Add --dev flag to stay on the same filesystem by KSXGitHub · Pull Request #349 · KSXGitHub/parallel-disk-usage

KSXGitHub · 2026-03-11T00:59:18Z

Summary

This PR adds a new --dev command-line flag that restricts directory traversal to a single filesystem, preventing the tool from crossing mount points. This is useful when analyzing disk usage on systems with multiple mounted filesystems.

Key Changes

New --dev CLI argument: Added to Args struct with platform-specific visibility (POSIX only)
Device ID tracking: Implemented get_root_dev() function to retrieve the device ID of the root path using MetadataExt::dev() on Unix systems
Filesystem filtering: Modified FsTreeBuilder to skip entries on different filesystems when root_dev is set
Validation: Added checks to ensure --dev is only used on Unix platforms and cannot be combined with multiple path arguments
Error handling: Added DevArgConflict error variant for invalid flag combinations and UnsupportedFeature::Dev for non-Unix platforms
Test updates: Updated all test cases to include the new root_dev: None parameter in builder initialization
Documentation: Updated help text and completion scripts to include the new flag

Implementation Details

The feature is Unix-only and hidden from help text on non-Unix platforms
Device ID comparison is performed during tree traversal to skip directories on different filesystems
The macro-based run! pattern was extended to handle the new dev parameter across all size getter and progress combinations
Proper conditional compilation ensures the feature gracefully degrades on unsupported platforms

https://claude.ai/code/session_011HRevtBX4rP4YfBdapPFam

Add a --dev flag (POSIX only) that prevents pdu from crossing mount points during directory traversal. When active, entries whose st_dev differs from the root directory's st_dev are skipped entirely. - Add `dev` field to Args with clap integration (hidden on non-unix) - Add DevArgConflict runtime error when --dev is used with >1 path - Add UnsupportedFeature::Dev for non-unix platforms - Add root_dev field to FsTreeBuilder and Sub for device filtering - Add dev dimension to the run! macro (24 branches on unix) - Regenerate shell completions and help exports https://claude.ai/code/session_011HRevtBX4rP4YfBdapPFam

Copilot

Pull request overview

Adds a new --dev CLI flag to restrict filesystem traversal to the same device (avoid crossing mount points), by computing a root device ID and filtering traversal based on MetadataExt::dev() on Unix.

Changes:

Adds --dev to CLI args with Unix-only behavior (hidden and rejected on non-Unix).
Threads root_dev: Option<u64> through App → Sub → FsTreeBuilder and uses it to stop traversal into other devices.
Updates runtime errors/exit codes and refreshes help text, completion scripts, usage docs, and tests.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`src/args.rs`	Adds the `--dev` flag to CLI parsing (hidden on non-Unix).
`src/app.rs`	Validates `--dev`, computes `root_dev`, and expands the `run!` macro matrix to include dev on/off variants.
`src/app/sub.rs`	Passes `root_dev` into `FsTreeBuilder` during traversal.
`src/fs_tree_builder.rs`	Implements device-ID filtering during metadata collection to prevent crossing filesystems.
`src/runtime_error.rs`	Adds `DevArgConflict` and `UnsupportedFeature::Dev`, updates exit code mapping.
`tests/usual_cli.rs`	Updates builder struct literals for the new `root_dev` field.
`tests/json.rs`	Updates builder struct literal for the new `root_dev` field.
`tests/cli_errors.rs`	Updates builder struct literal for the new `root_dev` field.
`tests/_utils.rs`	Updates helper builder struct literal for the new `root_dev` field.
`exports/short.help`	Documents `--dev` in short help export.
`exports/long.help`	Documents `--dev` in long help export.
`exports/completion.*`	Adds `--dev` to shell completion outputs.
`USAGE.md`	Adds `--dev` documentation entry.

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src/fs_tree_builder.rs

Copilot · 2026-03-11T01:06:32Z

src/fs_tree_builder.rs

    pub reporter: &'a Report,
    /// Deepest level of descendant display in the graph. The sizes beyond the max depth still count toward total.
    pub max_depth: u64,
+    /// Device ID of the root directory. When `Some`, entries on different devices are skipped.


The root_dev field doc comment implies it works on all platforms, but the actual filtering logic is behind #[cfg(unix)] and is a no-op on non-Unix builds. Please clarify in the doc comment that this filtering is Unix-only (or gate the field/docs accordingly) to avoid misleading library users on Windows.

Suggested change

/// Device ID of the root directory. When `Some`, entries on different devices are skipped.

/// Device ID of the root directory.

///

/// On Unix, when this is `Some`, entries on different devices are skipped.

/// On non-Unix platforms this field is currently ignored and has no effect.

Copilot · 2026-03-11T01:06:32Z

src/fs_tree_builder.rs

+                        // When --dev is active, skip entries on different filesystems
+                        #[cfg(unix)]
+                        if let Some(root_dev) = root_dev {
+                            use std::os::unix::fs::MetadataExt;
+                            if stats.dev() != root_dev {
+                                return Info {
+                                    size: Size::default(),
+                                    children: Vec::new(),
+                                };
+                            }


This --dev path check returns an empty Info (size=0, no children), which stops traversal but still keeps the mountpoint entry in the resulting DataTree with a zero size. If the intended behavior is to truly skip the entry (omit it from output entirely), the filtering likely needs to happen at the parent read_dir stage (or TreeBuilder/Info needs an explicit “skip node” mechanism). If keeping the node is intended, consider adjusting the comment to say “do not traverse into” rather than “skip entries”.

Copilot · 2026-03-11T01:06:32Z

src/app/sub.rs

    pub min_ratio: Fraction,
    /// Preserve order of entries.
    pub no_sort: bool,
+    /// Device ID of the root directory. When `Some`, entries on different devices are skipped.


root_dev is documented as skipping entries on different devices, but on non-Unix platforms the dev-based filtering is not compiled in (and --dev is rejected). Consider clarifying in this field doc comment that it’s only meaningful on Unix, to keep the public Sub API accurate.

Suggested change

/// Device ID of the root directory. When `Some`, entries on different devices are skipped.

/// Device ID of the root directory. On Unix, when `Some`, entries on different devices are

/// skipped. On non-Unix platforms this field is ignored and has no effect.

Copilot · 2026-03-11T01:06:33Z

src/app.rs

+        if self.args.dev && self.args.files.len() > 1 {
+            return Err(RuntimeError::DevArgConflict);
+        }


New behavior is introduced here (--dev validation and the DevArgConflict error), but there doesn’t appear to be a corresponding CLI test ensuring the error triggers (and that --dev is wired through the run! matrix). Adding a small test case (e.g., pdu --dev path1 path2 expecting DevArgConflict) would help prevent regressions when the macro arm list changes.

root_dev is only used inside a #[cfg(unix)] block, so it triggers an unused variable warning on Windows builds. Add #[allow(unused_variables)] to the destructuring to fix CI. https://claude.ai/code/session_011HRevtBX4rP4YfBdapPFam

KSXGitHub requested a review from Copilot March 11, 2026 00:59

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Add --dev flag to stay on the same filesystem#349

Add --dev flag to stay on the same filesystem#349
KSXGitHub wants to merge 2 commits intoKSXGitHub:masterfrom
khai-slop-labs:claude/add-dev-flag-wncIS

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	/// Device ID of the root directory. When `Some`, entries on different devices are skipped.
	/// Device ID of the root directory. On Unix, when `Some`, entries on different devices are
	/// skipped. On non-Unix platforms this field is ignored and has no effect.

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KSXGitHub commented Mar 11, 2026

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