fix: minimal build with no default features (#731)

* fix: add unreachable variant to DecoderImpl for no enabled decoders

Co-authored-by: @renski-dev

* fix: testing and compilation of tests and examples with no default features

* fix: remove feature gates from FLAC duration checks

* ci: check absolutely minimal build to prevent regression

Author: roderickvd

.github/workflows/ci.yml

@@ -3,7 +3,7 @@ name: CI
 on:
   pull_request:
   push:
-    branches: [ main, master ]
+    branches: [main, master]
 
 env:
   RUSTFLAGS: "-C debuginfo=0 -D warnings"
@@ -18,8 +18,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ macos-latest, windows-latest, ubuntu-latest ]
-        toolchain: [ stable, beta, nightly ]
+        os: [macos-latest, windows-latest, ubuntu-latest]
+        toolchain: [stable, beta, nightly]
         include:
           - os: macos-latest
             MACOS: true
@@ -49,6 +49,5 @@ jobs:
       # `cargo test` does not check benchmarks and `cargo test --all-targets` excludes
       # documentation tests. Therefore, we need an additional docs test command here.
       - run: cargo test --doc
-      # Check minimal build. `tests/seek.rs` fails if there are no decoders at all,
-      # adding one to make the tests check pass.
-      - run: cargo check --tests --lib --no-default-features --features mp3
+      # Check minimal build.
+      - run: cargo check --tests --lib --no-default-features

Cargo.toml

@@ -19,7 +19,10 @@ minimp3_fixed = { version = "0.5.4", optional = true }
 symphonia = { version = "0.5.4", optional = true, default-features = false }
 crossbeam-channel = { version = "0.5.15", optional = true }
 
-rand = { version = "0.9.0", features = ["small_rng", "os_rng"], optional = true }
+rand = { version = "0.9.0", features = [
+    "small_rng",
+    "os_rng",
+], optional = true }
 tracing = { version = "0.1.40", optional = true }
 
 atomic_float = { version = "1.1.0", optional = true }
@@ -72,27 +75,91 @@ divan = "0.1.14"
 [[bench]]
 name = "effects"
 harness = false
+required-features = ["wav"]
 
 [[bench]]
 name = "conversions"
 harness = false
+required-features = ["wav"]
 
 [[bench]]
 name = "resampler"
 harness = false
+required-features = ["wav"]
 
 [[bench]]
 name = "pipeline"
 harness = false
+required-features = ["wav"]
+
+[[example]]
+name = "automatic_gain_control"
+required-features = ["playback", "flac"]
+
+[[example]]
+name = "basic"
+required-features = ["playback", "vorbis"]
+
+[[example]]
+name = "callback_on_end"
+required-features = ["playback", "wav"]
+
+[[example]]
+name = "custom_config"
+required-features = ["playback", "wav"]
+
+[[example]]
+name = "error_callback"
+required-features = ["playback"]
+
+[[example]]
+name = "into_file"
+required-features = ["mp3", "wav"]
+
+[[example]]
+name = "low_pass"
+required-features = ["playback", "wav"]
+
+[[example]]
+name = "mix_multiple_sources"
+required-features = ["playback"]
 
 [[example]]
 name = "music_m4a"
-required-features = ["symphonia-isomp4", "symphonia-aac"]
+required-features = ["playback", "symphonia-isomp4", "symphonia-aac"]
+
+[[example]]
+name = "music_mp3"
+required-features = ["playback", "mp3"]
+
+[[example]]
+name = "music_ogg"
+required-features = ["playback", "vorbis"]
+
+[[example]]
+name = "music_wav"
+required-features = ["playback", "wav"]
 
 [[example]]
 name = "noise_generator"
-required-features = ["noise"]
+required-features = ["playback", "noise"]
 
 [[example]]
-name = "into_file"
-required-features = ["wav", "mp3"]
+name = "reverb"
+required-features = ["playback", "vorbis"]
+
+[[example]]
+name = "seek_mp3"
+required-features = ["playback", "mp3"]
+
+[[example]]
+name = "signal_generator"
+required-features = ["playback"]
+
+[[example]]
+name = "spatial"
+required-features = ["playback", "vorbis"]
+
+[[example]]
+name = "stereo"
+required-features = ["playback", "vorbis"]

examples/noise_generator.rs

@@ -2,7 +2,6 @@
 
 use std::error::Error;
 
-#[cfg(feature = "noise")]
 fn main() -> Result<(), Box<dyn Error>> {
     use rodio::source::{pink, white, Source};
     use std::thread;
@@ -29,9 +28,3 @@ fn main() -> Result<(), Box<dyn Error>> {
 
     Ok(())
 }
-
-#[cfg(not(feature = "noise"))]
-fn main() {
-    println!("rodio has not been compiled with noise sources, use `--features noise` to enable this feature.");
-    println!("Exiting...");
-}

src/decoder/mod.rs

@@ -119,8 +119,14 @@ enum DecoderImpl<R: Read + Seek> {
     Mp3(mp3::Mp3Decoder<R>),
     #[cfg(feature = "symphonia")]
     Symphonia(symphonia::SymphoniaDecoder, PhantomData<R>),
+    // This variant is here just to satisfy the compiler when there are no decoders enabled.
+    // It is unreachable and should never be constructed.
+    #[allow(dead_code)]
+    None(Unreachable, PhantomData<R>),
 }
 
