fix: use indicatif-log-bridge to avoid breaking progress bar on log (#1747)

Tentative fix for #1746 using
[`indicatif-log-bridge`](https://github.com/djugei/indicatif-log-bridge).

Marking as "draft" PR since it adds some flickering to the progress bar.
I have to investigate this.

Fixes #1746.

Author: LucaCiucci

src/config/logging.rs

@@ -17,6 +17,8 @@ use log4rs::{
 use serde::{Deserialize, Serialize};
 use serde_with::{DisplayFromStr, serde_as};
 
+use crate::config::progress_options::multi_progress;
+
 /// Logging Config
 #[serde_as]
 #[derive(Default, Debug, Parser, Clone, Deserialize, Serialize, Merge)]
@@ -77,6 +79,7 @@ impl LoggingOptions {
             .target(Target::Stderr)
             .encoder(Box::new(PatternEncoder::new("{h([{l}])} {m}{n}")))
             .build();
+        let stdout = PbPauseAppender(stdout);
 
         let mut root_builder = Root::builder().appender("stdout");
         let mut config_builder = Config::builder().appender(
@@ -119,3 +122,22 @@ impl LoggingOptions {
         Ok(())
     }
 }
+
+/// A wrapper around [`ConsoleAppender`] that suspends the progress bar when writing logs.
+#[derive(Debug)]
+struct PbPauseAppender(ConsoleAppender);
+
+impl log4rs::append::Append for PbPauseAppender {
+    fn append(&self, record: &log::Record<'_>) -> Result<()> {
+        multi_progress().suspend(|| self.0.append(record))
+    }
+
+    fn flush(&self) {
+        // as of log4rs 1.4.0, <ConsoleAppender as Append>::flush does nothing,
+        // so we do not need to pause the progress bar here. In the future,
+        // if log4rs changes this behavior, we might need to add a suspend here.
+        // But that's not necessary right now, so we just call flush directly
+        // to avoid unnecessary suspends.
+        self.0.flush();
+    }
+}

src/config/progress_options.rs

@@ -3,11 +3,11 @@
 use std::{fmt::Write, time::Duration};
 
 use std::io::IsTerminal;
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, Mutex, OnceLock};
 use std::time::Instant;
 
 use bytesize::ByteSize;
-use indicatif::{HumanDuration, ProgressBar, ProgressState, ProgressStyle};
+use indicatif::{HumanDuration, MultiProgress, ProgressBar, ProgressState, ProgressStyle};
 
 use clap::Parser;
 use conflate::Merge;
@@ -19,6 +19,19 @@ use serde_with::{DisplayFromStr, serde_as};
 
 use rustic_core::{Progress, ProgressBars, ProgressType, RusticProgress};
 
+/// Returns the global `MultiProgress` instance used by all interactive progress bars.
+///
+/// Must be shared with `indicatif_log_bridge::LogWrapper` so that log output
+/// suspends progress bars before printing.
+pub fn multi_progress() -> &'static MultiProgress {
+    static MP: OnceLock<MultiProgress> = OnceLock::new();
+    MP.get_or_init(|| {
+        let mp = MultiProgress::new();
+        mp.set_move_cursor(true);
+        mp
+    })
+}
+
 mod constants {
     use std::time::Duration;
 
@@ -110,7 +123,7 @@ pub struct InteractiveProgress {
 impl InteractiveProgress {
     fn new(prefix: &str, kind: ProgressType, tick_interval: Duration) -> Self {
         let style = Self::initial_style(kind);
-        let bar = ProgressBar::new(0).with_style(style);
+        let bar = multi_progress().add(ProgressBar::new(0).with_style(style));
         bar.set_prefix(prefix.to_string());
         bar.enable_steady_tick(tick_interval);
         Self { bar, kind }