rsgen-avro  

A command line tool and library for generating serde-compatible Rust types from Avro schemas. The apache-avro crate, which is re-exported, provides a way to read and write Avro data with such types.

Command line usage

Download the latest release.

Available options rsgen-avro --help:

Generate Rust types from Avro schemas

Usage: rsgen-avro [OPTIONS] <GLOB_PATTERN> <OUTPUT_FILE>

Arguments:
  <GLOB_PATTERN>  Glob pattern to select Avro schema files
  <OUTPUT_FILE>   The file where Rust types will be written, '-' for stdout

Options:
      --fmt                      Run rustfmt on the resulting <output-file>
      --nullable                 Replace null fields with their default value when deserializing
      --precision <P>            Precision for f32/f64 default values that aren't round numbers [default: 3]
      --union-deser              Custom deserialization for apache-avro multi-valued union types
      --chrono-dates             Use chrono::NaiveDateTime for date/timestamps logical types
      --derive-builders          Derive builders for generated record structs
      --impl-schemas <METHOD>    Implement AvroSchema for generated record structs [default: none] [possible values: derive, copy-build-schema, none]
      --extra-derives <DERIVES>  Extract Derives for generated record structs, comma separated, e.g. `std::fmt::Display,std::string::ToString`
  -h, --help                     Print help (see more with '--help')
  -V, --version                  Print version

Library usage

As a library, the basic usage is:

use rsgen_avro::{Source, Generator};

let raw_schema = r#"
{
    "type": "record",
    "name": "test",
    "fields": [
        {"name": "a", "type": "long", "default": 42},
        {"name": "b", "type": "string"}
    ]
}
"#;

let source = Source::SchemaStr(&raw_schema);
let mut out = std::io::stdout();

let g = Generator::new().unwrap();
g.generate(&source, &mut out).unwrap();

This will generate the following output:

#[derive(Debug, PartialEq, Eq, Clone, serde::Deserialize, serde::Serialize)]
pub struct Test {
    #[serde(default = "default_test_a")]
    pub a: i64,
    pub b: String,
}

#[inline(always)]
fn default_test_a() -> i64 { 42 }

Various Schema sources can be used with Generator::generate(source, output) method:

pub enum Source<'a> {
    Schema(&'a rsgen_avro::Schema),    // Avro schema enum re-exported from `apache-avro`
    Schemas(&'a [rsgen_avro::Schema]), // A slice of Avro schema enums
    SchemaStr(&'a str),                // Schema as a json string
    GlobPattern(&'a str),              // Glob pattern to select schema files
}

Note also that the Generator can be customized with a builder:

let generator = rsgen_avro::Generator::builder()
    .precision(2)
    .build()
    .unwrap();

See GeneratorBuilder documentation for all available options.

Limitations

• Avro schema namespace fields are ignored, therefore record names within a schema (and across schemas) must not conflict (i.e. must be unique).
• Rust Option<T> are supported through Avro unions having "null" in their first position only (See #39)