Fix Cargo offline handling in CI tests

Author: An Zhong

.github/workflows/test.yaml

@@ -12,6 +12,8 @@ jobs:
   test:
     name: Test
     runs-on: self-hosted
+    env:
+      CARGO_HOME: ${{ github.workspace }}/.cargo-home
     steps:
       - uses: actions/checkout@v4
         with:
@@ -22,6 +24,16 @@ jobs:
           toolchain: stable
           components: rustfmt, clippy
           override: true
+
+      - name: Cache Cargo Dependencies
+        uses: actions/cache@v4
+        with:
+          path: |
+            .cargo-home/registry
+            .cargo-home/git
+          key: ${{ runner.os }}-cargo-${{ hashFiles('tools/rust-sim-runtime/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
       
       - name: Apply Patches
         run: |
@@ -34,12 +46,18 @@ jobs:
           echo "verilator-hash=$(git rev-parse HEAD:3rd-party/verilator)" >> $GITHUB_OUTPUT
           echo "ramulator2-hash=$(git rev-parse HEAD:3rd-party/ramulator2)" >> $GITHUB_OUTPUT
 
+      - name: Prefetch Rust Dependencies
+        run: |
+          . setup.sh && cargo fetch --manifest-path tools/rust-sim-runtime/Cargo.toml --locked
+
       - name: Build All Components
         run: |
           echo "Building all components"
           . setup.sh && make build-all
       
       - name: Run All Tests
+        env:
+          ASSASSYN_CARGO_NET_OFFLINE: "1"
         run: |
           . setup.sh && make test-all
 

python/assassyn/utils/__init__.py

@@ -86,11 +86,8 @@ def _cmd_wrapper(cmd):
             os.makedirs(ccache_dir, exist_ok=True)
             env['CCACHE_DIR'] = ccache_dir
 
-    # In CI / sandboxed runners, network access may be restricted. If tests are
-    # running, prefer offline to avoid Cargo trying to touch crates.io.
-    if 'CARGO_NET_OFFLINE' not in env and (
-        'PYTEST_CURRENT_TEST' in env or env.get('ASSASSYN_CARGO_NET_OFFLINE') == '1'
-    ):
+    # Only force Cargo offline when CI or the caller opts in explicitly.
+    if 'CARGO_NET_OFFLINE' not in env and env.get('ASSASSYN_CARGO_NET_OFFLINE') == '1':
         env['CARGO_NET_OFFLINE'] = 'true'
 
     return subprocess.check_output(cmd, env=env).decode('utf-8')