Adds CI matrix for crate features

.github/workflows/rust.yml

@@ -17,6 +17,8 @@ jobs:
         # meantime, the build only tests Windows Server 2019.
         # See https://github.com/amazon-ion/ion-rust/issues/353
         os: [ubuntu-latest, windows-2019, macos-latest]
+        # build and test for different and interesting crate features
+        features: ['default', 'all', 'ion-hash', 'experimental', 'ion-hash,experimental']
     permissions:
       checks: write
 
@@ -39,22 +41,27 @@ jobs:
           toolchain: stable
           components: rustfmt, clippy
           override: true
-      - name: Cargo Build
-        uses: actions-rs/cargo@v1
-        with:
-          command: build
-          args: --verbose --workspace
       - name: Cargo Test (default/no features)
+        if: matrix.features == 'default'
         uses: actions-rs/cargo@v1
         with:
           command: test
           args: --verbose --workspace
       - name: Cargo Test (all features)
+        if: matrix.features == 'all'
         uses: actions-rs/cargo@v1
         with:
           command: test
           args: --verbose --workspace --all-features
+      - name: Cargo Test (specific feature)
+        if: matrix.features != 'default' && matrix.features != 'all'
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: --verbose --workspace --features "${{ matrix.features }}"
       - name: Rustfmt Check
+        # We really only need to run this once--ubuntu/all features mode is as good as any
+        if: matrix.os == 'ubuntu-latest' && matrix.features == 'all'
         uses: actions-rs/cargo@v1
         with:
           command: fmt
@@ -68,16 +75,18 @@ jobs:
         # The clippy check depends on setup steps defined above, but we don't want it to run
         # for every OS because it posts its comments to the PR. These `if` checks limit clippy to
         # only running on the Linux test. (The choice of OS was arbitrary.)
-        if: matrix.os == 'ubuntu-latest'
+        if: matrix.os == 'ubuntu-latest' && matrix.features == 'all'
         run: rustup component add clippy
-      - name: Run Clippy
-        if: matrix.os == 'ubuntu-latest'
+      - name: Run Clippy 
+        if: matrix.os == 'ubuntu-latest' && matrix.features == 'all'
         uses: actions-rs/clippy-check@v1
         with:
           # Adding comments to the PR requires the GITHUB_TOKEN secret.
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features --tests
       - name: Rustdoc on Everything
+        # We really only need to run this once--ubuntu/all features mode is as good as any
+        if: matrix.os == 'ubuntu-latest' && matrix.features == 'all'
         uses: actions-rs/cargo@v1
         with:
           command: doc

src/ion_data/mod.rs

@@ -18,7 +18,6 @@ pub(crate) use ion_ord::IonOrd;
 ///
 /// Equivalence with respect to Ion values means that if two Ion values, `X` and `Y`, are equivalent,
 /// they represent the same data and can be substituted for the other without loss of information.
-/// (See [`IonEq`] for more information.)
 ///
 /// Some types, such as [`Element`](crate::Element) and [`Value`](crate::element::Value) cannot be
 /// used as the key of a map because they adhere to Rust value semantics—these types cannot implement
@@ -31,11 +30,11 @@ pub(crate) use ion_ord::IonOrd;
 /// For other use cases, such as using Ion data as the key of a map or passing Ion data to an
 /// algorithm that depends on [`Eq`], you can lift values using [`IonData::from()`].
 ///
-/// Anything that implements [`IonEq`] can be converted into [`IonData`]. [`IonData`] itself does not
-/// implement [`IonEq`] so that it is impossible to create, for example, `IonData<IonData<Element>>`.
+/// Generally, anything that is treated as Ion data (e.g., [`Element`](crate::Element) and
+/// [`Value`](crate::element::Value)), can be converted to [`IonData`].
 ///
 /// [`Hash`] and [`Ord`] are not guaranteed to be implemented for all [`IonData`], but when they are,
-/// they are required to be consistent with [`IonEq`] (and [`Eq`]).
+/// they are required to be consistent with Ion structural equality (and [`Eq`]).
 ///
 /// __WARNING__—The Ion specification does _not_ define a total ordering over all Ion values. Do
 /// not depend on getting any particular result from [Ord]. Use it only as an opaque total ordering

src/ion_hash/mod.rs

@@ -8,15 +8,19 @@
 //! use ion_rs::result::IonResult;
 //! use ion_rs::ion_hash;
 //!
+//! # // XXX this doc test requires an optional feature--so this makes sure we can still run tests
+//! # #[cfg(feature = "sha2")]
 //! # fn main() -> IonResult<()> {
 //!   let elem = Element::read_one(b"\"hello world\"")?;
 //!   let digest = ion_hash::sha256(&elem);
 //!   println!("{:?}", digest);
 //! # Ok(())
 //! # }
+//! # #[cfg(not(feature = "sha2"))]
+//! # fn main() {}
 //! ```
 
 use digest::{self, FixedOutput, Output, Reset, Update};
 
 use crate::element::Element;
 use crate::IonResult;

src/lib.rs

@@ -1,5 +1,6 @@
 #![allow(dead_code)]
 #![deny(rustdoc::broken_intra_doc_links)]
+#![deny(rustdoc::private_intra_doc_links)]
 #![deny(rustdoc::bare_urls)]
 //! # Reading and writing `Element`s
 //!