first stab at normalization can reduce 245 version, but… (#16)

…that's unexpectedly low. What's the matter here?

src/index/diff/delegate.rs

@@ -3,10 +3,11 @@ use crate::{Change, CrateVersion};
 use git_repository as git;
 use git_repository::diff::tree::visit::Action;
 use similar::ChangeTag;
+use std::collections::BTreeSet;
 
 pub(crate) struct Delegate<'repo> {
     changes: Vec<Change>,
-    deletes: Vec<CrateVersion>,
+    delete_version_ids: BTreeSet<u64>,
     file_name: git::bstr::BString,
     err: Option<Error>,
     repo: &'repo git::Repository,
@@ -16,7 +17,7 @@ impl<'repo> Delegate<'repo> {
     pub fn from_repo(repo: &'repo git::Repository) -> Self {
         Delegate {
             changes: Vec::new(),
-            deletes: Vec::new(),
+            delete_version_ids: BTreeSet::new(),
             err: None,
             file_name: Default::default(),
             repo,
@@ -74,7 +75,7 @@ impl<'repo> Delegate<'repo> {
                                         Change::Added(version)
                                     });
                                 } else {
-                                    self.deletes.push(version);
+                                    self.delete_version_ids.insert(version.id());
                                 }
                             }
                             ChangeTag::Equal => {}
@@ -85,15 +86,21 @@ impl<'repo> Delegate<'repo> {
         }
         Ok(())
     }
-    pub fn into_result(self) -> Result<Vec<Change>, Error> {
-        // assert_eq!(
-        //     self.deletes.len(),
-        //     0,
-        //     "TODO: handle apparent version deletions"
-        // );
+    pub fn into_result(mut self) -> Result<Vec<Change>, Error> {
         match self.err {
             Some(err) => Err(err),
-            None => Ok(self.changes),
+            None => {
+                if !self.delete_version_ids.is_empty() {
+                    let deleted_version_ids = &self.delete_version_ids;
+                    self.changes.retain(|change| match change {
+                        Change::Added(v) | Change::Yanked(v) => {
+                            !deleted_version_ids.contains(&v.id())
+                        }
+                        Change::Deleted { .. } => true,
+                    })
+                }
+                Ok(self.changes)
+            }
         }
     }
 }

src/types.rs

@@ -2,6 +2,7 @@ use std::collections::HashMap;
 
 use git_repository as git;
 use std::fmt;
+use std::hash::{Hash, Hasher};
 
 /// A wrapper for a repository of the crates.io index.
 pub struct Index {
@@ -88,8 +89,22 @@ pub struct CrateVersion {
     pub dependencies: Vec<Dependency>,
 }
 
+impl CrateVersion {
+    pub(crate) fn id(&self) -> u64 {
+        let mut s = std::collections::hash_map::DefaultHasher::new();
+        self.name.hash(&mut s);
+        self.yanked.hash(&mut s);
+        self.version.hash(&mut s);
+        self.checksum.hash(&mut s);
+        self.dependencies.hash(&mut s);
+        s.finish()
+    }
+}
+
 /// A single dependency of a specific crate version
-#[derive(Clone, serde::Serialize, serde::Deserialize, Ord, PartialOrd, Eq, PartialEq, Debug)]
+#[derive(
+    Clone, serde::Serialize, serde::Deserialize, Ord, PartialOrd, Eq, PartialEq, Debug, Hash,
+)]
 pub struct Dependency {
     /// The crate name
     pub name: String,

tests/index/changes_between_commits.rs

@@ -71,7 +71,7 @@ fn normalization() -> crate::Result {
     let changes = changes(index_ro()?, ":/normalize")?;
     assert_eq!(
         changes.len(),
-        2356, // should be 0
+        2111, // should be 0
         "normalization changes the representation, but the data itself stays the same, BUT we can't do it yet"
     );
     Ok(())

tests/index/mod.rs

@@ -84,7 +84,7 @@ fn quick_changes_since_last_fetch() -> crate::Result {
         "seen branch was updated again"
     );
     assert_eq!(
-        num_seen_after_reset, 2357,
+        num_seen_after_reset, 2112,
         "normalization has no changes, but the commit before has one"
     );