Add io cycle detection with clircle

src/controller.rs

@@ -13,6 +13,7 @@ use crate::output::OutputType;
 #[cfg(feature = "paging")]
 use crate::paging::PagingMode;
 use crate::printer::{InteractivePrinter, Printer, SimplePrinter};
+use std::convert::TryFrom;
 
 pub struct Controller<'a> {
     config: &'a Config<'a>,
@@ -66,6 +67,14 @@ impl<'b> Controller<'b> {
         }
 
         let attached_to_pager = output_type.is_pager();
+        let rw_cycle_detected = !attached_to_pager && {
+            let identifiers: Vec<_> = inputs
+                .iter()
+                .flat_map(clircle::Identifier::try_from)
+                .collect();
+            clircle::stdout_among_inputs(&identifiers)
+        };
+
         let writer = output_type.handle()?;
         let mut no_errors: bool = true;
 
@@ -78,6 +87,11 @@ impl<'b> Controller<'b> {
             }
         };
 
+        if rw_cycle_detected {
+            print_error(&"The output file is also an input!".into(), writer);
+            return Ok(false);
+        }
+
         for (index, input) in inputs.into_iter().enumerate() {
             match input.open(io::stdin().lock()) {
                 Err(error) => {

src/input.rs

@@ -1,6 +1,8 @@
+use std::convert::TryFrom;
 use std::ffi::{OsStr, OsString};
 use std::fs::File;
 use std::io::{self, BufRead, BufReader, Read};
+use std::path::Path;
 
 use content_inspector::{self, ContentType};
 
@@ -192,6 +194,18 @@ impl<'a> Input<'a> {
     }
 }
 
+impl TryFrom<&'_ Input<'_>> for clircle::Identifier {
+    type Error = ();
+
+    fn try_from(input: &Input) -> std::result::Result<clircle::Identifier, ()> {
+        match input.kind {
+            InputKind::OrdinaryFile(ref path) => Self::try_from(Path::new(path)).map_err(|_| ()),
+            InputKind::StdIn => Self::try_from(clircle::Stdio::Stdin).map_err(|_| ()),
+            InputKind::CustomReader(_) => Err(()),
+        }
+    }
+}
+
 pub(crate) struct InputReader<'a> {
     inner: Box<dyn BufRead + 'a>,
     pub(crate) first_line: Vec<u8>,