Struct spirit_cfg_helpers::CfgDump

pub struct CfgDump { /* private fields */ }

A command line fragment add --dump-config to allow showing loaded configuration.

When this is added into the command line options structure, the --dump-config and --dump-config-as options are added.

These dump the current configuration and exit.

In case the configuration is collected over multiple configuration files, directories and possibly environment variables and command line overrides, it is not always clear what exact configuration is actually used. This allows the user to query the actual configuration the application would use.

The fragment can be either used manually with the dump method or automatically by registering its helper.

Requirements

For this to work, the configuration structure must implement Serialize. This is not mandated by Spirit itself. However, all the fragments provided by spirit crates implement it. For custom structures it is often sufficient to stick #[derive(Serialize)] onto them.

Examples

use serde_derive::{Deserialize, Serialize};
use spirit::Spirit;
use spirit_cfg_helpers::CfgDump;
use structopt::StructOpt;

#[derive(Default, Deserialize, Serialize)]
struct Cfg {
    option: Option<String>,
}

#[derive(Debug, StructOpt)]
struct Opts {
    #[structopt(flatten)]
    dump: CfgDump,
}

impl Opts {
    fn dump(&self) -> &CfgDump {
        &self.dump
    }
}

fn main() {
    Spirit::<Opts, Cfg>::new()
        .with(CfgDump::helper(Opts::dump))
        .run(|_| Ok(()));
}

Implementations

impl CfgDump

pub fn dump<C: Serialize>(&self, cfg: &C)

Dump configuration if it is asked for in the options.

If the parsed options specify to dump the configuration, this does so and exits. If the options don’t specify that, it does nothing.

This can be used manually. However, the common way is to register the helper within a Builder and let it do everything automatically.

pub fn helper<O, C, F>(extract: F) -> impl Helper<O, C>where
    F: FnOnce(&O) -> &Self + Send + 'static,
    O: Debug + StructOpt + Send + Sync + 'static,
    C: DeserializeOwned + Serialize + Send + Sync + 'static,

A helper that can be registered with Builder::with.

The parameter is an extractor, a function that takes the whole command line options structure and returns a reference to just the CfgDump instance in there.

Note that for configuration to be dumped, it needs to be parsed first.

Also, as this exits if the dumping is requested, it makes some sense to register it sooner than later. It registers itself as a config_validator and it is not needed to validate parts of the configuration only to throw it out on the exit.

Trait Implementations

impl Clone for CfgDump

fn clone(&self) -> CfgDump

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CfgDump

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for CfgDump

fn default() -> CfgDump

Returns the “default value” for a type.

impl StructOpt for CfgDump

fn clap<'a, 'b>() -> App<'a, 'b>

Returns the corresponding clap::App.

fn from_clap(matches: &ArgMatches<'_>) -> Self

Creates the struct from clap::ArgMatches. It cannot fail with a parameter generated by clap by construction.

fn from_args() -> Selfwhere
    Self: Sized,

Gets the struct from the command line arguments. Print the error message and quit the program in case of failure.

fn from_iter<I>(iter: I) -> Selfwhere
    Self: Sized,
    I: IntoIterator,
    <I as IntoIterator>::Item: Into<OsString> + Clone,

Gets the struct from any iterator such as a Vec of your making. Print the error message and quit the program in case of failure.

fn from_iter_safe<I>(iter: I) -> Result<Self, Error>where
    Self: Sized,
    I: IntoIterator,
    <I as IntoIterator>::Item: Into<OsString> + Clone,

Gets the struct from any iterator such as a Vec of your making.