Uclicious

• What is Uclicious
• Usage
  • Raw API
  • Derive-driven
    • Validators
    • Type Mapping
  • Supported attributes (#[ucl(..)])
    • Structure level
    • Field level
  • Additional notes
• Contributing
  • Particular Contributions of Interest
• Goals
  • Not Goals
• Special thanks
• LICENSE

What is Uclicious

Uclicious is a flexible reduced boilerplate configuration framework.

Uclicious is built on top of libucl. If you ever wrote an nginx configurtion and though "Damn, I wish all configuration files were like this" this is the library for you. Internal parser supports both: nginx-like and json-like formats. JSON parser is a little bit more permissive than - every json file is a valid UCL file, but not other way around. It is much more complex than json or TOML, so I recommend reading documentaiton about it. Author of UCL did a great job documenting it. This library provides both: derive-driven and raw-api driven usage patterns.

Usage

Raw API

Raw API involves interacting with libucl parser via safe api:

use uclicious::*;
let mut parser = Parser::default();
let input = r#"
test_string = "no scope"
a_float = 3.14
an_integer = 69420
is_it_good = yes
buffer_size = 1KB
interval = 1s
"#;
parser.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
let result = parser.get_object().unwrap();

let lookup_result = result.lookup("test_string").unwrap().as_string().unwrap();
assert_eq!(lookup_result.as_str(), "no scope");

let lookup_result = result.lookup("a_float").unwrap().as_f64().unwrap();
assert_eq!(lookup_result, 3.14f64);

let lookup_result = result.lookup("an_integer").unwrap().as_i64().unwrap();
assert_eq!(lookup_result, 69420i64);

let lookup_result = result.lookup("is_it_good").unwrap().as_bool().unwrap();
assert_eq!(lookup_result, true);

let lookup_result = result.lookup("buffer_size").unwrap().as_i64().unwrap();
assert_eq!(lookup_result, 1024);
let lookup_result = result.lookup("interval").unwrap().as_time().unwrap();
assert_eq!(lookup_result, 1.0f64);

In order to get around rust rules library implemets its own trait FromObject for some basic types:

use uclicious::*;
let mut parser = Parser::default();
let input = r#"
test_string = "no scope"
a_float = 3.14
an_integer = 69420
is_it_good = yes
buffer_size = 1KB
"#;
parser.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
let result = parser.get_object().unwrap();

let lookup_result = result.lookup("is_it_good").unwrap();
let maybe: Option<bool> = FromObject::try_from(lookup_result).unwrap();
assert_eq!(Some(true), maybe);

Derive-driven

On top of "raw" interface to libUCL, Uclicious provides an easy way to derive constructor for strucs:

use uclicious::*;
use std::path::PathBuf;
use std::net::SocketAddr;
use std::collections::HashMap;
use std::time::Duration;

#[derive(Debug,Uclicious)]
#[ucl(var(name = "test", value = "works"))]
struct Connection {
   #[ucl(default)]
   enabled: bool,
   host: String,
   #[ucl(default = "420")]
   port: i64,
   buffer: u64,
   #[ucl(path = "type")]
   kind: String,
   locations: Vec<PathBuf>,
   addr: SocketAddr,
   extra: Extra,
   #[ucl(path = "subsection.host")]
   hosts: Vec<String>,
   #[ucl(default)]
   option: Option<String>,
   gates: HashMap<String, bool>,
   interval: Duration,
}

#[derive(Debug,Uclicious)]
#[ucl(skip_builder)]
struct Extra {
   enabled: bool
}
let mut builder = Connection::builder().unwrap();

let input = r#"
    enabled = yes
    host = "some.fake.url"
    buffer = 1mb
    type = $test
    locations = "/etc/"
    addr = "127.0.0.1:80"
    extra = {
       enabled = on
   }
    subsection {
       host = [host1, host2]
   }
   interval = 10ms
   gates {
        feature_1 = on
        feature_2 = off
        feature_3 = on
   }"#;

builder.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
let connection: Connection = builder.build().unwrap();

If you choose to derive builder then ::builder() method will be added to target struct.

Validators

Library supports running optional validators on values before building the resulting struct:

use uclicious::*;
mod validators {
   use uclicious::ObjectError;
    pub fn is_positive(lookup_path: &str, value: &i64) -> Result<(), ObjectError> {
        if *value > 0 {
            Ok(())
        } else {
            Err(ObjectError::other(format!("{} is not a positive number", lookup_path)))
        }
    }
}
#[derive(Debug,Uclicious)]
struct Validated {
   #[ucl(default, validate="validators::is_positive")]
    number: i64
}
let mut builder = Validated::builder().unwrap();

let input = "number = -1";
builder.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
assert!(builder.build().is_err())

Type Mapping

If your target structure has types that don't implement FromObject you can use From or TryFrom via intermediate that does:

use uclicious::*;
use std::convert::{From,TryFrom};

#[derive(Debug, Eq, PartialEq)]
enum Mode {
    On,
    Off,
}

impl TryFrom<String> for Mode {
    type Error = ObjectError;
    fn try_from(src: String) -> Result {
        match src.to_lowercase().as_str() {
            "on" => Ok(Mode::On),
            "off" => Ok(Mode::Off),
            _   => Err(ObjectError::other(format!("{} is not supported value", src)))
        }
    }
}

