Add a minimal-versions check

.github/workflows/check.yml

@@ -77,3 +77,32 @@ jobs:
       with:
         token: ${{ secrets.GITHUB_TOKEN }}
         args: --all --examples --tests --benches -- -D warnings
+
+  minimal-versions:
+    # Check for minimal-versions errors where a dependency is too
+    # underconstrained to build on the minimal supported version of all
+    # dependencies in the dependency graph.
+    name: minimal-versions
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: nightly
+          profile: minimal
+          override: true
+      - name: Install cargo-hack
+        run: |
+          curl -LsSf https://github.com/taiki-e/cargo-hack/releases/latest/download/cargo-hack-x86_64-unknown-linux-gnu.tar.gz | tar xzf - -C ~/.cargo/bin
+      - name: "check --all-features -Z minimal-versions"
+        run: |
+          # Remove dev-dependencies from Cargo.toml to prevent the next `cargo update`
+          # from determining minimal versions based on dev-dependencies.
+          cargo hack --remove-dev-deps --workspace
+          # Update Cargo.lock to minimal version dependencies.
+          cargo update -Z minimal-versions
+          cargo hack check \
+            --package tracing \
+            --package tracing-core \
+            --package tracing-subscriber \
+            --all-features --ignore-private

tracing-core/Cargo.toml

@@ -35,7 +35,7 @@ std = ["lazy_static", "alloc"]
 maintenance = { status = "actively-developed" }
 
 [dependencies]
-lazy_static = { version = "1", optional = true }
+lazy_static = { version = "1.0.2", optional = true }
 
 [package.metadata.docs.rs]
 all-features = true

tracing-subscriber/Cargo.toml

@@ -57,7 +57,7 @@ serde = { version = "1.0", optional = true }
 tracing-serde = { path = "../tracing-serde", version = "0.2", optional = true }
 
 # opt-in deps
-parking_lot = { version = ">= 0.7, <= 0.12", optional = true }
+parking_lot = { version = ">= 0.9.0, <= 0.12", optional = true }
 
 # registry
 sharded-slab = { version = "0.1.0", optional = true }