Fixed bug with `memfile` feature not setting stream length properly without `memfile-preallocate`

Fortune for collect's current commit: Future small blessing − 末小吉

src/main.rs

@@ -314,13 +314,17 @@ fn map_work() -> eyre::Result<()>
 	let read = io::copy(&mut stdin.lock(), &mut file)
 	    .with_section(|| format!("{:?}", file).header("Memory buffer file"))?;
 	
-	let read = if cfg!(any(feature="memfile-preallocate", debug_assertions)) {
+	let read =  {
 	    use io::*;
+	    use std::borrow::Cow;
+
+	    let (read, sp, sl) = if cfg!(any(feature="memfile-preallocate", debug_assertions)) {
 		let sp = file.stream_position();
 		let sl = memfile::stream_len(&file);
 		
 		if_trace!(trace!("Stream position after read: {:?}", sp));
 		if_trace!(trace!("Stream length after read: {:?}", sp));
+		
 		let read = match sp.as_ref() {
 		    Ok(&v) if v != read  => {
 			if_trace!(warn!("Reported read value not equal to memfile stream position: expected from `io::copy()`: {v}, got {read}"));
@@ -338,7 +342,6 @@ fn map_work() -> eyre::Result<()>
 
 		let truncate_stream = |bad: u64, good: u64| {
 		    use std::num::NonZeroU64;
-		use std::borrow::Cow;
 		    file.set_len(good)
 			.map(|_| good)
 			.with_section(|| match NonZeroU64::new(bad) {Some (b) => Cow::Owned(b.get().to_string()), None => Cow::Borrowed("<unknown>") }.header("Original (bad) length"))
@@ -368,16 +371,21 @@ fn map_work() -> eyre::Result<()>
 			read
 		    }
 		};
+		(read, Some(sp), Some(sl))
+	    } else {
+		(read, None, None)
+	    };
 
 	    file.seek(SeekFrom::Start(0))
 		.with_section(|| read.header("Actual read bytes"))
 		.wrap_err(eyre!("Failed to seek back to start of memory buffer file for output")
-			  .with_section(|| unwrap_int_string(sp).header("Memfile position"))
+			  .with_section(move || if let Some(sp) = sp { Cow::Owned(unwrap_int_string(sp)) }
+					else { Cow::Borrowed("<unknown>")  }.header("Memfile position"))
+			  .with_section(move || if let Some(sp) = sl { Cow::Owned(unwrap_int_string(sp)) }
+					else { Cow::Borrowed("<unknown>")  }.header("Memfile full length"))
 			  /*.with_section(|| file.stream_len().map(|x| x.to_string())
 			  .unwrap_or_else(|e| format!("<unknown: {e}>")).header("Memfile full length"))*/)?;
 	    
-	    read
-	} else {
 	    read
 	};