From 97d1a81b7c1e05b3a8d0f91af52e35377bb65296 Mon Sep 17 00:00:00 2001
From: teor <teor@riseup.net>
Date: Tue, 1 Dec 2020 11:08:55 +1000
Subject: [PATCH] Automatically disable colors when tracing to a file

---
 Cargo.lock                                 | 1 +
 zebrad/Cargo.toml                          | 1 +
 zebrad/src/components/tracing/component.rs | 5 ++++-
 zebrad/src/config.rs                       | 6 +++++-
 4 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 97397db9..f8ad6ff6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3555,6 +3555,7 @@ name = "zebrad"
 version = "3.0.0-alpha.0"
 dependencies = [
  "abscissa_core",
+ "atty",
  "chrono",
  "color-eyre",
  "dirs",
diff --git a/zebrad/Cargo.toml b/zebrad/Cargo.toml
index eb022121..04cb210f 100644
--- a/zebrad/Cargo.toml
+++ b/zebrad/Cargo.toml
@@ -39,6 +39,7 @@ metrics-exporter-prometheus = "0.1.0-alpha.10"
 
 dirs = "3.0.1"
 inferno = { version = "0.10.2", default-features = false }
+atty = "0.2.14"
 
 [build-dependencies]
 vergen = "3.1.0"
diff --git a/zebrad/src/components/tracing/component.rs b/zebrad/src/components/tracing/component.rs
index 491dba73..e6f94448 100644
--- a/zebrad/src/components/tracing/component.rs
+++ b/zebrad/src/components/tracing/component.rs
@@ -21,9 +21,12 @@ impl Tracing {
         let filter = config.filter.unwrap_or_else(|| "".to_string());
         let flame_root = &config.flamegraph;
 
+        // Only use color if tracing output is being sent to a terminal
+        let use_color = config.use_color && atty::is(atty::Stream::Stdout);
+
         // Construct a tracing subscriber with the supplied filter and enable reloading.
         let builder = FmtSubscriber::builder()
-            .with_ansi(config.use_color)
+            .with_ansi(use_color)
             .with_env_filter(filter)
             .with_filter_reloading();
         let filter_handle = builder.reload_handle();
diff --git a/zebrad/src/config.rs b/zebrad/src/config.rs
index a0d2b517..d836be15 100644
--- a/zebrad/src/config.rs
+++ b/zebrad/src/config.rs
@@ -45,7 +45,11 @@ pub struct ZebradConfig {
 pub struct TracingSection {
     /// Whether to use colored terminal output, if available.
     ///
-    /// Defaults to `true`.
+    /// Colored terminal output is automatically disabled if an output stream
+    /// is connected to a file. (Or another non-terminal device.)
+    ///
+    /// Defaults to `true`, which automatically enables colored output to
+    /// terminals.
     pub use_color: bool,
 
     /// The filter used for tracing events.