{
     cell::RefCell,
     convert::TryFrom as _,
-    fmt::{self, Debug, Formatter},
     os::raw::{c_uint, c_void},
     pin::Pin,
     rc::Rc,
@@ -90,7 +89,10 @@ pub trait ExtensionHandler {
 
 type BoxedExtensionHandler = Box<Rc<RefCell<dyn ExtensionHandler>>>;
 
+#[derive(derive_more::Debug)]
+#[debug("ExtensionTracker: {:?}", extension)]
 pub struct ExtensionTracker {
+    #[expect(dead_code, reason = "Used by derived Debug implementation")]
     extension: Extension,
     handler: Pin<Box<BoxedExtensionHandler>>,
 }
@@ -203,9 +205,3 @@ impl ExtensionTracker {
         Ok(tracker)
     }
 }
-
-impl Debug for ExtensionTracker {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        write!(f, "ExtensionTracker: {:?}", self.extension)
-    }
-}