67 lines
1.7 KiB
Rust
67 lines
1.7 KiB
Rust
//! Demonstrates usage of `Error::caused` method. This method enables chaining errors
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//! like `ResultExt::chain_err` but doesn't require the presence of a `Result` wrapper.
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#[macro_use]
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extern crate error_chain;
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use std::fs::File;
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mod errors {
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use super::LaunchStage;
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use std::io;
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error_chain! {
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foreign_links {
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Io(io::Error) #[doc = "Error during IO"];
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}
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errors {
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Launch(phase: LaunchStage) {
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description("An error occurred during startup")
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display("Startup aborted: {:?} did not complete successfully", phase)
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}
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ConfigLoad(path: String) {
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description("Config file not found")
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display("Unable to read file `{}`", path)
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}
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}
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}
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impl From<LaunchStage> for ErrorKind {
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fn from(v: LaunchStage) -> Self {
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ErrorKind::Launch(v)
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}
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}
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}
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pub use errors::*;
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub enum LaunchStage {
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ConfigLoad,
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ConfigParse,
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ConfigResolve,
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}
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/// Read the service config from the file specified.
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fn load_config(rel_path: &str) -> Result<()> {
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File::open(rel_path)
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.map(|_| ())
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.chain_err(|| ErrorKind::ConfigLoad(rel_path.to_string()))
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}
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/// Launch the service.
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fn launch(rel_path: &str) -> Result<()> {
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load_config(rel_path).map_err(|e| match e {
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e @ Error(ErrorKind::ConfigLoad(_), _) => e.chain_err(|| LaunchStage::ConfigLoad),
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e => e.chain_err(|| "Unknown failure"),
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})
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}
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fn main() {
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let chain = launch("does_not_exist.json").unwrap_err();
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for err in chain.iter() {
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println!("{}", err);
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}
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}
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