Strip dependencies of bat-as-a-library

src/errors.rs

@@ -2,20 +2,20 @@ use error_chain::error_chain;
 
 error_chain! {
     foreign_links {
-        Clap(::clap::Error);
-        Io(::std::io::Error);
-        SyntectError(::syntect::LoadingError);
-        ParseIntError(::std::num::ParseIntError);
-        GlobParsingError(::globset::Error);
+        Clap(clap::Error);
+        Io(std::io::Error);
+        SyntectError(syntect::LoadingError);
+        ParseIntError(std::num::ParseIntError);
+        GlobParsingError(globset::Error);
     }
 }
 
 pub fn default_error_handler(error: &Error) {
     match error {
         Error(ErrorKind::Io(ref io_error), _)
-            if io_error.kind() == ::std::io::ErrorKind::BrokenPipe =>
+            if io_error.kind() == std::io::ErrorKind::BrokenPipe =>
         {
-            ::std::process::exit(0);
+            std::process::exit(0);
         }
         _ => {
             use ansi_term::Colour::Red;
@@ -23,3 +23,36 @@ pub fn default_error_handler(error: &Error) {
         }
     };
 }
+
+// Mock out a type for clap::Error if we aren't pulling in a dependency on clap.
+//
+// This can be removed after migrating away from error_chain to some modern
+// derive-based error library such as thiserror, in favor of:
+//
+//     #[derive(Error)]
+//     pub enum Error {
+//         #[cfg(feature = "application")]
+//         Clap(clap::Error),
+//         ...
+//     }
+//
+#[cfg(not(feature = "application"))]
+mod clap {
+    use std::fmt::{self, Debug, Display};
+
+    pub struct Error(());
+
+    impl Display for Error {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unreachable!()
+        }
+    }
+
+    impl Debug for Error {
+        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
+            unreachable!()
+        }
+    }
+
+    impl std::error::Error for Error {}
+}