chore(ci): implement smart test caching with just across all languages

Author: markkovari

.github/workflows/tests.yml

@@ -87,13 +87,21 @@ jobs:
         if: ${{ matrix.project == '2021/_4' }}
       - name: Set up cargo-nextest
         uses: taiki-e/install-action@nextest
+      - name: Install just
+        uses: taiki-e/install-action@just
+      - name: Restore cache
+        uses: actions/cache@v4
+        with:
+          path: .cache
+          key: ${{ runner.os }}-rust-cache-${{ hashFiles('**/Cargo.lock', 'aoc-rust-common/src/**') }}-${{ matrix.project }}
+          restore-keys: |
+            ${{ runner.os }}-rust-cache-
       - name: Run Clippy
         run: cargo clippy --workspace -- -A warnings
         working-directory: ${{ matrix.project }}
         continue-on-error: true
       - name: Run Rust tests
-        run: cargo test
-        working-directory: ${{ matrix.project }}
+        run: just test-project-rust ${{ matrix.project }}
         env:
           RUSTFLAGS: --cfg advent_of_code_ci
 
@@ -112,9 +120,17 @@ jobs:
         with:
           go-version: '1.22.x'
           cache: false
+      - name: Install just
+        uses: taiki-e/install-action@just
+      - name: Restore cache
+        uses: actions/cache@v4
+        with:
+          path: .cache
+          key: ${{ runner.os }}-go-cache-${{ hashFiles('**/go.mod', 'aoc-go-common/**') }}-${{ matrix.project }}
+          restore-keys: |
+            ${{ runner.os }}-go-cache-
       - name: Run Go tests
-        run: go test ./...
-        working-directory: ${{ matrix.project }}
+        run: just test-project-go ${{ matrix.project }}
 
   zig_tests:
     needs: detect_changes
@@ -130,7 +146,15 @@ jobs:
         uses: goto-bus-stop/setup-zig@v2
         with:
           version: 0.14.0
+      - name: Install just
+        uses: taiki-e/install-action@just
+      - name: Restore cache
+        uses: actions/cache@v4
+        with:
+          path: .cache
+          key: ${{ runner.os }}-zig-cache-${{ matrix.project }}
+          restore-keys: |
+            ${{ runner.os }}-zig-cache-
       - name: Run Zig tests
-        run: zig build test
-        working-directory: ${{ matrix.project }}
+        run: just test-project-zig ${{ matrix.project }}
         continue-on-error: true

.gitignore

@@ -3,3 +3,4 @@
 .gemini/
 gha-creds-*.json
 target/
+.cache/

justfile

@@ -0,0 +1,76 @@
+set shell := ["bash", "-c"]
+
+# Run all tests across all languages
+test-all:
+    just test-rust
+    just test-go
+    just test-zig
+
+# --- Rust ---
+
+# Run all Rust tests
+test-rust:
+    @for project in 2015 2018 2019/aoc_rust 2020/01 2021/_1 2021/_2 2021/_3 2021/_4 2021/_5 2021/_6 2021/_7 2022 2023/rust 2025/rust runner; do \
+        just test-project-rust $project; \
+    done
+
+# Run a specific Rust project if its files or aoc-rust-common changed
+test-project-rust project:
+    @mkdir -p .cache/rust
+    @SAFE_NAME=$(echo {{project}} | tr '/' '_')
+    @# Hash the project dir AND the shared rust library
+    @HASH=$(find {{project}} aoc-rust-common -type f -not -path "*/target/*" -not -path "*/.git/*" 2>/dev/null | sort | xargs shasum -a 256 | shasum -a 256 | awk '{print $1}')
+    @if [ -z "$HASH" ]; then HASH="empty"; fi
+    @if [ -f .cache/rust/$SAFE_NAME.success ] && [ "$(cat .cache/rust/$SAFE_NAME.success)" = "$HASH" ]; then \
+        echo "✅ Rust: {{project}} (Cached)"; \
+    else \
+        echo "🚀 Rust: Running {{project}}..."; \
+        (cd {{project}} && cargo test) && echo "$HASH" > .cache/rust/$SAFE_NAME.success; \
+    fi
+
+# --- Go ---
+
+# Run all Go tests
+test-go:
+    @for project in 2017 2019/go 2020/02 2024/golang; do \
+        just test-project-go $project; \
+    done
+
+# Run a specific Go project if its files or aoc-go-common changed
+test-project-go project:
+    @mkdir -p .cache/go
+    @SAFE_NAME=$(echo {{project}} | tr '/' '_')
+    @# Hash the project dir AND the shared go library
+    @HASH=$(find {{project}} aoc-go-common -type f -not -path "*/.git/*" 2>/dev/null | sort | xargs shasum -a 256 | shasum -a 256 | awk '{print $1}')
+    @if [ -z "$HASH" ]; then HASH="empty"; fi
+    @if [ -f .cache/go/$SAFE_NAME.success ] && [ "$(cat .cache/go/$SAFE_NAME.success)" = "$HASH" ]; then \
+        echo "✅ Go: {{project}} (Cached)"; \
+    else \
+        echo "🚀 Go: Running {{project}}..."; \
+        (cd {{project}} && go test ./...) && echo "$HASH" > .cache/go/$SAFE_NAME.success; \
+    fi
+
+# --- Zig ---
+
+# Run all Zig tests
+test-zig:
+    @for project in 2021/zig 2024/zig; do \
+        just test-project-zig $project; \
+    done
+
+# Run a specific Zig project if its files changed
+test-project-zig project:
+    @mkdir -p .cache/zig
+    @SAFE_NAME=$(echo {{project}} | tr '/' '_')
+    @HASH=$(find {{project}} -type f -not -path "*/.zig-cache/*" -not -path "*/zig-out/*" -not -path "*/.git/*" 2>/dev/null | sort | xargs shasum -a 256 | shasum -a 256 | awk '{print $1}')
+    @if [ -z "$HASH" ]; then HASH="empty"; fi
+    @if [ -f .cache/zig/$SAFE_NAME.success ] && [ "$(cat .cache/zig/$SAFE_NAME.success)" = "$HASH" ]; then \
+        echo "✅ Zig: {{project}} (Cached)"; \
+    else \
+        echo "🚀 Zig: Running {{project}}..."; \
+        (cd {{project}} && zig build test) && echo "$HASH" > .cache/zig/$SAFE_NAME.success; \
+    fi
+
+# Clean all test caches
+clean-cache:
+    rm -rf .cache