Merge rust-bitcoin/rust-bitcoin#633: Document cargo features

95fb4e01f9 Document cargo features (Martin Habovstiak)

Pull request description:

  This documents cargo features in two ways: explictly in text and in code
  using `#[doc(cfg(...))]` attribute where possible. Notably, this is
  impossible for `serde` derives. The attribute is contitional and only
  activated for docs.rs or explicit local builds.

  This change also adds `package.metadata.docs.rs` field to `Cargo.toml`
  which instructs docs.rs to build with relevant features and with
  `docsrs` config activated enabling `#[doc(cfg(...))] attributes.

  I also took the opportunity to fix a few missing spaces in nearby code.

  Notes for reviewers:

  * To build and look at result locally run: `RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --features std,secp-recovery,base64,rand,use-serde,bitcoinconsensus --open` (don't confuse `RUSTDOCFLAGS` with `RUSTFLAGS` - took me a while to figure that out 😞)
  * You should see needed features being called out - e.g. in `Script::verify`
  * More information and some screenshots: https://github.com/rust-lang/cargo/issues/8103#issuecomment-653154049
  * For an example why this matters see: https://github.com/Kixunil/loptos/issues/1 😉
  * Serde issue: https://github.com/serde-rs/serde/issues/2063

ACKs for top commit:
  dr-orlovsky:
    ACK 95fb4e01f9
  apoelstra:
    ACK 95fb4e01f9

Tree-SHA512: 4d6428bfa05cbeb2d8737f0239aa1836b5f36f4b040e1ac5e0862663c4ea783711d122182dd8313913fd593ab224915bd8def5e268b272215bee2c9856a27674

Cargo.toml

@@ -10,7 +10,7 @@ description = "General purpose library for using and interoperating with Bitcoin
 keywords = [ "crypto", "bitcoin" ]
 readme = "README.md"
 
-
+# Please don't forget to add relevant features to docs.rs below
 [features]
 default = [ "std", "secp-recovery" ]
 base64 = [ "base64-compat" ]
@@ -28,6 +28,10 @@ secp-recovery = ["secp256k1/recovery"]
 std = ["secp256k1/std", "bitcoin_hashes/std", "bech32/std"]
 no-std = ["hashbrown", "core2/alloc", "bitcoin_hashes/alloc"]
 
+[package.metadata.docs.rs]
+features = [ "std", "secp-recovery", "base64", "rand", "use-serde", "bitcoinconsensus" ]
+rustc-args = ["--cfg", "docsrs"]
+
 [dependencies]
 bech32 = { version = "0.8.1", default-features = false }
 bitcoin_hashes = { version = "0.10.0", default-features = false }

src/blockdata/opcodes.rs

@@ -715,6 +715,7 @@ impl From<u8> for All {
 display_from_debug!(All);
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl serde::Serialize for All {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -753,6 +754,7 @@ pub enum Class {
 display_from_debug!(Class);
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl serde::Serialize for Class {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where

src/blockdata/script.rs

@@ -119,13 +119,16 @@ pub enum Error {
     EarlyEndOfScript,
     /// Tried to read an array off the stack as a number when it was more than 4 bytes
     NumericOverflow,
-    #[cfg(feature="bitcoinconsensus")]
+    #[cfg(feature = "bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Error validating the script with bitcoinconsensus library
     BitcoinConsensus(bitcoinconsensus::Error),
-    #[cfg(feature="bitcoinconsensus")]
+    #[cfg(feature = "bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Can not find the spent output
     UnknownSpentOutput(OutPoint),
-    #[cfg(feature="bitcoinconsensus")]
+    #[cfg(feature = "bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Can not serialize the spending transaction
     SerializationError
 }
@@ -148,6 +151,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {}
 
 #[cfg(feature="bitcoinconsensus")]
@@ -452,12 +456,14 @@ impl Script {
     }
 
     #[cfg(feature="bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Shorthand for [Self::verify_with_flags] with flag [bitcoinconsensus::VERIFY_ALL]
     pub fn verify (&self, index: usize, amount: ::Amount, spending: &[u8]) -> Result<(), Error> {
         self.verify_with_flags(index, amount, spending, ::bitcoinconsensus::VERIFY_ALL)
     }
 
