From 042e537ca835245083ae864a7448f86763acb2ef Mon Sep 17 00:00:00 2001
From: Jeffrey Finkelstein <jeffrey.finkelstein@protonmail.com>
Date: Sat, 12 Feb 2022 20:54:47 -0500
Subject: [PATCH] df: refactor is_included(), mount_info_lt() funcs

Factor two helper functions, `is_included()` and `mount_info_lt()`,
from the `filter_mount_list()` function.
---
 src/uu/df/src/df.rs | 94 ++++++++++++++++++++++++++++-----------------
 1 file changed, 59 insertions(+), 35 deletions(-)

diff --git a/src/uu/df/src/df.rs b/src/uu/df/src/df.rs
index a51966d9e..b4153f1af 100644
--- a/src/uu/df/src/df.rs
+++ b/src/uu/df/src/df.rs
@@ -161,6 +161,63 @@ impl Filesystem {
     }
 }
 
+/// Whether to display the mount info given the inclusion settings.
+fn is_included(mi: &MountInfo, paths: &[String], opt: &Options) -> bool {
+    // Don't show remote filesystems if `--local` has been given.
+    if mi.remote && opt.show_local_fs {
+        return false;
+    }
+
+    // Don't show pseudo filesystems unless `--all` has been given.
+    if mi.dummy && !opt.show_all_fs && !opt.show_listed_fs {
+        return false;
+    }
+
+    // Don't show filesystems if they have been explicitly excluded.
+    if !opt.fs_selector.should_select(&mi.fs_type) {
+        return false;
+    }
+
+    // Don't show filesystems other than the ones specified on the
+    // command line, if any.
+    if !paths.is_empty() && !paths.contains(&mi.mount_dir) {
+        return false;
+    }
+
+    true
+}
+
+/// Whether the mount info in `m2` should be prioritized over `m1`.
+///
+/// The "lt" in the function name is in analogy to the
+/// [`std::cmp::PartialOrd::lt`].
+fn mount_info_lt(m1: &MountInfo, m2: &MountInfo) -> bool {
+    // let "real" devices with '/' in the name win.
+    if m1.dev_name.starts_with('/') && !m2.dev_name.starts_with('/') {
+        return false;
+    }
+
+    let m1_nearer_root = m1.mount_dir.len() < m2.mount_dir.len();
+    // With bind mounts, prefer items nearer the root of the source
+    let m2_below_root = !m1.mount_root.is_empty()
+        && !m2.mount_root.is_empty()
+        && m1.mount_root.len() > m2.mount_root.len();
+    // let points towards the root of the device win.
+    if m1_nearer_root && !m2_below_root {
+        return false;
+    }
+
+    // let an entry over-mounted on a new device win, but only when
+    // matching an existing mnt point, to avoid problematic
+    // replacement when given inaccurate mount lists, seen with some
+    // chroot environments for example.
+    if m1.dev_name != m2.dev_name && m1.mount_dir == m2.mount_dir {
+        return false;
+    }
+
+    true
+}
+
 /// Keep only the specified subset of [`MountInfo`] instances.
 ///
 /// If `paths` is non-empty, this function excludes any [`MountInfo`]
@@ -174,24 +231,7 @@ impl Filesystem {
 fn filter_mount_list(vmi: Vec<MountInfo>, paths: &[String], opt: &Options) -> Vec<MountInfo> {
     let mut mount_info_by_id = HashMap::<String, Cell<MountInfo>>::new();
     for mi in vmi {
-        // Don't show remote filesystems if `--local` has been given.
-        if mi.remote && opt.show_local_fs {
-            continue;
-        }
-
-        // Don't show pseudo filesystems unless `--all` has been given.
-        if mi.dummy && !opt.show_all_fs && !opt.show_listed_fs {
-            continue;
-        }
-
-        // Don't show filesystems if they have been explicitly excluded.
-        if !opt.fs_selector.should_select(&mi.fs_type) {
-            continue;
-        }
-
-        // Don't show filesystems other than the ones specified on the
-        // command line, if any.
-        if !paths.is_empty() && !paths.contains(&mi.mount_dir) {
+        if !is_included(&mi, paths, opt) {
             continue;
         }
 
@@ -207,23 +247,7 @@ fn filter_mount_list(vmi: Vec<MountInfo>, paths: &[String], opt: &Options) -> Ve
         // then check if we need to update it or keep the previously
         // seen one.
         let seen = mount_info_by_id[&id].replace(mi.clone());
-        let target_nearer_root = seen.mount_dir.len() > mi.mount_dir.len();
-        // With bind mounts, prefer items nearer the root of the source
-        let source_below_root = !seen.mount_root.is_empty()
-            && !mi.mount_root.is_empty()
-            && seen.mount_root.len() < mi.mount_root.len();
-        // let "real" devices with '/' in the name win.
-        if (!mi.dev_name.starts_with('/') || seen.dev_name.starts_with('/'))
-            // let points towards the root of the device win.
-            && (!target_nearer_root || source_below_root)
-            // let an entry over-mounted on a new device win...
-            && (seen.dev_name == mi.dev_name
-                /* ... but only when matching an existing mnt point,
-                to avoid problematic replacement when given
-                inaccurate mount lists, seen with some chroot
-                environments for example.  */
-                || seen.mount_dir != mi.mount_dir)
-        {
+        if mount_info_lt(&mi, &seen) {
             mount_info_by_id[&id].replace(seen);
         }
     }