Use anyhow for error handling

This patch changes our error handling approach from the ground up:
instead of having a globally used Error enum that contains variants for
all possible errors, we now use anyhow's Error type. This approach is
more dynamic (and not statically typed), but it allows for more fine
grained error messages and overall more user-friendly error reporting.
Overall it also is a net simplification. While we have one dynamic cast
now, in order to be able to handle erroneous password/PIN entries
correctly, that is considered a reasonable compromise.

3 files changed, 12 insertions, 29 deletions

diff --git a/src/tests/otp.rs b/src/tests/otp.rs
index 7361688..65c1cb5 100644
--- a/src/tests/otp.rs
+++ b/src/tests/otp.rs
@@ -28,7 +28,7 @@ fn set_invalid_slot_raw(model: nitrokey::Model) {
 
   assert_ne!(rc, 0);
   assert_eq!(out, b"");
-  assert_eq!(&err[..24], b"Could not write OTP slot");
+  assert_eq!(&err[..24], b"Failed to write OTP slot");
 }
 
 #[test_device]
@@ -37,12 +37,8 @@ fn set_invalid_slot(model: nitrokey::Model) {
     .handle(&["otp", "set", "100", "name", "1234", "-f", "hex"])
     .unwrap_err()
     .to_string();
-  let expected = format!(
-    "Could not write OTP slot: {}",
-    nitrokey::Error::LibraryError(nitrokey::LibraryError::InvalidSlot)
-  );
 
-  assert_eq!(err, expected);
+  assert_eq!(err, "Failed to write OTP slot");
 }
 
 #[test_device]
@@ -122,10 +118,6 @@ fn clear(model: nitrokey::Model) -> crate::Result<()> {
   let res = ncli.handle(&["otp", "get", "3"]);
 
   let err = res.unwrap_err().to_string();
-  let expected = format!(
-    "Could not generate OTP: {}",
-    nitrokey::Error::CommandError(nitrokey::CommandError::SlotNotProgrammed)
-  );
-  assert_eq!(err, expected);
+  assert_eq!(err, "Failed to generate OTP");
   Ok(())
 }
diff --git a/src/tests/pws.rs b/src/tests/pws.rs
index 7f8107e..910ef92 100644
--- a/src/tests/pws.rs
+++ b/src/tests/pws.rs
@@ -25,12 +25,8 @@ fn set_invalid_slot(model: nitrokey::Model) {
     .handle(&["pws", "set", "100", "name", "login", "1234"])
     .unwrap_err()
     .to_string();
-  let expected = format!(
-    "Could not write PWS slot: {}",
-    nitrokey::Error::LibraryError(nitrokey::LibraryError::InvalidSlot)
-  );
 
-  assert_eq!(err, expected);
+  assert_eq!(err, "Failed to write PWS slot");
 }
 
 #[test_device]
@@ -97,11 +93,7 @@ fn set_reset_get(model: nitrokey::Model) -> crate::Result<()> {
 
   let res = ncli.handle(&["pws", "get", "2"]);
   let err = res.unwrap_err().to_string();
-  let expected = format!(
-    "Could not access PWS slot: {}",
-    nitrokey::Error::CommandError(nitrokey::CommandError::SlotNotProgrammed)
-  );
-  assert_eq!(err, expected);
+  assert_eq!(err, "Failed to access PWS slot");
   Ok(())
 }
 
@@ -113,10 +105,6 @@ fn clear(model: nitrokey::Model) -> crate::Result<()> {
   let res = ncli.handle(&["pws", "get", "10"]);
 
   let err = res.unwrap_err().to_string();
-  let expected = format!(
-    "Could not access PWS slot: {}",
-    nitrokey::Error::CommandError(nitrokey::CommandError::SlotNotProgrammed)
-  );
-  assert_eq!(err, expected);
+  assert_eq!(err, "Failed to access PWS slot");
   Ok(())
 }
diff --git a/src/tests/status.rs b/src/tests/status.rs
index e80fadc..c617a9e 100644
--- a/src/tests/status.rs
+++ b/src/tests/status.rs
@@ -19,15 +19,18 @@
 
 use super::*;
 
-// This test acts as verification that conversion of Error::Error
-// variants into the proper exit code works properly.
 #[test_device]
 fn not_found_raw() {
   let (rc, out, err) = Nitrocli::new().run(&["status"]);
 
   assert_ne!(rc, 0);
   assert_eq!(out, b"");
-  assert_eq!(err, b"Nitrokey device not found\n");
+  let expected = r#"Nitrokey device not found
+
+Caused by:
+    Communication error: Could not connect to a Nitrokey device
+"#;
+  assert_eq!(err, expected.as_bytes());
 }
 
 #[test_device]