     #[cfg(feature="bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Verify spend of an input script
     /// # Parameters
     ///  * `index` - the input index in spending which is spending this transaction
@@ -817,6 +823,7 @@ impl From<Vec<u8>> for Builder {
 impl_index_newtype!(Builder, u8);
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<'de> serde::Deserialize<'de> for Script {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where D: serde::Deserializer<'de>,
@@ -876,6 +883,7 @@ impl<'de> serde::Deserialize<'de> for Script {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl serde::Serialize for Script {
     /// User-facing serialization for `Script`.
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

src/blockdata/transaction.rs

@@ -133,6 +133,7 @@ impl fmt::Display for ParseOutPointError {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl  error::Error for ParseOutPointError {
     fn cause(&self) -> Option<&dyn  error::Error> {
         match *self {
@@ -501,6 +502,7 @@ impl Transaction {
     }
 
     #[cfg(feature="bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Shorthand for [Self::verify_with_flags] with flag [bitcoinconsensus::VERIFY_ALL]
     pub fn verify<S>(&self, spent: S) -> Result<(), script::Error>
         where S: FnMut(&OutPoint) -> Option<TxOut> {
@@ -508,6 +510,7 @@ impl Transaction {
     }
 
     #[cfg(feature="bitcoinconsensus")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "bitcoinconsensus")))]
     /// Verify that this transaction is able to spend its inputs
     /// The lambda spent should not return the same TxOut twice!
     pub fn verify_with_flags<S, F>(&self, mut spent: S, flags: F) -> Result<(), script::Error>
@@ -667,6 +670,7 @@ impl fmt::Display for NonStandardSigHashType {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl error::Error for NonStandardSigHashType {}
 
 /// Hashtype of an input's signature, encoded in the last byte of the signature

src/consensus/encode.rs

@@ -106,6 +106,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {
     fn cause(&self) -> Option<&dyn  error::Error> {
         match *self {

src/internal_macros.rs

@@ -167,6 +167,7 @@ macro_rules! hex_hash (($h:ident, $s:expr) => ($h::from_slice(&<$crate::prelude:
 macro_rules! serde_string_impl {
     ($name:ident, $expecting:expr) => {
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Deserialize<'de> for $name {
             fn deserialize<D>(deserializer: D) -> Result<$name, D::Error>
             where
@@ -210,6 +211,7 @@ macro_rules! serde_string_impl {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Serialize for $name {
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where
@@ -226,6 +228,7 @@ macro_rules! serde_string_impl {
 macro_rules! serde_struct_human_string_impl {
     ($name:ident, $expecting:expr, $($fe:ident),*) => (
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Deserialize<'de> for $name {
             fn deserialize<D>(deserializer: D) -> Result<$name, D::Error>
             where
@@ -380,6 +383,7 @@ macro_rules! serde_struct_human_string_impl {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Serialize for $name {
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where
@@ -461,7 +465,8 @@ macro_rules! impl_bytes_newtype {
             }
         }
 
-        #[cfg(feature="serde")]
+        #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl $crate::serde::Serialize for $t {
             fn serialize<S: $crate::serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
                 if s.is_human_readable() {
@@ -472,7 +477,8 @@ macro_rules! impl_bytes_newtype {
             }
         }
 
