tracing: Make formatting better and document

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 36 insertions, 12 deletions

diff --git a/src/bin/subplot.rs b/src/bin/subplot.rs
index 29ed25e..f4eb678 100644
--- a/src/bin/subplot.rs
+++ b/src/bin/subplot.rs
@@ -8,7 +8,7 @@ use structopt::StructOpt;
 use subplot::{
     generate_test_program, resource, template_spec, DataFile, Document, MarkupOpts, Style,
 };
-use tracing::{event, span, Level};
+use tracing::{event, span, Level, Subscriber};
 
 use std::convert::TryFrom;
 use std::ffi::OsString;
@@ -439,6 +439,12 @@ fn real_main() {
     }
 }
 
+enum LogFormat {
+    Pretty,
+    OneLine,
+    Json,
+}
+
 fn main() {
     let filter = match tracing_subscriber::EnvFilter::try_from_env("SUBPLOT_LOG") {
         Ok(f) => f,
@@ -452,13 +458,27 @@ fn main() {
             }
         }
     };
-    match std::env::var("SUBPLOT_TRACE_LOG").ok().as_deref() {
+    let format = match std::env::var("SUBPLOT_LOG_FORMAT")
+        .map(|v| v.to_ascii_lowercase())
+        .as_deref()
+    {
+        Err(_) | Ok("oneline") | Ok("default") => LogFormat::OneLine,
+        Ok("pretty") => LogFormat::Pretty,
+        Ok("json") => LogFormat::Json,
+        Ok(v) => {
+            eprintln!("Unknown log format: {:?}", v);
+            process::exit(1);
+        }
+    };
+    let subscriber = match std::env::var("SUBPLOT_LOG_FILE").ok().as_deref() {
         None | Some("") | Some("-") => {
-            let subscriber = tracing_subscriber::fmt()
-                .with_env_filter(filter)
-                .pretty()
-                .finish();
-            tracing::subscriber::with_default(subscriber, real_main);
+            let subscriber = tracing_subscriber::fmt().with_env_filter(filter);
+            let subscriber: Box<dyn Subscriber + Send + Sync + 'static> = match format {
+                LogFormat::OneLine => Box::new(subscriber.finish()),
+                LogFormat::Pretty => Box::new(subscriber.pretty().finish()),
+                LogFormat::Json => Box::new(subscriber.json().with_ansi(false).finish()),
+            };
+            subscriber
         }
         Some(fname) => {
             let curdir = std::path::Component::CurDir;
@@ -472,10 +492,14 @@ fn main() {
             let subscriber = tracing_subscriber::fmt()
                 .with_writer(non_blocking)
                 .with_env_filter(filter)
-                .pretty()
-                .with_ansi(false)
-                .finish();
-            tracing::subscriber::with_default(subscriber, real_main);
+                .with_ansi(false);
+            let subscriber: Box<dyn Subscriber + Send + Sync + 'static> = match format {
+                LogFormat::OneLine => Box::new(subscriber.finish()),
+                LogFormat::Pretty => Box::new(subscriber.pretty().finish()),
+                LogFormat::Json => Box::new(subscriber.json().finish()),
+            };
+            subscriber
         }
-    }
+    };
+    tracing::subscriber::with_default(subscriber, real_main);
 }