Remove schemars pinning

Pinning was introduced using `<=` in the version number for `schemars`
and `dyn-clone`, we would prefer to use pinning by way of the
`cargo update -p`.

- Remove the pinning from `Cargo.toml`.
- Add pinning to CI
- Document pinning in readme

Cargo.toml

@@ -14,7 +14,7 @@ edition = "2018"
 [features]
 default = ["std"]
 std = []
-schemars = ["actual-schemars", "dyn-clone"]
+schemars = ["actual-schemars"]
 # If you disable std, you can still use a Write trait via the core2 feature.
 # You can also use ToHex via the alloc feature, as it requires Vec/String.
 # And you can still just disable std by disabling default features, without enabling these two.
@@ -29,10 +29,7 @@ serde = { version = "1.0", default-features = false, optional = true }
 core2 = { version = "0.3.0", optional = true, default_features = false }
 
 # Do NOT use this as a feature! Use the `schemars` feature instead. Can only be used with "std" enabled.
-actual-schemars = { package = "schemars", version = "<=0.8.3", optional = true }
-# Do NOT enable this dependency, this is just to pin dyn-clone (transitive dep from schemars)
-# because 1.0.8 does not build with Rust 1.41.1 (because of useage of `Arc::as_ptr`).
-dyn-clone = { version = "<=1.0.7", default_features = false, optional = true }
+actual-schemars = { package = "schemars", version = "0.8.3", optional = true }
 
 [dev-dependencies]
 serde_test = "1.0"

README.md

@@ -13,6 +13,16 @@ since these are needed to display hashes anway.
 
 This library should always compile with any combination of features on **Rust 1.41.1**.
 
+### Dependency pinning
+
+Some dependencies break the MSRV build (only when building with `schemars` feature), to build with
+Rust 1.41.1 you need to pin as follows:
+```bash
+
+    cargo update --package schemars --precise 0.8.3
+    cargo update --package dyn-clone --precise 1.0.7
+```
+
 ## Contributions
 
 Contributions are welcome, including additional hash function implementations.

contrib/test.sh

@@ -16,6 +16,12 @@ export CARGO_TERM_VERBOSE=true
 cargo build --all
 cargo test --all
 
+# Pin if using MSRV toolchain.
+if cargo --version | grep "cargo 1\.41"; then
+    cargo update --package schemars --precise 0.8.3
+    cargo update --package dyn-clone --precise 1.0.7
+fi
+
 if [ "$DO_FEATURE_MATRIX" = true ]; then
     cargo build --all --no-default-features
     cargo test --all --no-default-features

extended_tests/schemars/Cargo.toml

@@ -12,6 +12,6 @@ features = ['schemars', 'serde']
 [dependencies]
 jsonschema-valid = "^0.4.0"
 serde = { version = "1.0", default-features = false}
-schemars = { version = "<=0.8.3"}
+schemars = { version = "0.8.3"}
 serde_test = "1.0"
 serde_json = "1.0"