-        #[cfg(feature="serde")]
+        #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Deserialize<'de> for $t {
             fn deserialize<D: $crate::serde::Deserializer<'de>>(d: D) -> Result<$t, D::Error> {
                 if d.is_human_readable() {
@@ -576,6 +582,7 @@ macro_rules! user_enum {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Deserialize<'de> for $name {
             #[inline]
             fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
@@ -625,6 +632,7 @@ macro_rules! user_enum {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl $crate::serde::Serialize for $name {
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where

src/lib.rs

@@ -22,12 +22,27 @@
 //! safety, including ownership and lifetime, for financial and/or cryptographic
 //! software.
 //!
+//! ## Available feature flags
+//!
+//! * `std` - the usual dependency on `std` (default).
+//! * `secp-recovery` - enables calculating public key from a signature and message.
+//! * `base64` - (dependency), enables encoding of PSBTs and message signatures.
+//! * `unstable` - enables unstable features for testing.
+//! * `rand` - (dependency) makes it more convenient to generate random values.
+//! * `use-serde` - (dependency) implements `serde`-based serialization and
+//!                 deserialization
+//! * `secp-lowmemory` - optimizations for low-memory devices
+//! * `no-std` - enables additional features required for this crate to be usable
+//!              without std. Does **not** disable `std`. Depends on `hashbrown`
+//!              and `core2`.
 
 #![cfg_attr(all(not(feature = "std"), not(test)), no_std)]
 
 // Experimental features we need
 #![cfg_attr(all(test, feature = "unstable"), feature(test))]
 
+#![cfg_attr(docsrs, feature(doc_cfg))]
+
 // Coding conventions
 #![forbid(unsafe_code)]
 #![deny(non_upper_case_globals)]
@@ -60,7 +75,9 @@ pub extern crate bech32;
 #[cfg(feature = "no-std")]
 extern crate hashbrown;
 
-#[cfg(feature = "base64")] pub extern crate base64;
+#[cfg(feature = "base64")]
+#[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
+pub extern crate base64;
 
 #[cfg(feature="bitcoinconsensus")] extern crate bitcoinconsensus;
 #[cfg(feature = "serde")] #[macro_use] extern crate serde;

src/network/mod.rs

@@ -24,14 +24,30 @@ use core::fmt;
 
 pub mod constants;
 
-#[cfg(feature = "std")] pub mod address;
+#[cfg(feature = "std")]
-#[cfg(feature = "std")] pub use self::address::Address;
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
-#[cfg(feature = "std")] pub mod message;
+pub mod address;
-#[cfg(feature = "std")] pub mod message_blockdata;
+#[cfg(feature = "std")]
-#[cfg(feature = "std")] pub mod message_bloom;
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
-#[cfg(feature = "std")] pub mod message_network;
+pub use self::address::Address;
-#[cfg(feature = "std")] pub mod message_filter;
+#[cfg(feature = "std")]
-#[cfg(feature = "std")] pub mod stream_reader;
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod message;
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod message_blockdata;
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod message_bloom;
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod message_network;
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod message_filter;
+#[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
+pub mod stream_reader;
 
 /// Network error
 #[derive(Debug)]
@@ -62,6 +78,7 @@ impl From<io::Error> for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl error::Error for Error {
     fn cause(&self) -> Option<&dyn error::Error> {
         match *self {

src/util/address.rs

@@ -96,6 +96,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {
     fn cause(&self) -> Option<&dyn  error::Error> {
         match *self {

src/util/amount.rs

@@ -114,6 +114,7 @@ impl fmt::Display for ParseAmountError {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for ParseAmountError {}
 
 fn is_too_precise(s: &str, precision: usize) -> bool {
@@ -902,6 +903,7 @@ mod private {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 pub mod serde {
     // methods are implementation of a standardized serde-specific signature
     #![allow(missing_docs)]
@@ -1008,7 +1010,7 @@ pub mod serde {
     }
 
     pub mod as_sat {
-        //! Serialize and deserialize [Amount] as real numbers denominated in satoshi.
+        //! Serialize and deserialize [`Amount`](crate::Amount) as real numbers denominated in satoshi.
         //! Use with `#[serde(with = "amount::serde::as_sat")]`.
 
         use serde::{Deserializer, Serializer};
@@ -1023,7 +1025,7 @@ pub mod serde {
         }
 
         pub mod opt {
-            //! Serialize and deserialize [Optoin<Amount>] as real numbers denominated in satoshi.
+            //! Serialize and deserialize [`Option<Amount>`](crate::Amount) as real numbers denominated in satoshi.
             //! Use with `#[serde(default, with = "amount::serde::as_sat::opt")]`.
 
