Implement 3 part MSRV policy (gfx-rs#8999)

cwfitzgerald · web-flow · commit 04746e747e24 · 2026-02-08T17:04:36.000-05:00
diff --git a/.github/workflows/changelog.yml b/.github/workflows/changelog.yml
@@ -18,7 +18,7 @@ env:
   # Dependency versioning
   #
 
-  # This is the MSRV used by `wgpu` itself and all surrounding infrastructure.
+  # This is the MSRV used by all repository infrastructure.
   REPO_MSRV: "1.93"
 
   #
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
@@ -18,11 +18,13 @@ env:
   # Dependency versioning
   #
 
-  # This is the MSRV used by `wgpu` itself and all surrounding infrastructure.
+  # This is the MSRV used by all repository infrastructure.
   REPO_MSRV: "1.93"
+  # This is the MSRV used by `wgpu` itself.
+  WGPU_MSRV: "1.87"
   # This is the MSRV used by the `wgpu-core`, `wgpu-hal`, and `wgpu-types` crates,
   # to ensure that they can be used with firefox.
-  CORE_MSRV: "1.90.0"
+  CORE_MSRV: "1.87"
 
   #
   # Environment variables
@@ -350,6 +352,83 @@ jobs:
                 --package wgpu \
                 --all-features --no-deps --document-private-items
 
+  # We run minimal checks on the MSRV of the `wgpu` crate, ensuring that
+  # its dependency tree does not cause issues for servo or other users.
+  #
+  # We don't test all platforms, just ones with different dependency stacks.
+  check-wgpu-msrv:
+    # runtime is normally 1-3 minutes
+    timeout-minutes: 10
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Windows
+          - name: Windows x86_64
+            os: windows-2022
+            target: x86_64-pc-windows-msvc
+
+          # MacOS
+          - name: MacOS x86_64
+            os: macos-14
+            target: x86_64-apple-darwin
+
+          # Linux
+          - name: Linux x86_64
+            os: ubuntu-24.04
+            target: x86_64-unknown-linux-gnu
+
+          # WebGPU
+          - name: WebAssembly
+            os: ubuntu-24.04
+            target: wasm32-unknown-unknown
+
+    name: wgpu MSRV Check ${{ matrix.name }}
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v6
+
+      - name: Install core MSRV toolchain
+        run: |
+          rustup toolchain install ${{ env.WGPU_MSRV }} --no-self-update --profile=minimal --component clippy --target ${{ matrix.target }}
+          rustup override set ${{ env.WGPU_MSRV }}
+          cargo -V
+
+      - name: Disable debug symbols
+        shell: bash
+        run: |
+          mkdir -p .cargo
+
+          cat <<EOF >> .cargo/config.toml
+            [profile.dev]
+            debug = false
+          EOF
+
+      - name: Caching
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: wgpu-msrv-check-${{ matrix.target }}-${{ env.CACHE_SUFFIX }}
+
+      - name: Reduce MSRV on dependencies
+        shell: bash
+        run: |
+          set -e
+
+          # No needed operations currently.
+          # If we find a dependency that needs to be downgraded to achieve
+          # the MSRV, we can do it here with `cargo update -p <crate> --precise <version>`
+
+      - name: Check native
+        shell: bash
+        run: |
+          set -e
+
+          # check `wgpu` with all features.
+          cargo check --target ${{ matrix.target }} --all-features -p wgpu
+
   # We run minimal checks on the MSRV of the core crates, ensuring that
   # its dependency tree does not cause issues for firefox.
   #
@@ -377,7 +456,7 @@ jobs:
             os: ubuntu-24.04
             target: x86_64-unknown-linux-gnu
 
-    name: MSRV Check ${{ matrix.name }}
+    name: Core MSRV Check ${{ matrix.name }}
     runs-on: ${{ matrix.os }}
 
     steps:
@@ -403,17 +482,16 @@ jobs:
       - name: Caching
         uses: Swatinem/rust-cache@v2
         with:
-          key: msrv-check-${{ matrix.target }}-${{ env.CACHE_SUFFIX }}
+          key: core-msrv-check-${{ matrix.target }}-${{ env.CACHE_SUFFIX }}
 
       - name: Reduce MSRV on dependencies
         shell: bash
         run: |
           set -e
 
-          # 1.23.2 requires bytemuck_derive 1.10.1
-          cargo update -p bytemuck --precise 1.23.1
-          # 1.9.0 requires MSRV 1.84
-          cargo update -p bytemuck_derive --precise 1.8.1
+          # No needed operations currently.
+          # If we find a dependency that needs to be downgraded to achieve
+          # the MSRV, we can do it here with `cargo update -p <crate> --precise <version>`
 
       - name: Check native
         shell: bash
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
@@ -14,7 +14,7 @@ on:
   merge_group:
 
 env:
-  # This is the MSRV used by `wgpu` itself and all surrounding infrastructure.
+  # This is the MSRV used by all repository infrastructure.
   REPO_MSRV: "1.93"
 
