disk: Switch to ThisError

`ThisError` is now used as the standard across crosvm

Change-Id: I5e888c3af0bf98d6d00487ce48c92c929571bd6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2947799
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
Reviewed-by: Keiichi Watanabe <keiichiw@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
Commit-Queue: Dylan Reid <dgreid@chromium.org>

Cargo.lock

@@ -347,6 +347,7 @@ dependencies = [
  "protos",
  "remain",
  "tempfile",
+ "thiserror",
  "vm_memory",
 ]
 

disk/Cargo.toml

@@ -17,6 +17,7 @@ libc = "*"
 protobuf = { version = "2.3", optional = true }
 remain = "*"
 tempfile = "*"
+thiserror = "*"
 cros_async = { path = "../cros_async" }
 data_model = { path = "../data_model" }
 protos = { path = "../protos", optional = true }

disk/src/disk.rs

@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 use std::cmp::min;
-use std::fmt::{self, Debug, Display};
+use std::fmt::Debug;
 use std::fs::File;
 use std::io::{self, Read, Seek, SeekFrom, Write};
 use std::sync::Arc;
@@ -16,6 +16,7 @@ use base::{
 use cros_async::Executor;
 use libc::EINVAL;
 use remain::sorted;
+use thiserror::Error as ThisError;
 use vm_memory::GuestMemory;
 
 mod qcow;
@@ -30,25 +31,42 @@ mod android_sparse;
 use android_sparse::{AndroidSparse, SPARSE_HEADER_MAGIC};
 
 #[sorted]
-#[derive(Debug)]
+#[derive(ThisError, Debug)]
 pub enum Error {
+    #[error("failed to create block device: {0}")]
     BlockDeviceNew(base::Error),
+    #[error("requested file conversion not supported")]
     ConversionNotSupported,
+    #[error("failure in android sparse disk: {0}")]
     CreateAndroidSparseDisk(android_sparse::Error),
     #[cfg(feature = "composite-disk")]
+    #[error("failure in composite disk: {0}")]
     CreateCompositeDisk(composite::Error),
+    #[error("failure creating single file disk: {0}")]
     CreateSingleFileDisk(cros_async::AsyncError),
+    #[error("failure with fallocate: {0}")]
     Fallocate(cros_async::AsyncError),
+    #[error("failure with fsync: {0}")]
     Fsync(cros_async::AsyncError),
+    #[error("failure in qcow: {0}")]
     QcowError(qcow::Error),
+    #[error("failed to read data: {0}")]
     ReadingData(io::Error),
+    #[error("failed to read header: {0}")]
     ReadingHeader(io::Error),
+    #[error("failed to read to memory: {0}")]
     ReadToMem(cros_async::AsyncError),
+    #[error("failed to seek file: {0}")]
     SeekingFile(io::Error),
+    #[error("failed to set file size: {0}")]
     SettingFileSize(io::Error),
+    #[error("unknown disk type")]
     UnknownType,
+    #[error("failed to write from memory: {0}")]
     WriteFromMem(cros_async::AsyncError),
+    #[error("failed to write from vec: {0}")]
     WriteFromVec(cros_async::AsyncError),
+    #[error("failed to write data: {0}")]
     WritingData(io::Error),
 }
 
@@ -116,35 +134,6 @@ impl ToAsyncDisk for File {
     }
 }
 
-impl Display for Error {
-    #[remain::check]
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        use self::Error::*;
-
-        #[sorted]
-        match self {
-            BlockDeviceNew(e) => write!(f, "failed to create block device: {}", e),
-            ConversionNotSupported => write!(f, "requested file conversion not supported"),
-            CreateAndroidSparseDisk(e) => write!(f, "failure in android sparse disk: {}", e),
-            #[cfg(feature = "composite-disk")]
-            CreateCompositeDisk(e) => write!(f, "failure in composite disk: {}", e),
-            CreateSingleFileDisk(e) => write!(f, "failure creating single file disk: {}", e),
-            Fallocate(e) => write!(f, "failure with fallocate: {}", e),
-            Fsync(e) => write!(f, "failure with fsync: {}", e),
-            QcowError(e) => write!(f, "failure in qcow: {}", e),
-            ReadingData(e) => write!(f, "failed to read data: {}", e),
-            ReadingHeader(e) => write!(f, "failed to read header: {}", e),
-            ReadToMem(e) => write!(f, "failed to read to memory: {}", e),
-            SeekingFile(e) => write!(f, "failed to seek file: {}", e),
-            SettingFileSize(e) => write!(f, "failed to set file size: {}", e),
-            UnknownType => write!(f, "unknown disk type"),
-            WriteFromMem(e) => write!(f, "failed to write from memory: {}", e),
-            WriteFromVec(e) => write!(f, "failed to write from vec: {}", e),
-            WritingData(e) => write!(f, "failed to write data: {}", e),
-        }
-    }
-}
-
 /// The variants of image files on the host that can be used as virtual disks.
 #[derive(Debug, PartialEq, Eq)]
 pub enum ImageType {