             use serde::{Deserializer, Serializer, de};
@@ -1071,7 +1073,7 @@ pub mod serde {
     }
 
     pub mod as_btc {
-        //! Serialize and deserialize [Amount] as JSON numbers denominated in BTC.
+        //! Serialize and deserialize [`Amount`](crate::Amount) as JSON numbers denominated in BTC.
         //! Use with `#[serde(with = "amount::serde::as_btc")]`.
 
         use serde::{Deserializer, Serializer};

src/util/base58.rs

@@ -59,6 +59,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {}
 
 /// Vector-like object that holds the first 100 elements on the stack. If more space is needed it

src/util/bip158.rs

@@ -75,6 +75,7 @@ pub enum Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {}
 
 impl Display for Error {

src/util/bip32.rs

@@ -194,6 +194,7 @@ impl FromStr for ChildNumber {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<'de> serde::Deserialize<'de> for ChildNumber {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
@@ -204,6 +205,7 @@ impl<'de> serde::Deserialize<'de> for ChildNumber {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl serde::Serialize for ChildNumber {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where
@@ -460,6 +462,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl error::Error for Error {
     fn cause(&self) -> Option<&dyn error::Error> {
        if let Error::Secp256k1(ref e) = *self {

src/util/contracthash.rs

@@ -75,6 +75,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {
     fn cause(&self) -> Option<&dyn error::Error> {
         match *self {

src/util/ecdsa.rs

@@ -297,6 +297,7 @@ impl ops::Index<ops::RangeFull> for PrivateKey {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl ::serde::Serialize for PrivateKey {
     fn serialize<S: ::serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
         s.collect_str(self)
@@ -304,6 +305,7 @@ impl ::serde::Serialize for PrivateKey {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<'de> ::serde::Deserialize<'de> for PrivateKey {
     fn deserialize<D: ::serde::Deserializer<'de>>(d: D) -> Result<PrivateKey, D::Error> {
         struct WifVisitor;
@@ -339,6 +341,7 @@ impl<'de> ::serde::Deserialize<'de> for PrivateKey {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl ::serde::Serialize for PublicKey {
     fn serialize<S: ::serde::Serializer>(&self, s: S) -> Result<S::Ok, S::Error> {
         if s.is_human_readable() {
@@ -354,6 +357,7 @@ impl ::serde::Serialize for PublicKey {
 }
 
 #[cfg(feature = "serde")]
+#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<'de> ::serde::Deserialize<'de> for PublicKey {
     fn deserialize<D: ::serde::Deserializer<'de>>(d: D) -> Result<PublicKey, D::Error> {
         if d.is_human_readable() {

src/util/key.rs

@@ -45,6 +45,7 @@ impl fmt::Display for Error {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for Error {
     fn cause(&self) -> Option<&dyn error::Error> {
         match *self {

src/util/merkleblock.rs

@@ -438,6 +438,7 @@ impl MerkleBlock {
 
     /// Create a MerkleBlock from a block, that contains proofs for specific txids.
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     #[deprecated(since="0.26.2", note="use from_block_with_predicate")]
     pub fn from_block(block: &Block, match_txids: &::std::collections::HashSet<Txid>) -> Self {
         Self::from_block_with_predicate(block, |t| match_txids.contains(t))
@@ -466,6 +467,7 @@ impl MerkleBlock {
 
     /// Create a MerkleBlock from the block's header and txids, that should contain proofs for match_txids.
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     #[deprecated(since="0.26.2", note="use from_header_txids_with_predicate")]
     pub fn from_header_txids(
         header: &BlockHeader,

src/util/misc.rs

@@ -24,6 +24,7 @@ use blockdata::opcodes;
 use consensus::{encode, Encodable};
 
 #[cfg(feature = "secp-recovery")]
+#[cfg_attr(docsrs, doc(cfg(feature = "secp-recovery")))]
 pub use self::message_signing::{MessageSignature, MessageSignatureError};
 
