open pl files instead of directories (#2014)

src/machine/streams.rs

@@ -27,6 +27,7 @@ use std::io::{Cursor, ErrorKind, Read, Seek, SeekFrom, Write};
 use std::mem;
 use std::net::{Shutdown, TcpStream};
 use std::ops::{Deref, DerefMut};
+use std::path::PathBuf;
 use std::ptr;
 
 #[cfg(feature = "tls")]
@@ -1837,7 +1838,10 @@ impl MachineState {
             }
         };
 
-        let file = match open_options.open(&*file_spec.as_str()) {
+        let mut path = PathBuf::from(&*file_spec.as_str());
+
+        loop {
+            let file = match open_options.open(&path) {
                 Ok(file) => file,
                 Err(err) => {
                     match err.kind() {
@@ -1869,10 +1873,20 @@ impl MachineState {
                 }
             };
 
-        Ok(if is_input_file {
+            if path.extension().is_none() {
+                if let Some(metadata) = file.metadata().ok() {
+                    if metadata.is_dir() {
+                        path.set_extension("pl");
+                        continue;
+                    }
+                }
+            }
+
+            return Ok(if is_input_file {
                 Stream::from_file_as_input(file_spec, file, &mut self.arena)
             } else {
                 Stream::from_file_as_output(file_spec, file, in_append_mode, &mut self.arena)
-        })
+            });
+        }
     }
 }