configure logging through command-line args

Cargo.lock

@@ -2,6 +2,15 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "ansi_term"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
+dependencies = [
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "anyhow"
 version = "1.0.38"
@@ -31,6 +40,17 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi 0.3.9",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.0.1"
@@ -125,6 +145,21 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "clap"
+version = "2.33.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "37e58ac78573c40708d45522f0d80fa2f01cc4f9b4e2bf749807255454312002"
+dependencies = [
+ "ansi_term",
+ "atty",
+ "bitflags",
+ "strsim",
+ "textwrap",
+ "unicode-width",
+ "vec_map",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.9.1"
@@ -358,6 +393,15 @@ dependencies = [
  "wasi",
 ]
 
+[[package]]
+name = "heck"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "87cbf45460356b7deeb5e3415b5563308c0a9b057c85e12b06ad551f98d0a6ac"
+dependencies = [
+ "unicode-segmentation",
+]
+
 [[package]]
 name = "hermit-abi"
 version = "0.1.18"
@@ -737,6 +781,7 @@ dependencies = [
  "pin-project",
  "rustls-connector",
  "serde",
+ "structopt",
  "tokio",
  "tokio-rustls",
  "tokio-util",
@@ -814,6 +859,30 @@ version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ac74c624d6b2d21f425f752262f42188365d7b8ff1aff74c82e45136510a4857"
 
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check 0.9.2",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check 0.9.2",
+]
+
 [[package]]
 name = "proc-macro-hack"
 version = "0.5.19"
@@ -1110,6 +1179,36 @@ version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6e63cff320ae2c57904679ba7cb63280a3dc4613885beafb148ee7bf9aa9042d"
 
+[[package]]
+name = "strsim"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ea5119cdb4c55b55d432abb513a0429384878c15dde60cc77b1c99de1a95a6a"
+
+[[package]]
+name = "structopt"
+version = "0.3.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5277acd7ee46e63e5168a80734c9f6ee81b1367a7d8772a2d765df2a3705d28c"
+dependencies = [
+ "clap",
+ "lazy_static",
+ "structopt-derive",
+]
+
+[[package]]
+name = "structopt-derive"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ba9cdfda491b814720b6b06e0cac513d922fc407582032e8706e9f137976f90"
+dependencies = [
+ "heck",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.60"
@@ -1141,6 +1240,15 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "textwrap"
+version = "0.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
+dependencies = [
+ "unicode-width",
+]
+
 [[package]]
 name = "time"
 version = "0.1.44"
@@ -1219,6 +1327,18 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "unicode-segmentation"
+version = "1.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb0d2e7be6ae3a5fa87eed5fb451aff96f2573d2694942e40543ae0bbe19c796"
+
+[[package]]
+name = "unicode-width"
+version = "0.1.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9337591893a19b88d8d87f2cec1e73fad5cdfd10e5a6f349f498ad6ea2ffb1e3"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.1"
@@ -1237,6 +1357,12 @@ version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b00bca6106a5e23f3eee943593759b7fcddb00554332e856d990c893966879fb"
 
+[[package]]
+name = "vec_map"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
+
 [[package]]
 name = "version_check"
 version = "0.1.5"

Cargo.toml

@@ -29,3 +29,4 @@ xdg = "2.2.0"
 imap = { path = "imap" }
 toml = "0.5.8"
 serde = { version = "1.0.123", features = ["derive"] }
+structopt = "0.3.21"

src/main.rs

@@ -13,18 +13,29 @@ mod ui;
 
 use std::fs::File;
 use std::io::Read;
+use std::path::PathBuf;
 
 use anyhow::Result;
 use futures::future::TryFutureExt;
+use structopt::StructOpt;
 use tokio::sync::{mpsc, oneshot};
 
 use crate::config::Config;
 
 type ExitSender = oneshot::Sender<()>;
 
+#[derive(Debug, StructOpt)]
+struct Opt {
+    /// The path to the log file. By default, does not log.
+    #[structopt(long = "log-file")]
+    log_file: Option<PathBuf>,
+}
+
 #[tokio::main]
 async fn main() -> Result<()> {
-    setup_logger()?;
+    let opt = Opt::from_args();
+
+    setup_logger(&opt)?;
 
     let config: Config = {
         let mut config_file = File::open("config.toml")?;
@@ -48,8 +59,8 @@ fn report_err(err: anyhow::Error) {
     error!("error: {:?}", err);
 }
 
-fn setup_logger() -> Result<()> {
+fn setup_logger(opt: &Opt) -> Result<()> {
-    fern::Dispatch::new()
+    let mut fern = fern::Dispatch::new()
         .format(|out, message, record| {
             out.finish(format_args!(
                 "{}[{}][{}] {}",
@@ -59,8 +70,12 @@ fn setup_logger() -> Result<()> {
                 message
             ))
         })
-        .level(log::LevelFilter::Debug)
+        .level(log::LevelFilter::Debug);
-        .chain(fern::log_file("output.log")?)
+
-        .apply()?;
+    if let Some(path) = &opt.log_file {
+        fern = fern.chain(fern::log_file(path)?);
+    }
+
+    fern.apply()?;
     Ok(())
 }