Removed duplicate calls for caching in CI. Resolves google#340

.github/actions/cache/action.yml

@@ -0,0 +1,33 @@
+name: Cache
+description: 'Caches cargo dependencies'
+runs:
+  using: composite
+  steps:
+    - uses: actions/cache@v3 
+      with: 
+        path: | 
+          ~/.cargo/ 
+        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
+
+    - name: Download dependencies
+      run: |
+          # Ensure all dependencies are downloaded - both for our crates and for
+          # tools we use in CI. We don't care about these tools succeeding for
+          # two reasons: First, this entire job is best-effort since it's just a
+          # performance optimization. Second, there may be failures due to
+          # issues other than failing to download dependencies (e.g., `cargo
+          # metadata` called with a malformed `Cargo.toml`, build failure in our
+          # own crate or in dependencies, etc). For those reasons, we discard
+          # stderr and ignore status codes.
+          #
+          # For downloading our crates' dependencies in particular, note that
+          # there is no support for doing this directly [1], so we just check
+          # all crates using --tests.
+          #
+          # [1]  https://stackoverflow.com/a/42139535/836390
+          cargo check --workspace --tests            &> /dev/null || true
+          cargo metadata                             &> /dev/null || true
+          cargo install cargo-readme --version 3.2.0 &> /dev/null || true
+          cargo install --locked kani-verifier       &> /dev/null || true
+          cargo kani setup                           &> /dev/null || true
+      shell: bash

.github/workflows/ci.yml

@@ -27,7 +27,6 @@ jobs:
     # first, most jobs would duplicate the work of downloading crates from
     # the internet. Populating the cache first ensures that this work only
     # happens once.
-    needs: generate_cache
 
     strategy:
       # By default, this is set to `true`, which means that a single CI job
@@ -73,12 +72,9 @@ jobs:
     steps:
     - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
-    - uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
-      with:
-        path: |
-          ~/.cargo/
-        key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
-
+    - name: Populate cache
+      uses: ./.github/actions/cache
+
     - name: Configure environment variables
       run: |
         set -eo pipefail
@@ -286,18 +282,14 @@ jobs:
           rustfmt --check zerocopy-derive/tests/**/*.rs
 
   check_readme:
-    needs: generate_cache
     runs-on: ubuntu-latest
     name: Check README.md
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
-      - uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
-        with:
-          path: |
-            ~/.cargo/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
-
+      - name: Populate cache
+        uses: ./.github/actions/cache
+
       - name: Check README.md
         run: |
           set -eo pipefail
@@ -311,18 +303,14 @@ jobs:
           exit $?
 
   check_msrv:
-    needs: generate_cache
     runs-on: ubuntu-latest
     name: Check MSRVs match
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
-
-      - uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
-        with:
-          path: |
-            ~/.cargo/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
-
+
+      - name: Populate cache
+        uses: ./.github/actions/cache
+
       # Make sure that the MSRV in zerocopy's and zerocopy-derive's `Cargo.toml`
       # files are the same. In CI, we test with a single MSRV (the one indicated
       # in zerocopy's `Cargo.toml`), so it's important that:
@@ -354,17 +342,13 @@ jobs:
           fi
 
   check_versions:
-    needs: generate_cache
     runs-on: ubuntu-latest
     name: Check crate versions match
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
 
-      - uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
-        with:
-          path: |
-            ~/.cargo/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
+      - name: Populate cache
+        uses: ./.github/actions/cache
 
       # Make sure that both crates are at the same version, and that zerocopy
       # depends exactly upon the current version of zerocopy-derive. See
@@ -432,40 +416,6 @@ jobs:
             "Same crate version ($zerocopy_derive_dep_ver) found for optional and targeted zerocopy-derive dependency." \
             "Different crate versions found for optional ($zerocopy_derive_dep_ver) and targeted ($zerocopy_derive_targeted_ver) dependency."
 
-  generate_cache:
-    runs-on: ubuntu-latest
-    name: Generate cache
-    steps:
-      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
-
-      - uses: actions/cache@13aacd865c20de90d75de3b17ebe84f7a17d57d2 # v4.0.0
-        with:
-          path: |
-            ~/.cargo/
-          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.toml') }}
-
-      - name: Populate cache
-        run: |
-          # Ensure all dependencies are downloaded - both for our crates and for
-          # tools we use in CI. We don't care about these tools succeeding for
-          # two reasons: First, this entire job is best-effort since it's just a
-          # performance optimization. Second, there may be failures due to
-          # issues other than failing to download dependencies (e.g., `cargo
-          # metadata` called with a malformed `Cargo.toml`, build failure in our
-          # own crate or in dependencies, etc). For those reasons, we discard
-          # stderr and ignore status codes.
-          #
-          # For downloading our crates' dependencies in particular, note that
-          # there is no support for doing this directly [1], so we just check
-          # all crates using --tests.
-          #
-          # [1]  https://stackoverflow.com/a/42139535/836390
-          cargo check --workspace --tests            &> /dev/null || true
-          cargo metadata                             &> /dev/null || true
-          cargo install cargo-readme --version 3.2.0 &> /dev/null || true
-          cargo install --locked kani-verifier       &> /dev/null || true
-          cargo kani setup                           &> /dev/null || true
-
   check-job-dependencies:
     runs-on: ubuntu-latest
     name: Check all-jobs-succeeded depends on all jobs
@@ -510,7 +460,7 @@ jobs:
       # https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
       if: failure()
       runs-on: ubuntu-latest
-      needs: [build_test, kani, check_fmt, check_readme, check_msrv, check_versions, generate_cache, check-job-dependencies]
+      needs: [build_test, kani, check_fmt, check_readme, check_msrv, check_versions, check-job-dependencies]
       steps:
         - name: Mark the job as failed
           run: exit 1