fix preview of linux pseudo-files

For some reason, fs::metadata doesn't report a length of
zero anymore, so the old test didn't work.

3 files changed, 13 insertions, 3 deletions

diff --git a/src/errors.rs b/src/errors.rs
index 388b30d..7b2b01f 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -28,6 +28,7 @@ custom_error! {pub ProgramError
     ImageError {source: ImageError } = "{}",
     Lfs {details: String} = "Failed to fetch mounts: {}",
     ZeroLenFile = "File seems empty",
+    UnmappableFile = "File can't be mapped",
 }
 
 custom_error! {pub TreeBuildError
diff --git a/src/preview/preview.rs b/src/preview/preview.rs
index 63e4079..47a6812 100644
--- a/src/preview/preview.rs
+++ b/src/preview/preview.rs
@@ -82,7 +82,8 @@ impl Preview {
 
     }
     /// build a text preview (maybe with syntaxic coloring) if possible,
-    /// a hex (binary) view if content isnt't UTF8, or a IOError when
+    /// a hex (binary) view if content isnt't UTF8, a ZeroLen file if there's
+    /// no length (it's probably a linux pseudofile) or a IOError when
     /// there's a IO problem
     pub fn unfiltered_text(
         path: &Path,
@@ -90,8 +91,8 @@ impl Preview {
     ) -> Self {
         match SyntacticView::new(path, InputPattern::none(), &mut Dam::unlimited(), con) {
             Ok(Some(sv)) => Self::Syntactic(sv),
-            Err(ProgramError::ZeroLenFile) => {
-                debug!("zero len file - check if system file");
+            Err(ProgramError::ZeroLenFile | ProgramError::UnmappableFile) => {
+                debug!("zero len or unmappable file - check if system file");
                 Self::ZeroLen(ZeroLenFileView::new(path.to_path_buf()))
             }
             // not previewable as UTF8 text
diff --git a/src/syntactic/syntactic_view.rs b/src/syntactic/syntactic_view.rs
index d23d88e..b632171 100644
--- a/src/syntactic/syntactic_view.rs
+++ b/src/syntactic/syntactic_view.rs
@@ -104,6 +104,14 @@ impl SyntacticView {
         con: &AppContext,
     ) -> Result<bool, ProgramError> {
         let f = File::open(&self.path)?;
+        {
+            // if we detect the file isn't mappable, we'll
+            // let the ZeroLenFilePreview try to read it
+            let mmap = unsafe { Mmap::map(&f) };
+            if mmap.is_err() {
+                return Err(ProgramError::UnmappableFile);
+            }
+        }
         let md = f.metadata()?;
         if md.len() == 0 {
             return Err(ProgramError::ZeroLenFile);