credentials: Do not test MSRVs that depend on Serde's MSRVs

Serde's MSRV is no longer stable.

.github/workflows/ci.yml

@@ -149,22 +149,11 @@ jobs:
  toolchain:
  - '1.0.0'
  - '1.6.0'
- - '1.8.0'
- - '1.13.0'
  - '1.36.0'
  include:
  - toolchain: '1.0.0'
  features: std
- # Toolchains older than 1.8.0 cannot compile `oauth-credentials` directly
- # because the toolchains do not understand Cargo registry's information for `serde`
- # (see <https://github.com/rust-lang/cargo/issues/3763>).
- # So, with these toolchains, we compile a crate named `oauth-credentials-test` instead,
- # which depends on `oauth-credentials` without `serde` feature.
- crate_suffix: '-test'
  - toolchain: '1.6.0'
- crate_suffix: '-test'
- - toolchain: '1.13.0'
- features: serde
  - toolchain: '1.36.0'
  features: alloc
  steps:
@@ -195,7 +184,12 @@ jobs:
  uses: actions-rs/cargo@v1
  with:
  command: build
- args: --verbose --manifest-path oauth-credentials${{ matrix.crate_suffix }}/Cargo.toml --no-default-features --features=${{ matrix.features }}
+ # Toolchains older than 1.8.0 cannot compile `oauth-credentials` directly
+ # because the toolchains do not understand Cargo registry's information for `serde`
+ # (see <https://github.com/rust-lang/cargo/issues/3763>).
+ # So, with these toolchains, we instead build a dependant crate of `oauth-credentials`
+ # without `serde` feature.
+ args: --verbose --manifest-path oauth-credentials-test/Cargo.toml --no-default-features --features=${{ matrix.features }}
  credentials-test:
  name: Test `oauth-credentials`
  runs-on: ubuntu-latest

oauth-credentials-test/Cargo.toml

@@ -2,7 +2,7 @@
 name = "oauth-credentials-test"
 version = "0.0.0"
 authors = ["Daiki Mizukami <[email protected]>"]
-description = "A hack to make the CI work for Rust 1.7.0 and older."
+description = "A hack to make the CI work with older toolchains."
 publish = false
 
 [dependencies]

oauth-credentials/README.md

@@ -38,12 +38,13 @@ Feature | MSRV
 -|-
 (none) | 1.6.0
 `std` (default) | 1.0.0
-`serde` |  1.13.0
+`serde` | (See [Serde's `rust-version`][serde-cargo-toml])
 `alloc` (without `std`) | 1.36.0
 
 Note that if your crate uses the `serde` feature (even if optionally!), it
 cannot be compiled directly with Rust 1.7.x and older due to
 [rust-lang/cargo#3763], but it can somehow be compiled as a dependency of
 another crate if the feature is disabled.
 
+[serde-cargo-toml]: https://docs.rs/crate/serde/latest/source/Cargo.toml.orig
 [rust-lang/cargo#3763]: https://github.com/rust-lang/cargo/issues/3763