appender: add fallback to file creation date

When using the linux-musl target for rust, the file creation time
cannot be retrieved, as the current version does not support it yet (
This will be fixed with [0]). In the meantime, we parse the datetime
from the filename and use that as a fallback.

Fixes: tokio-rs#2999

[0]: rust-lang/rust#125692

Author: kaffarell

tracing-appender/src/rolling.rs

@@ -34,7 +34,7 @@ use std::{
     path::{Path, PathBuf},
     sync::atomic::{AtomicUsize, Ordering},
 };
-use time::{format_description, Date, Duration, OffsetDateTime, Time};
+use time::{format_description, Date, Duration, OffsetDateTime, PrimitiveDateTime, Time};
 
 mod builder;
 pub use builder::{Builder, InitError};
@@ -602,7 +602,28 @@ impl Inner {
                     return None;
                 }
 
-                let created = metadata.created().ok()?;
+                let created = metadata.created().ok().or_else(|| {
+                    let datetime = if let (Some(prefix), Some(suffix)) =
+                        (&self.log_filename_prefix, &self.log_filename_suffix)
+                    {
+                        let date = filename
+                            .split(prefix)
+                            .last()?
+                            .split(suffix)
+                            .next()?
+                            .strip_prefix('.')?
+                            .strip_suffix('.')?;
+
+                        PrimitiveDateTime::parse(date, &self.date_format)
+                            .ok()?
+                            .assume_utc()
+                    } else {
+                        PrimitiveDateTime::parse(filename, &self.date_format)
+                            .ok()?
+                            .assume_utc()
+                    };
+                    Some(datetime.into())
+                })?;
                 Some((entry, created))
             })
             .collect::<Vec<_>>()