   CARGO_INCREMENTAL: false
diff --git a/.github/workflows/generate.yml b/.github/workflows/generate.yml
@@ -18,8 +18,8 @@ env:
   # Dependency versioning
   #
 
-  # This is the MSRV used by `wgpu` itself and all surrounding infrastructure.
-  REPO_MSRV: "1.93"
+  # This is the MSRV used by `wgpu` itself.
+  WGPU_MSRV: "1.87"
   RUSTFLAGS: -D warnings
 
 # Every time a PR is pushed to, cancel any previous jobs. This
@@ -55,7 +55,7 @@ jobs:
       # the toolchain for the current directory, not the newly generated project.
       - name: Install repo MSRV toolchain
         run: |
-          rustup toolchain install ${{ env.REPO_MSRV }} --no-self-update --profile=minimal
+          rustup toolchain install ${{ env.WGPU_MSRV }} --no-self-update --profile=minimal
           cargo -V
 
       - name: Disable debug symbols
@@ -90,4 +90,4 @@ jobs:
             [patch.crates-io]
             wgpu = { path = "../wgpu/wgpu" }
           EOF
-          cargo +${{ env.REPO_MSRV }} check
+          cargo +${{ env.WGPU_MSRV }} check
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -42,6 +42,12 @@ Bottom level categories:
 
 ## Unreleased
 
+### Major Changes
+
+`wgpu` now has a new MSRV policy. This release has an MSRV of **1.87**. This is lower than v27's 1.88 and v28's 1.92. Going forward, we will only bump wgpu's MSRV if it has tangible benefits for the code, and we will never bump to an MSRV higher than `stable - 3`. So if stable is at 1.97 and 1.94 brought benefit to our code, we could bump it no higher than 1.94. As before, MSRV bumps will always be breaking changes. 
+
+By @cwfitzgerald in [#8999](https://github.com/gfx-rs/wgpu/pull/8999).
+
 ### New Features
 
 #### General
diff --git a/README.md b/README.md
@@ -96,25 +96,35 @@ For an overview of all the components in the gfx-rs ecosystem, see [the big pict
 
 ## MSRV policy
 
-TL;DR: If you're using `wgpu`, our MSRV is **1.93**.
+TL;DR: If you're using `wgpu`, our MSRV is **1.87**. If you're running our tests or examples, our MSRV is **1.93**.
+
+We will avoid bumping the MSRV of `wgpu` without good reason, and such a change is considered breaking.
 
 <details>
 <summary> Specific Details </summary>
 
-Due to complex dependants, we have two MSRV policies:
+Due to complex dependants, we have three MSRV policies:
 
-- `naga`, `wgpu-core`, `wgpu-hal`, and `wgpu-types`'s MSRV is **1.90**.
+- `wgpu`'s MSRV is **1.87**
+- `wgpu-core` (and hence `wgpu-hal`, `naga`, and `wgpu-types`)'s MSRV is **1.87**.
 - The rest of the workspace has an MSRV of **1.93**.
 
-It is enforced on CI (in "/.github/workflows/ci.yml") with the `CORE_MSRV` and `REPO_MSRV` variables.
+It is enforced on CI (in "/.github/workflows/ci.yml") with the `WGPU_MSRV`, `CORE_MSRV`, and `REPO_MSRV` variables, respectively.
 This version can only be upgraded in breaking releases, though we release a breaking version every three months.
 
-The `naga`, `wgpu-core`, `wgpu-hal`, and `wgpu-types` crates should never
-require an MSRV ahead of Firefox's MSRV for nightly builds, as
-determined by the value of `MINIMUM_RUST_VERSION` in
-[`python/mozboot/mozboot/util.py`][util].
-
-[util]: https://searchfox.org/mozilla-central/source/python/mozboot/mozboot/util.py
+The following rules apply:
+- The `wgpu-core` crate should never require an MSRV ahead of Firefox's MSRV for nightly builds, as
+determined by the value of `MINIMUM_RUST_VERSION` in [`python/mozboot/mozboot/util.py`][moz-msrv].
+- The `wgpu` crate should never require an MSRV ahead of Servo's MSRV, as determined by the value of
+their rust-version declaration in [`Cargo.toml`][servo-msrv]
+- The repository MSRV should never require an MSRV higher than `stable - 3`. For example, if stable is
+at 1.97, the repository MSRV should be no higher than 1.94. This is to allow people who are using a decently-updated
+OS-provided rust to be able to build our repository. Consider cross checking with [NixOS][nixos-msrv], though this
+is not required.
+
+[moz-msrv]: https://searchfox.org/mozilla-central/source/python/mozboot/mozboot/util.py
+[servo-msrv]: https://github.com/servo/servo/blob/main/Cargo.toml#L23
+[nixos-msrv]: https://search.nixos.org/packages?show=rustc
 
 </details>
 
diff --git a/examples/standalone/01_hello_compute/Cargo.toml b/examples/standalone/01_hello_compute/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "wgpu-example-01-hello-compute"
 edition = "2021"
-rust-version = "1.93"
+rust-version = "1.87"
 publish = false
 