 /// The prefix for signed messages using Bitcoin's message signing protocol.
@@ -43,6 +44,7 @@ mod message_signing {
     use util::address::{Address, AddressType};
 
     /// An error used for dealing with Bitcoin Signed Messages.
+    #[cfg_attr(docsrs, doc(cfg(feature = "secp-recovery")))]
     #[derive(Debug, PartialEq, Eq)]
     pub enum MessageSignatureError {
         /// Signature is expected to be 65 bytes.
@@ -64,6 +66,7 @@ mod message_signing {
     }
 
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     impl error::Error for MessageSignatureError {
         fn cause(&self) -> Option<&dyn error::Error> {
             match *self {
@@ -86,6 +89,7 @@ mod message_signing {
     /// `fmt::Display` and `str::FromStr` implementations, the `base64` feature
     /// must be enabled.
     #[derive(Copy, Clone, PartialEq, Eq, Debug)]
+    #[cfg_attr(docsrs, doc(cfg(feature = "secp-recovery")))]
     pub struct MessageSignature {
         /// The inner recoverable signature.
         pub signature: RecoverableSignature,
@@ -169,6 +173,7 @@ mod message_signing {
         }
 
         #[cfg(feature = "base64")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
         /// Convert a signature from base64 encoding.
         pub fn from_base64(s: &str) -> Result<MessageSignature, MessageSignatureError> {
             let bytes = ::base64::decode(s).map_err(|_| MessageSignatureError::InvalidBase64)?;
@@ -176,6 +181,7 @@ mod message_signing {
         }
 
         #[cfg(feature = "base64")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
         /// Convert to base64 encoding.
         pub fn to_base64(&self) -> String {
             ::base64::encode(&self.serialize()[..])
@@ -183,6 +189,7 @@ mod message_signing {
     }
 
     #[cfg(feature = "base64")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
     impl fmt::Display for MessageSignature {
         fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
             let bytes = self.serialize();
@@ -193,6 +200,7 @@ mod message_signing {
     }
 
     #[cfg(feature = "base64")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
     impl ::core::str::FromStr for MessageSignature {
         type Err = MessageSignatureError;
         fn from_str(s: &str) -> Result<MessageSignature, MessageSignatureError> {

src/util/psbt/mod.rs

@@ -104,6 +104,7 @@ mod display_from_str {
 
     /// Error happening during PSBT decoding from Base64 string
     #[derive(Debug)]
+    #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
     pub enum PsbtParseError {
         /// Error in internal PSBT data structure
         PsbtEncoding(Error),
@@ -121,14 +122,17 @@ mod display_from_str {
     }
 
     #[cfg(feature = "std")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
     impl ::std::error::Error for PsbtParseError { }
 
+    #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
     impl Display for PartiallySignedTransaction {
         fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
             write!(f, "{}", Base64Display::with_config(&encode::serialize(self), ::base64::STANDARD))
         }
     }
 
+    #[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
     impl FromStr for PartiallySignedTransaction {
         type Err = PsbtParseError;
 
@@ -139,6 +143,7 @@ mod display_from_str {
     }
 }
 #[cfg(feature = "base64")]
+#[cfg_attr(docsrs, doc(cfg(feature = "base64")))]
 pub use self::display_from_str::PsbtParseError;
 
 impl Encodable for PartiallySignedTransaction {

src/util/uint.rs

@@ -430,6 +430,7 @@ macro_rules! construct_uint {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl $crate::serde::Serialize for $name {
             fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
             where
@@ -446,6 +447,7 @@ macro_rules! construct_uint {
         }
 
         #[cfg(feature = "serde")]
+        #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
         impl<'de> $crate::serde::Deserialize<'de> for $name {
             fn deserialize<D: $crate::serde::Deserializer<'de>>(
                 deserializer: D,
@@ -510,6 +512,7 @@ impl ::core::fmt::Display for ParseLengthError {
 }
 
 #[cfg(feature = "std")]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl ::std::error::Error for ParseLengthError {}
 
 impl Uint256 {