+enum Unreachable {}
+
 impl<R: Read + Seek> DecoderImpl<R> {
     #[inline]
     fn next(&mut self) -> Option<Sample> {
@@ -135,6 +141,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.next(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.next(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -151,6 +158,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.size_hint(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.size_hint(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -167,6 +175,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.current_span_len(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.current_span_len(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -183,6 +192,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.channels(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.channels(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -199,6 +209,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.sample_rate(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.sample_rate(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -221,6 +232,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.total_duration(),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.total_duration(),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 
@@ -237,6 +249,7 @@ impl<R: Read + Seek> DecoderImpl<R> {
             DecoderImpl::Mp3(source) => source.try_seek(pos),
             #[cfg(feature = "symphonia")]
             DecoderImpl::Symphonia(source, PhantomData) => source.try_seek(pos),
+            DecoderImpl::None(_, _) => unreachable!(),
         }
     }
 }

src/lib.rs

@@ -12,7 +12,8 @@
 //!
 //! Here is a complete example of how you would play an audio file:
 //!
-//! ```no_run
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```no_run")]
 //! use std::fs::File;
 //! use rodio::{Decoder, OutputStream, source::Source};
 //!
@@ -34,7 +35,8 @@
 //! ```
 //!
 //! [`rodio::play()`](crate::play) helps to simplify the above
-//! ```no_run
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```no_run")]
 //! use std::fs::File;
 //! use std::io::BufReader;
 //! use rodio::{Decoder, OutputStream, source::Source};
@@ -63,7 +65,8 @@
 //! To play a soung Create a [`Sink`] connect it to the output stream,
 //! and [`.append()`](Sink::append) your sound to it.
 //!
-//! ```no_run
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```no_run")]
 //! use std::time::Duration;
 //! use rodio::{OutputStream, Sink};
 //! use rodio::source::{SineWave, Source};
@@ -96,7 +99,8 @@
 //!
 //! Example:
 //!
-//! ```
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```")]
 //! use rodio::Source;
 //! use std::time::Duration;
 //!
@@ -147,7 +151,15 @@
 //! on the number of sinks that can be created (except for the fact that creating too many will slow
 //! down your program).
 
-#![cfg_attr(test, deny(missing_docs))]
+#![cfg_attr(
+    any(test, not(feature = "playback")),
+    deny(missing_docs),
+    allow(dead_code),
+    allow(unused_imports),
+    allow(unused_variables),
+    allow(unreachable_code)
+)]
+
 #[cfg(feature = "playback")]
 pub use cpal::{
     self, traits::DeviceTrait, Device, Devices, DevicesError, InputDevices, OutputDevices,

src/source/speed.rs

@@ -11,7 +11,8 @@
 //! To speed up a source from sink all you need to do is call the   `set_speed(factor: f32)` function
 //! For example, here is how you speed up your sound by using sink or playing raw:
 //!
-//! ```no_run
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```no_run")]
 //!# use std::fs::File;
 //!# use rodio::{Decoder, Sink, OutputStream, source::{Source, SineWave}};
 //!
@@ -28,7 +29,8 @@
 //! std::thread::sleep(std::time::Duration::from_secs(5));
 //! ```
 //! Here is how you would do it using the sink:
-//!```no_run
+#![cfg_attr(not(feature = "playback"), doc = "```ignore")]
+#![cfg_attr(feature = "playback", doc = "```no_run")]
 //! use rodio::source::{Source, SineWave};
 //! let source = SineWave::new(440.0)
 //!    .take_duration(std::time::Duration::from_secs_f32(20.25))

tests/flac_test.rs

@@ -1,6 +1,6 @@
-#[cfg(all(feature = "flac", not(feature = "symphonia-flac")))]
+#[cfg(any(feature = "flac", feature = "symphonia-flac"))]
 use rodio::Source;
-#[cfg(all(feature = "flac", not(feature = "symphonia-flac")))]
+#[cfg(any(feature = "flac", feature = "symphonia-flac"))]
 use std::time::Duration;
 
 #[cfg(any(feature = "flac", feature = "symphonia-flac"))]
@@ -12,16 +12,13 @@ fn test_flac_encodings() {
 
     // File is not just silence
     assert!(decoder.any(|x| x != 0.0));
-    // Symphonia does not expose functionality to get the duration so this check must be disabled
-    #[cfg(all(feature = "flac", not(feature = "symphonia-flac")))]
     assert_eq!(decoder.total_duration(), Some(Duration::from_secs(3))); // duration is calculated correctly
 
     // 24 bit FLAC file exported from Audacity (2 channels, various compression levels)
     for level in &[0, 5, 8] {
         let file = std::fs::File::open(format!("assets/audacity24bit_level{level}.flac")).unwrap();
         let mut decoder = rodio::Decoder::try_from(file).unwrap();
         assert!(!decoder.all(|x| x != 0.0));
-        #[cfg(all(feature = "flac", not(feature = "symphonia-flac")))]
         assert_eq!(decoder.total_duration(), Some(Duration::from_secs(3)));
     }
 }