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};
@@ -657,7 +657,21 @@ impl Inner {
                     return None;
                 }
 
-                let created = metadata.created().ok()?;
+                let created = metadata.created().ok().or_else(|| {
+                    let mut datetime = filename;
+                    if let Some(prefix) = &self.log_filename_prefix {
+                        datetime = datetime.strip_prefix(prefix)?;
+                        datetime = datetime.strip_prefix('.')?;
+                    }
+                    if let Some(suffix) = &self.log_filename_suffix {
+                        datetime = datetime.strip_suffix(suffix)?;
+                        datetime = datetime.strip_suffix('.')?;
+                    }
+
+                    Some(PrimitiveDateTime::parse(datetime, &self.date_format)
+                        .ok()?
+                        .assume_utc().into())
+                })?;
                 Some((entry, created))
             })
             .collect::<Vec<_>>()