feat: add a simplify for error messages

Author: Eh2406

src/range.rs

@@ -203,22 +203,55 @@ impl<V: Ord> Range<V> {
     pub fn contains(&self, v: &V) -> bool {
         for segment in self.segments.iter() {
             if match segment {
-                (Unbounded, Unbounded) => true,
-                (Unbounded, Included(end)) => v <= end,
-                (Unbounded, Excluded(end)) => v < end,
-                (Included(start), Unbounded) => v >= start,
-                (Included(start), Included(end)) => v >= start && v <= end,
-                (Included(start), Excluded(end)) => v >= start && v < end,
-                (Excluded(start), Unbounded) => v > start,
-                (Excluded(start), Included(end)) => v > start && v <= end,
-                (Excluded(start), Excluded(end)) => v > start && v < end,
+                (Excluded(start), _) => v <= start,
+                (Included(start), _) => v < start,
+                (Unbounded, _) => false,
+            } {
+                return false;
+            }
+            if match segment {
+                (_, Unbounded) => true,
+                (_, Included(end)) => v <= end,
+                (_, Excluded(end)) => v < end,
             } {
                 return true;
             }
         }
         false
     }
 
+    /// Returns true if the this Range contains the specified values.
+    ///
+    /// The `versions` iterator must be sorted.
+    /// Functionally equivalent to `versions.map(|v| self.contains(v))`.
+    /// Except it runs in `O(size_of_range + len_of_versions)` not `O(size_of_range * len_of_versions)`
+    pub fn contains_many<'s, I>(&'s self, versions: I) -> impl Iterator<Item = bool> + 's
+    where
+        I: Iterator<Item = &'s V> + 's,
+        V: 's,
+    {
+        versions.scan(0, |i, v| {
+            while let Some(segment) = self.segments.get(*i) {
+                if match segment {
+                    (Excluded(start), _) => v <= start,
+                    (Included(start), _) => v < start,
+                    (Unbounded, _) => false,
+                } {
+                    return Some(false);
+                }
+                if match segment {
+                    (_, Unbounded) => true,
+                    (_, Included(end)) => v <= end,
+                    (_, Excluded(end)) => v < end,
+                } {
+                    return Some(true);
+                }
+                *i += 1;
+            }
+            Some(false)
+        })
+    }
+
     /// Construct a simple range from anything that impls [RangeBounds] like `v1..v2`.
     pub fn from_range_bounds<R, IV>(bounds: R) -> Self
     where
@@ -321,6 +354,71 @@ impl<V: Ord + Clone> Range<V> {
 
         Self { segments }.check_invariants()
     }
+
+    /// Returns a simpler Range that contains the same versions
+    ///
+    /// For every one of the Versions provided in versions the existing range and
+    /// the simplified range will agree on whether it is contained.
+    /// The simplified version may include or exclude versions that are not in versions as the implementation wishes.
+    /// For example:
+    ///  - If all the versions are contained in the original than the range will be simplified to `full`.
+    ///  - If none of the versions are contained in the original than the range will be simplified to `empty`.
+    ///
+    /// If versions are not sorted the correctness of this function is not guaranteed.
+    pub fn simplify<'a, I>(&self, versions: I) -> Self
+    where
+        I: Iterator<Item = &'a V>,
+        V: 'a,
+    {
+        // First we determined for each version if there is a segment that makes it match.
+        let mut matches = versions.scan(0, |i, v| {
+            while let Some(segment) = self.segments.get(*i) {
+                if match segment {
+                    (Excluded(start), _) => v <= start,
+                    (Included(start), _) => v < start,
+                    (Unbounded, _) => false,
+                } {
+                    return Some(None);
+                }
+                if match segment {
+                    (_, Unbounded) => true,
+                    (_, Included(end)) => v <= end,
+                    (_, Excluded(end)) => v < end,
+                } {
+                    return Some(Some(*i));
+                }
+                *i += 1;
+            }
+            Some(None)
+        });
+        let mut segments = SmallVec::Empty;
+        // If the first version matched, then the lower bound of that segment is not needed
+        let mut seg = if let Some(Some(ver)) = matches.next() {
+            Some((&Unbounded, &self.segments[ver].1))
+        } else {
+            None
+        };
+        for ver in matches {
+            if let Some(ver) = ver {
+                // As long as were still matching versions, we keep merging into the currently matching segment
+                seg = Some((
+                    seg.map(|(s, _)| s).unwrap_or(&self.segments[ver].0),
+                    &self.segments[ver].1,
+                ));
+            } else {
+                // If we have found a version that doesn't match, then right the merge segment and prepare for a new one.
+                if let Some((s, e)) = seg {
+                    segments.push((s.clone(), e.clone()));
+                }
+                seg = None;
+            }
+        }
+        // If the last version matched, then write out the merged segment but the upper bound is not needed.
+        if let Some((s, _)) = seg {
+            segments.push((s.clone(), Unbounded));
+        }
+        Self { segments }.check_invariants()
+    }
 }
 
 impl<T: Debug + Display + Clone + Eq + Ord> VersionSet for Range<T> {
@@ -600,5 +698,49 @@ pub mod tests {
             let rv2: Range<u32> = rv.bounding_range().map(Range::from_range_bounds::<_, u32>).unwrap_or_else(Range::empty);
             assert_eq!(rv, rv2);
         }
+
+        #[test]
+        fn contains(range in strategy(), versions in vec![version_strat()]) {
+            fn direct_implementation_of_contains(s: &Range<u32>, v: &u32) -> bool {
+                for segment in s.segments.iter() {
+                    if match segment {
+                        (Unbounded, Unbounded) => true,
+                        (Unbounded, Included(end)) => v <= end,
+                        (Unbounded, Excluded(end)) => v < end,
+                        (Included(start), Unbounded) => v >= start,
+                        (Included(start), Included(end)) => v >= start && v <= end,
+                        (Included(start), Excluded(end)) => v >= start && v < end,
+                        (Excluded(start), Unbounded) => v > start,
+                        (Excluded(start), Included(end)) => v > start && v <= end,
+                        (Excluded(start), Excluded(end)) => v > start && v < end,
+                    } {
+                        return true;
+                    }
+                }
+                false
+            }
+
+            for v in versions {
+                assert_eq!(range.contains(&v), direct_implementation_of_contains(&range, &v));
+            }
+        }
+
+        #[test]
+        fn contains_many(range in strategy(), mut versions in vec![version_strat()]) {
+            versions.sort();
+            for (a, b) in versions.iter().map(|v| range.contains(v)).zip(range.contains_many(versions.iter())) {
+                assert_eq!(a, b);
+            }
+        }
+
+        #[test]
+        fn simplify(range in strategy(), mut versions in vec![version_strat()]) {
+            versions.sort();
+            let simp = range.simplify(versions.iter());
+            for v in versions {
+                assert_eq!(range.contains(&v), simp.contains(&v));
+            }
+            assert!(simp.segments.len() <= range.segments.len())
+        }
     }
 }