doc: document derive_use_cargo feature

borsh-derive/src/lib.rs

@@ -73,20 +73,28 @@ Attribute takes literal string value, which is the syn's [Path] to `borsh` crate
 
 Attribute is optional.
 
-1. If the attribute is not provided, [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
-in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+1. If the attribute is not provided:
 
-```bash
- 1  error: proc-macro derive panicked
-   --> path/to/file.rs:27:10
-    |
- 27 | #[derive(BorshSerialize, BorshDeserialize)]
-    |          ^^^^^^^^^^^^^^
-    |
-    = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
-```
+  - If `proc-macro-crate` feature of `borsh-derive`, which is controlled by `derive_use_cargo` feature 
+    of `borsh`, is enabled, then
+    [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
+    in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+
+    ```bash
+     1  error: proc-macro derive panicked
+       --> path/to/file.rs:27:10
+        |
+     27 | #[derive(BorshSerialize, BorshDeserialize)]
+        |          ^^^^^^^^^^^^^^
+        |
+        = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
+    ```
+
+  - If `proc-macro-crate` feature of `borsh-derive` is disabled, the path to `borsh` is assumed to be simply `borsh`.  
+    The feature can be opted out of to remove dependency on `cargo` in build process.
 
-2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped.
+2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped
+   and the provided attribute value is used instead.
 
 Examples of usage:
 
@@ -360,20 +368,28 @@ Attribute takes literal string value, which is the syn's [Path] to `borsh` crate
 
 Attribute is optional.
 
-1. If the attribute is not provided, [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
-in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+1. If the attribute is not provided:
 
-```bash
- 1  error: proc-macro derive panicked
-   --> path/to/file.rs:27:10
-    |
- 27 | #[derive(BorshDeserialize, BorshSerialize)]
-    |          ^^^^^^^^^^^^^^^^
-    |
-    = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
-```
+  - If `proc-macro-crate` feature of `borsh-derive`, which is controlled by `derive_use_cargo` feature 
+    of `borsh`, is enabled, then
+    [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
+    in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+
+    ```bash
+     1  error: proc-macro derive panicked
+       --> path/to/file.rs:27:10
+        |
+     27 | #[derive(BorshDeserialize, BorshSerialize)]
+        |          ^^^^^^^^^^^^^^^^
+        |
+        = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
+    ```
 
-2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped.
+  - If `proc-macro-crate` feature of `borsh-derive` is disabled, the path to `borsh` is assumed to be simply `borsh`.  
+    The feature can be opted out of to remove dependency on `cargo` in build process.
+
+2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped
+   and the provided attribute value is used instead.
 
 Examples of usage:
 
@@ -696,20 +712,28 @@ Attribute takes literal string value, which is the syn's [Path] to `borsh` crate
 
 Attribute is optional.
 
-1. If the attribute is not provided, [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
-in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+1. If the attribute is not provided:
 
-```bash
- 1  error: proc-macro derive panicked
-   --> path/to/file.rs:27:10
-    |
- 27 | #[derive(BorshSchema, BorshSerialize)]
-    |          ^^^^^^^^^^^
-    |
-    = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
-```
+  - If `proc-macro-crate` feature of `borsh-derive`, which is controlled by `derive_use_cargo` feature 
+    of `borsh`, is enabled, then
+    [crate_name](proc_macro_crate::crate_name) is used to find a version of `borsh`
+    in `[dependencies]` of the relevant `Cargo.toml`. If there is no match, a compilation error, similar to the following, is raised:
+
+    ```bash
+     1  error: proc-macro derive panicked
+       --> path/to/file.rs:27:10
+        |
+     27 | #[derive(BorshSchema, BorshSerialize)]
+        |          ^^^^^^^^^^^
+        |
+        = help: message: called `Result::unwrap()` on an `Err` value: CrateNotFound { crate_name: "borsh", path: "/path/to/Cargo.toml" }
+    ```
+
+  - If `proc-macro-crate` feature of `borsh-derive` is disabled, the path to `borsh` is assumed to be simply `borsh`.  
+    The feature can be opted out of to remove dependency on `cargo` in build process.
 
-2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped.
+2. If the attribute is provided, the check for `borsh` in `[dependencies]` of the relevant `Cargo.toml` is skipped
+   and the provided attribute value is used instead.
 
 Examples of usage:
 

borsh/src/lib.rs

@@ -20,13 +20,19 @@
 
 ### Default features
 
-* **std** - enabled by default.
+* **std** , **derive_use_cargo** - enabled by default.
 
 ### Other features
 
 * **derive** -
   Gates derive macros of [BorshSerialize] and
   [BorshDeserialize] traits.
+* **derive_use_cargo** -
+  Enables `proc-macro-crate` feature of `borsh-derive` dependency, which tracks `borsh`
+  crate rename in `Cargo.toml` via `cargo`. 
+
+  This feature has effect only if **derive** feature  is enabled.
+  More details are mentioned in `#[borsh(crate = ...)]` attribute description in [borsh_derive] doc.
 * **unstable__schema** -
   Gates [BorshSchema] trait and its derive macro.
   Gates [schema] module.