 [dependencies]
diff --git a/examples/standalone/02_hello_window/Cargo.toml b/examples/standalone/02_hello_window/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "wgpu-example-02-hello-window"
 edition = "2021"
-rust-version = "1.93"
+rust-version = "1.87"
 publish = false
 
 [dependencies]
diff --git a/examples/standalone/custom_backend/Cargo.toml b/examples/standalone/custom_backend/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "wgpu-example-custom-backend"
 edition = "2021"
-rust-version = "1.93"
+rust-version = "1.87"
 publish = false
 
 [features]
diff --git a/naga/Cargo.toml b/naga/Cargo.toml
@@ -13,7 +13,7 @@ exclude = ["bin/**/*", "tests/**/*", "Cargo.lock", "target/**/*"]
 # copy the crates it actually uses out of the workspace, so it's meaningful for
 # them to have less restrictive MSRVs individually than the workspace as a
 # whole, if their code permits. See `../README.md` for details.
-rust-version = "1.90.0"
+rust-version = "1.87"
 
 [package.metadata.docs.rs]
 all-features = true
diff --git a/wgpu-core/Cargo.toml b/wgpu-core/Cargo.toml
@@ -9,11 +9,11 @@ repository.workspace = true
 keywords.workspace = true
 license.workspace = true
 
-# Override the workspace's `rust-version` key. Firefox uses `cargo vendor` to
-# copy the crates it actually uses out of the workspace, so it's meaningful for
-# them to have less restrictive MSRVs individually than the workspace as a
-# whole, if their code permits. See `../README.md` for details.
-rust-version = "1.90.0"
+# Override the workspace's `rust-version` key. `wgpu-core` and its dependencies
+# have a less strict MSRV, to allow firefox more leeway in updating their Rust toolchain.
+#
+# See the repo README for more information on MSRV policy.
+rust-version = "1.87"
 
 [package.metadata.docs.rs]
 all-features = true
diff --git a/wgpu-hal/Cargo.toml b/wgpu-hal/Cargo.toml
@@ -9,11 +9,11 @@ repository.workspace = true
 keywords.workspace = true
 license.workspace = true
 
-# Override the workspace's `rust-version` key. Firefox uses `cargo vendor` to
-# copy the crates it actually uses out of the workspace, so it's meaningful for
-# them to have less restrictive MSRVs individually than the workspace as a
-# whole, if their code permits. See `../README.md` for details.
-rust-version = "1.90.0"
+# Override the workspace's `rust-version` key. `wgpu-core` and its dependencies
+# have a less strict MSRV, to allow firefox more leeway in updating their Rust toolchain.
+#
+# See the repo README for more information on MSRV policy.
+rust-version = "1.87"
 
 [package.metadata.docs.rs]
 # Ideally we would enable all the features.
diff --git a/wgpu-types/Cargo.toml b/wgpu-types/Cargo.toml
@@ -9,11 +9,11 @@ repository.workspace = true
 keywords.workspace = true
 license.workspace = true
 
-# Override the workspace's `rust-version` key. Firefox uses `cargo vendor` to
-# copy the crates it actually uses out of the workspace, so it's meaningful for
-# them to have less restrictive MSRVs individually than the workspace as a
-# whole, if their code permits. See `../README.md` for details.
-rust-version = "1.90.0"
+# Override the workspace's `rust-version` key. `wgpu-core` and its dependencies
+# have a less strict MSRV, to allow firefox more leeway in updating their Rust toolchain.
+#
+# See the repo README for more information on MSRV policy.
+rust-version = "1.87"
 
 [package.metadata.docs.rs]
 all-features = true
diff --git a/wgpu/Cargo.toml b/wgpu/Cargo.toml
@@ -8,10 +8,15 @@ homepage.workspace = true
 repository.workspace = true
 keywords.workspace = true
 license.workspace = true
-rust-version.workspace = true
 readme = "../README.md"
 exclude = ["Cargo.lock"]
 
+# Override the workspace's `rust-version` key. `wgpu` and its dependencies
+# have a less strict MSRV, to allow users more leeway in updating their Rust toolchain.
+#
+# See the repo README for more information on MSRV policy.
+rust-version = "1.87.0"
+
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
diff --git a/wgpu/src/lib.rs b/wgpu/src/lib.rs
@@ -28,7 +28,7 @@
 //! | --------------------- | ---------------------- |
 //! | ![render_coordinates] | ![texture_coordinates] |
 //!
-//! `wgpu`'s MSRV is **1.93**.
+//! `wgpu`'s MSRV is **1.87**.
 //!
 //! [Learn Wgpu]: https://sotrh.github.io/learn-wgpu/
 //! [WebGPU Fundamentals]: https://webgpufundamentals.org/

Original file line number	Diff line number	Diff line change
`@@ -18,7 +18,7 @@ env:`
`18`	`18`	`# Dependency versioning`
`19`	`19`	`#`
`20`	`20`
`21`		- # This is the MSRV used by `wgpu` itself and all surrounding infrastructure.
	`21`	`+ # This is the MSRV used by all repository infrastructure.`
`22`	`22`	`REPO_MSRV: "1.93"`
`23`	`23`
`24`	`24`	`#`