Properly indent multiline messages

examples/basic.rs

@@ -2,6 +2,12 @@
 use tracing_subscriber::{layer::SubscriberExt, registry::Registry};
 use tracing_tree::HierarchicalLayer;
 
+#[derive(Debug)]
+struct PrettyPrintMe {
+    value_a: u32,
+    value_b: String,
+}
+
 fn main() {
     let layer = HierarchicalLayer::default()
         .with_writer(std::io::stdout)
@@ -50,6 +56,18 @@
         error!("hello");
     });
     drop(peer3);
+    let val = format!(
+        "{:#?}",
+        PrettyPrintMe {
+            value_a: 42,
+            value_b: "hello".into(),
+        }
+    );
+    let peer3 = span!(Level::TRACE, "", val = %val);
+    peer3.in_scope(|| {
+        error!("hello");
+    });
+    drop(peer3);
     let peer1 = span!(Level::TRACE, "conn", peer_addr = "82.9.9.9", port = 42381);
     peer1.in_scope(|| {
         warn!(algo = "xor", "weak encryption requested");
@@ -72,12 +90,12 @@
 }
 
 #[instrument]
 fn call_a(name: &str) {
     info!(name, "got a name");
     call_b(name)
 }
 
 #[instrument]
 fn call_b(name: &str) {
     info!(name, "got a name");
 }

examples/basic.stdout

@@ -20,6 +20,17 @@
 1:main   ┌┘basic::foomp 42 <- format string, normal_var=43
 1:main  ┌┘basic::server host="localhost", port=8080
 1:main  └┐basic::server host="localhost", port=8080
+1:main   └┐basic:: val=PrettyPrintMe {
+1:main    │      value_a: 42,
+1:main    │      value_b: "hello",
+1:main    │  }
+1:main    ├─ ERROR basic hello
+1:main   ┌┘basic:: val=PrettyPrintMe {
+1:main   │      value_a: 42,
+1:main   │      value_b: "hello",
+1:main   │  }
+1:main  ┌┘basic::server host="localhost", port=8080
+1:main  └┐basic::server host="localhost", port=8080
 1:main   └┐basic::conn peer_addr="82.9.9.9", port=42381
 1:main    ├─ WARN basic weak encryption requested, algo="xor"
 1:main    ├─ DEBUG basic response sent, length=8

examples/no-indent.rs

@@ -2,6 +2,12 @@ use tracing::{debug, error, info, instrument, span, warn, Level};
 use tracing_subscriber::{layer::SubscriberExt, registry::Registry};
 use tracing_tree::HierarchicalLayer;
 
+#[derive(Debug)]
+struct PrettyPrintMe {
+    value_a: u32,
+    value_b: String,
+}
+
 fn main() {
     let layer = HierarchicalLayer::default()
         .with_writer(std::io::stdout)
@@ -47,6 +53,18 @@ fn main() {
         error!("hello");
     });
     drop(peer3);
+    let val = format!(
+        "{:#?}",
+        PrettyPrintMe {
+            value_a: 42,
+            value_b: "hello".into(),
+        }
+    );
+    let peer3 = span!(Level::TRACE, "", val = %val);
+    peer3.in_scope(|| {
+        error!("hello");
+    });
+    drop(peer3);
     let peer1 = span!(Level::TRACE, "conn", peer_addr = "82.9.9.9", port = 42381);
     peer1.in_scope(|| {
         warn!(algo = "xor", "weak encryption requested");

examples/no-indent.stdout

@@ -9,6 +9,11 @@
 1:main      DEBUG no_indent connected
 1:main     no_indent::foomp 42 <- format string, normal_var=43
 1:main      ERROR no_indent hello
+1:main     no_indent:: val=PrettyPrintMe {
+1:main           value_a: 42,
+1:main           value_b: "hello",
+1:main       }
+1:main      ERROR no_indent hello
 1:main     no_indent::conn peer_addr="82.9.9.9", port=42381
 1:main      WARN no_indent weak encryption requested, algo="xor"
 1:main      DEBUG no_indent response sent, length=8

src/format.rs

@@ -253,7 +253,7 @@
         // Render something when wraparound occurs so the user is aware of it
         if config.indent_lines {
             match style {
                 SpanMode::PreOpen { .. } | SpanMode::Open { .. } => {
                     if indent > 0 && (indent + 1) % config.wraparound == 0 {
                         self.current_buf.push_str(&prefix);
                         for _ in 0..(indent % config.wraparound * config.indent_amount) {
@@ -347,7 +347,7 @@
                     SpanMode::Open { .. } => buf.push_str(LINE_OPEN),
                     SpanMode::Retrace { .. } => buf.push_str(LINE_OPEN),
                     SpanMode::Close { .. } => buf.push_str(LINE_CLOSE),
                     SpanMode::PreOpen { .. } | SpanMode::PostClose => {}
                     SpanMode::Event => {}
                 }
             }
@@ -448,12 +448,14 @@
 
     // add the rest of the indentation, since we don't want to draw horizontal lines
     // for subsequent lines
-    for i in 0..indent_amount {
-        if i % indent_amount == 0 {
-            s.push_str(LINE_VERT);
-        } else {
-            s.push(' ');
-        }
+    match style {
+        SpanMode::Open { .. } | SpanMode::Retrace { .. } => s.push_str("  "),
+        SpanMode::Close { .. } => s.push(' '),
+        _ => {}
+    }
+    s.push_str(LINE_VERT);
+    for _ in 1..=indent_amount {
+        s.push(' ');
     }
 
     // add all of the actual content, with each line preceded by the indent string
@@ -489,11 +491,16 @@
     if indent_lines {
         indent_block_with_lines(&lines, buf, indent, indent_amount, prefix, style);
     } else {
-        let indent_str = String::from(" ").repeat(indent_spaces);
+        let mut indent_str = " ".repeat(indent_spaces);
+        let mut first_line = true;
         for line in lines {
             buf.push_str(prefix);
             buf.push(' ');
             buf.push_str(&indent_str);
+            if first_line {
+                first_line = false;
+                indent_str.push_str("  ");
+            }
             buf.push_str(line);
             buf.push('\n');
         }