refactor(hardlink): move DeviceNumber into device module, add dev to error types

- Move DeviceNumber from device_number.rs into device.rs alongside
  DeviceBoundary, mirroring the InodeNumber-in-inode.rs pattern
- Add dev: DeviceNumber to SizeConflictError and NumberOfLinksConflictError
  so error messages identify the exact (inode, device) pair

https://claude.ai/code/session_01QP9wZyoZcGmJsEsA66ZRok

Author: claude

src/device.rs

@@ -1,3 +1,8 @@
+use derive_more::{Display, From, Into, LowerHex, Octal, UpperHex};
+
+#[cfg(feature = "json")]
+use serde::{Deserialize, Serialize};
+
 /// Whether to cross device boundary into a different filesystem.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum DeviceBoundary {
@@ -15,3 +20,22 @@ impl DeviceBoundary {
         }
     }
 }
+
+/// The device number of a filesystem.
+#[derive(
+    Debug, Display, LowerHex, UpperHex, Octal, Clone, Copy, PartialEq, Eq, Hash, From, Into,
+)]
+#[cfg_attr(feature = "json", derive(Deserialize, Serialize))]
+pub struct DeviceNumber(u64);
+
+/// POSIX-exclusive functions.
+#[cfg(unix)]
+impl DeviceNumber {
+    /// Get device number of a [`std::fs::Metadata`].
+    #[inline]
+    pub fn get(stats: &std::fs::Metadata) -> Self {
+        use pipe_trait::Pipe;
+        use std::os::unix::fs::MetadataExt;
+        stats.dev().pipe(DeviceNumber)
+    }
+}

src/device_number.rs

@@ -4,7 +4,7 @@ use super::{
 };
 use crate::{
     data_tree::DataTree,
-    device_number::DeviceNumber,
+    device::DeviceNumber,
     inode::InodeNumber,
     os_string_display::OsStringDisplay,
     reporter::{event::HardlinkDetection, Event, Reporter},

src/hardlink/aware.rs

@@ -9,7 +9,7 @@ pub use summary::Summary;
 pub use Reflection as HardlinkListReflection;
 pub use Summary as SharedLinkSummary;
 
-use crate::{device_number::DeviceNumber, hardlink::LinkPathList, inode::InodeNumber, size};
+use crate::{device::DeviceNumber, hardlink::LinkPathList, inode::InodeNumber, size};
 use dashmap::DashMap;
 use derive_more::{Display, Error};
 use smart_default::SmartDefault;
@@ -78,31 +78,27 @@ impl<Size> HardlinkList<Size> {
     }
 }
 
-/// Error that occurs when a different size was detected for the same [`ino`][ino].
-///
-/// <!-- Should have been `std::os::unix::fs::MetadataExt::ino` but it would error on Windows -->
-/// [ino]: https://doc.rust-lang.org/std/os/unix/fs/trait.MetadataExt.html#tymethod.ino
+/// Error that occurs when a different size was detected for the same inode.
 #[derive(Debug, Display, Error)]
 #[cfg_attr(test, derive(PartialEq, Eq))]
 #[display(bound(Size: Debug))]
-#[display("Size for inode {ino} changed from {recorded:?} to {detected:?}")]
+#[display("Size for inode {ino} on device {dev} changed from {recorded:?} to {detected:?}")]
 pub struct SizeConflictError<Size> {
     pub ino: InodeNumber,
+    pub dev: DeviceNumber,
     pub recorded: Size,
     pub detected: Size,
 }
 
-/// Error that occurs when a different [`nlink`][nlink] was detected for the same [`ino`][ino].
-///
-/// <!-- Should have been `std::os::unix::fs::MetadataExt::nlink` but it would error on Windows -->
-/// [nlink]: https://doc.rust-lang.org/std/os/unix/fs/trait.MetadataExt.html#tymethod.nlink
-/// <!-- Should have been `std::os::unix::fs::MetadataExt::ino` but it would error on Windows -->
-/// [ino]: https://doc.rust-lang.org/std/os/unix/fs/trait.MetadataExt.html#tymethod.ino
+/// Error that occurs when a different number of links was detected for the same inode.
 #[derive(Debug, Display, Error)]
 #[cfg_attr(test, derive(PartialEq, Eq))]
-#[display("Number of links of inode {ino} changed from {recorded:?} to {detected:?}")]
+#[display(
+    "Number of links of inode {ino} on device {dev} changed from {recorded:?} to {detected:?}"
+)]
 pub struct NumberOfLinksConflictError {
     pub ino: InodeNumber,
+    pub dev: DeviceNumber,
     pub recorded: u64,
     pub detected: u64,
 }
@@ -139,6 +135,7 @@ where
                 if size != recorded.size {
                     assertions = Err(AddError::SizeConflict(SizeConflictError {
                         ino,
+                        dev,
                         recorded: recorded.size,
                         detected: size,
                     }));
@@ -149,6 +146,7 @@ where
                     assertions = Err(AddError::NumberOfLinksConflict(
                         NumberOfLinksConflictError {
                             ino,
+                            dev,
                             recorded: recorded.links,
                             detected: links,
                         },

src/hardlink/hardlink_list.rs

@@ -1,5 +1,5 @@
 use super::{HardlinkList, InodeKey, Value};
-use crate::{device_number::DeviceNumber, hardlink::LinkPathList, inode::InodeNumber};
+use crate::{device::DeviceNumber, hardlink::LinkPathList, inode::InodeNumber};
 use dashmap::{iter::Iter as DashIter, mapref::multiple::RefMulti};
 use pipe_trait::Pipe;
 

src/hardlink/hardlink_list/iter.rs

@@ -1,5 +1,5 @@
 use super::{HardlinkList, InodeKey, Value};
-use crate::{device_number::DeviceNumber, hardlink::LinkPathListReflection, inode::InodeNumber};
+use crate::{device::DeviceNumber, hardlink::LinkPathListReflection, inode::InodeNumber};
 use dashmap::DashMap;
 use derive_more::{Display, Error, Into, IntoIterator};
 use into_sorted::IntoSortedUnstable;

src/hardlink/hardlink_list/reflection.rs

@@ -127,6 +127,7 @@ fn detect_size_change() {
         .expect_err("add the second path");
     let expected = AddError::SizeConflict(SizeConflictError {
         ino: 123.into(),
+        dev: 0.into(),
         recorded: 100.into(),
         detected: 110.into(),
     });
@@ -143,6 +144,7 @@ fn detect_number_of_links_change() {
         .expect_err("add the second path");
     let expected = AddError::NumberOfLinksConflict(NumberOfLinksConflictError {
         ino: 123.into(),
+        dev: 0.into(),
         recorded: 1,
         detected: 2,
     });

src/hardlink/hardlink_list/test.rs

@@ -41,7 +41,6 @@ pub use clap_utilities;
 pub mod bytes_format;
 pub mod data_tree;
 pub mod device;
-pub mod device_number;
 pub mod fs_tree_builder;
 pub mod get_size;
 pub mod hardlink;

src/lib.rs

@@ -586,7 +586,7 @@ pub fn read_inode_number(path: &Path) -> u64 {
 
 /// Read [dev](std::os::unix::fs::MetadataExt::dev) of a path.
 #[cfg(unix)]
-pub fn read_device_number(path: &Path) -> parallel_disk_usage::device_number::DeviceNumber {
+pub fn read_device_number(path: &Path) -> parallel_disk_usage::device::DeviceNumber {
     use std::os::unix::fs::MetadataExt;
     path.pipe(symlink_metadata)
         .unwrap_or_else(|error| panic!("Can't read metadata at {path:?}: {error}"))