#[derive(Debug, Eq, PartialEq)]
struct WrappedInt(i64);

impl From<i64> for WrappedInt {
    fn from(src: i64) -> WrappedInt {
        WrappedInt(src)
    }
}

#[derive(Debug,Uclicious, Eq, PartialEq)]
struct Mapped {
   #[ucl(from="i64")]
    number: WrappedInt,
   #[ucl(try_from="String")]
    mode: Mode
}
let mut builder = Mapped::builder().unwrap();

let input = r#"
    number = -1,
    mode = "on"
"#;
builder.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
let actual = builder.build().unwrap();
let expected = Mapped {
number: WrappedInt(-1),
mode: Mode::On
};
assert_eq!(expected, actual);

Additionally you can provide mapping to your type from ObjectRef:

use uclicious::*;

#[derive(Debug, Eq, PartialEq)]
pub enum Mode {
    On,
    Off,
}

pub fn map_bool(src: ObjectRef) -> Result {
    let bool: bool = src.try_into()?;
    if bool {
        Ok(Mode::On)
    } else {
        Ok(Mode::Off)
    }
}
#[derive(Debug,Uclicious, Eq, PartialEq)]
struct Mapped {
   #[ucl(map="map_bool")]
    mode: Mode
}
let mut builder = Mapped::builder().unwrap();

let input = r#"
    mode = on
"#;
builder.add_chunk_full(input, Priority::default(), DEFAULT_DUPLICATE_STRATEGY).unwrap();
let actual = builder.build().unwrap();
let expected = Mapped {
    mode: Mode::On
};

Supported attributes (#[ucl(..)])

Structure level

• skip_builder
  • if set, then builder and builder methods won't be generated.
• parser(..)
  • Optional attribute to configure inner parser.
  • Has following nested attributes:
    • flags
      • a path to function that returns flags.
    • filevars(..)
      • call set_filevars on a parser.
      • Has following nested attributes:
        • path
          • a string representation of filepath.
        • expand
          • (optional) if set, then variables would be expanded to absolute.
• pre_source_hook(...)
  • Optional attribute to run a function before sources are added
  • Can be used to register vars handler
  • Must take &mut Parser as argument and return Result<(), Into>
• var(..)
  • Optional attribute to register string variables with the parser.
  • Has following nested attributes:
    • name
      • A name of the variable without $ part.
    • value
      • A string values for the variable.
      • Onlt string variables are supported by libUCL.
• include(..)
  • Used to add files into the parser.
  • If file doesn't exist or failed to parse, then error will be returned in a constructor.
  • Must specify exactly one of following sources: path, chunk or chunk_static
  • Has following nested attirbutes:
    • (semi-optional) path = string
      • File path. Can be absolute or relative to CWD.
    • (semi-optional) chunk = string
      • A string that will be added to parser as a chunk.
    • (semi-optional) chunk_static = string
      • A path to a file that will be included into binary with include_str!()
    • (optional) priority = u32
      • 0-15 priority for the source. Consult the libUCL documentation for more information.
    • (optional) strategy = uclicious::DuplicateStrategy
      • Strategy to use for duplicate keys. Consult the libUCL documentation for more information.

Field level

All field level options are optional.

• default
  • Use Default::default if key not found in object.
• default = expression
  • Use this expression as value if key not found.
  • Could be a value or a function call.
• path = string
  • By default field name is used as path.
  • If set that would be used as a key.
  • dot notation for key is supported.
• validate = path::to_method
  • Fn(key: &str, value: &T) -> Result<(), E>
  • Error needs to be convertable into ObjectError
• from = Type
  • Try to convert ObjectRef to Type and then use std::convert::From to convert into target type
• try_from = Type
  • Try to convert ObjectRef to Type and then use std::convert::TryFrom to convert into target type
  • Error will be converted into ObjectError::Other
• map = path::to_method
  • Fn(src: ObjectRef) -> Result
  • A way to map foreign objects that can't implement From or TryFrom or when error is not convertable into ObjectError

Additional notes

• If target type is an array, but key is a single value — an implicit list is created.
• Automatic derive on enums is not supported, but you can implement it yourself.
• I have a few more features I want to implement before publishing this crate:
  • Ability to add variables.
  • Ability to add macross handlers.
  • (maybe) configure parser that us used for derived builder with atrributes.
  • (done) add sources to parser with attributes.

Contributing

PRs, feature requests, bug reports are welcome. I won't be adding CoC — be civilized.

Particular Contributions of Interest

• Optimize derive code.
• Improve documentation — I often write late and night and some it might look like a word soup.
• Better tests
• Glob support in derive parser section
• Variable handler

Goals

• Provider safe and convient configuration library
• Automatic derive, so you don't have to think about parser object

Not Goals

• Providing UCL Object generation tools is not a goal for this project
• 1:1 interface to libUCL
• sugar inside raw module

Special thanks

• draft6 and hauleth
  • libucl-rs was a good starting point
  • Type wrappers pretty much copied from there
• colin-kiegel
  • Rust-derive-builder was used as a starting point for uclicious-derive
  • Very well documented proc_macro crate, do recommend

LICENSE

BSD-2-Clause.