feat(ci): Add zepter for feature propagation checks

.config/zepter.yaml

@@ -0,0 +1,39 @@
+version:
+  format: 1
+  # Minimum zepter version that is expected to work. This is just for printing a nice error
+  # message when someone tries to use an older version.
+  binary: 0.13.2
+
+# The examples in the following comments assume crate `A` to have a dependency on crate `B`.
+workflows:
+  check:
+    - [
+        "lint",
+        # Check that `A` activates the features of `B`.
+        "propagate-feature",
+        # These are the features to check:
+        "--features=64-bit,m,a,c,test-utils",
+        # Do not try to add a new section into `[features]` of `A` only because `B` exposes that feature. There are edge-cases where this is still needed, but we can add them manually.
+        "--left-side-feature-missing=ignore",
+        # Ignore the case that `A` is outside of the workspace. Otherwise it will report errors in external dependencies that we have no influence on.
+        "--left-side-outside-workspace=ignore",
+        # Only check normal dependencies.
+        # Propagating to dev-dependencies leads to compilation issues.
+        "--dep-kinds=normal:check,dev:ignore",
+        "--show-path",
+        "--quiet",
+      ]
+  default:
+    # Running `zepter` with no subcommand will check & fix.
+    - [$check.0, "--fix"]
+
+# Will be displayed when any workflow fails:
+help:
+  text: |
+    Brisc uses the Zepter CLI to detect abnormalities in Cargo features, e.g. missing propagation.
+
+    It looks like one more checks failed; please check the console output.
+
+    You can try to automatically address them by installing zepter (`cargo install zepter --locked`) and simply running `zepter` in the workspace root.
+  links:
+    - "https://github.com/ggwpez/zepter"

.github/workflows/rust_ci.yaml

@@ -168,3 +168,20 @@ jobs:
         uses: codecov/test-results-action@v1
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
+
+  zepter:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: true
+      - name: Install zepter
+        run: |
+          cargo install zepter -f --locked
+          zepter --version
+      - name: Format features
+        run: |
+          zepter format features
+      - name: Lint features
+        run: |
+          zepter

crates/emu/Cargo.toml

@@ -27,14 +27,14 @@ rstest.workspace = true
 criterion.workspace = true
 
 [features]
-default = ["64-bit", "m", "a", "c"]
-test-utils = ["dep:rstest"]
+default = [ "64-bit", "a", "c", "m" ]
+test-utils = [ "dep:rstest" ]
 
 # Architecture features
-64-bit = ["brisc-hw/64-bit"]
-m = ["brisc-hw/m"]
-a = ["brisc-hw/a"]
-c = ["brisc-hw/c"]
+64-bit = [ "brisc-hw/64-bit" ]
+m = [ "brisc-hw/m" ]
+a = [ "brisc-hw/a" ]
+c = [ "brisc-hw/c" ]
 
 [[bench]]
 harness = false

crates/hw/Cargo.toml

@@ -25,10 +25,10 @@ cfg-if.workspace = true
 rstest.workspace = true
 
 [features]
-default = ["64-bit", "m", "a", "c"]
+default = [ "64-bit", "a", "c", "m" ]
 
 # Architecture features
-64-bit = ["brisc-isa/64-bit"]
-m = ["brisc-isa/m"]
-a = ["brisc-isa/a"]
-c = ["brisc-isa/c"]
+64-bit = [ "brisc-isa/64-bit" ]
+m = [ "brisc-isa/m" ]
+a = [ "brisc-isa/a" ]
+c = [ "brisc-isa/c" ]

crates/isa/Cargo.toml

@@ -21,7 +21,7 @@ num-traits.workspace = true
 rstest.workspace = true
 
 [features]
-default = ["64-bit", "m", "a", "c"]
+default = [ "64-bit", "a", "c", "m" ]
 64-bit = []
 m = []
 a = []