Support for parsing a list of schemas which may have cross dependenci…

…es (#173)

* Added ability to parse a list of schemas, which may have cross dependencies. Added tests

* Fixing the formatting

* A bit more formatting

* Added a comma to please clippy

* Switched an ok_or to an ok_or_else at the behest of clippy

* Following fixes: Fixed some docstrings, a new error for name collisions when using parse_list, guarantees that input order matches output order

* Removed an unused import

* Small formatting fixes

* Added another test involving fullnames

* Added test that ensures when a recursive type is put in, the algorithm does blow the top off the stack but returns an error

* removed unused variable

* Updated readme and one tiny fix

README.md

@@ -86,6 +86,38 @@ let schema = Schema::parse_str(raw_schema).unwrap();
 println!("{:?}", schema);
 ```
 
+Additionally, a list of of definitions (which may depend on each other) can be given and all of
+them will be parsed into the corresponding schemas.
+
+```rust
+use avro_rs::Schema;
+
+let raw_schema_1 = r#"{
+        "name": "A",
+        "type": "record",
+        "fields": [
+            {"name": "field_one", "type": "float"}
+        ]
+    }"#;
+
+// This definition depends on the definition of A above
+let raw_schema_2 = r#"{
+        "name": "B",
+        "type": "record",
+        "fields": [
+            {"name": "field_one", "type": "A"}
+        ]
+    }"#;
+
+// if the schemas are not valid, this function will return an error
+let schemas = Schema::parse_list(&[raw_schema_1, raw_schema_2]).unwrap();
+
+// schemas can be printed for debugging
+println!("{:?}", schemas);
+```
+*N.B.* It is important to note that the composition of schema definitions requires schemas with names.
+For this reason, only schemas of type Record, Enum, and Fixed should be input into this function.
+
 The library provides also a programmatic interface to define schemas without encoding them in
 JSON (for advanced use), but we highly recommend the JSON interface. Please read the API
 reference in case you are interested.

src/error.rs

@@ -18,6 +18,9 @@ pub enum Error {
     #[error("Not a string value, required for uuid: {0:?}")]
     GetUuidFromStringValue(ValueKind),
 
+    #[error("Two schemas with the same fullname were given: {0:?}")]
+    NameCollision(String),
+
     #[error("Not a fixed or bytes type, required for decimal schema, got: {0:?}")]
     ResolveDecimalSchema(SchemaKind),
 

src/lib.rs

@@ -79,6 +79,38 @@
 //! println!("{:?}", schema);
 //! ```
 //!
+//! Additionally, a list of of definitions (which may depend on each other) can be given and all of
+//! them will be parsed into the corresponding schemas.
+//!
+//! ```
+//! use avro_rs::Schema;
+//!
+//! let raw_schema_1 = r#"{
+//!         "name": "A",
+//!         "type": "record",
+//!         "fields": [
+//!             {"name": "field_one", "type": "float"}
+//!         ]
+//!     }"#;
+//!
+//! // This definition depends on the definition of A above
+//! let raw_schema_2 = r#"{
+//!         "name": "B",
+//!         "type": "record",
+//!         "fields": [
+//!             {"name": "field_one", "type": "A"}
+//!         ]
+//!     }"#;
+//!
+//! // if the schemas are not valid, this function will return an error
+//! let schemas = Schema::parse_list(&[raw_schema_1, raw_schema_2]).unwrap();
+//!
+//! // schemas can be printed for debugging
+//! println!("{:?}", schemas);
+//! ```
+//! *N.B.* It is important to note that the composition of schema definitions requires schemas with names.
+//! For this reason, only schemas of type Record, Enum, and Fixed should be input into this function.
+//!
 //! The library provides also a programmatic interface to define schemas without encoding them in
 //! JSON (for advanced use), but we highly recommend the JSON interface. Please read the API
 //! reference in case you are interested.