minor: Implement common traits for OneOrManyWithParens

src/ast/mod.rs

@@ -20,6 +20,7 @@ use alloc::{
 };
 
 use core::fmt::{self, Display};
+use core::ops::Deref;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -993,7 +994,26 @@ impl fmt::Display for LambdaFunction {
 
 /// Encapsulates the common pattern in SQL where either one unparenthesized item
 /// such as an identifier or expression is permitted, or multiple of the same
-/// item in a parenthesized list.
+/// item in a parenthesized list. For accessing items regardless of the form,
+/// `OneOrManyWithParens` implements `Deref<Target = [T]>` and `IntoIterator`,
+/// so you can call slice methods on it and iterate over items
+/// # Examples
+/// Acessing as a slice:
+/// ```
+/// # use sqlparser::ast::OneOrManyWithParens;
+/// let one = OneOrManyWithParens::One("a");
+///
+/// assert_eq!(one[0], "a");
+/// assert_eq!(one.len(), 1);
+/// ```
+/// Iterating:
+/// ```
+/// # use sqlparser::ast::OneOrManyWithParens;
+/// let one = OneOrManyWithParens::One("a");
+/// let many = OneOrManyWithParens::Many(vec!["a", "b"]);
+///
+/// assert_eq!(one.into_iter().chain(many).collect::<Vec<_>>(), vec!["a", "a", "b"] );
+/// ```
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
@@ -1004,6 +1024,125 @@ pub enum OneOrManyWithParens<T> {
     Many(Vec<T>),
 }
 
+impl<T> Deref for OneOrManyWithParens<T> {
+    type Target = [T];
+
+    fn deref(&self) -> &[T] {
+        match self {
+            OneOrManyWithParens::One(one) => core::slice::from_ref(one),
+            OneOrManyWithParens::Many(many) => many,
+        }
+    }
+}
+
+impl<T> AsRef<[T]> for OneOrManyWithParens<T> {
+    fn as_ref(&self) -> &[T] {
+        self
+    }
+}
+
+impl<'a, T> IntoIterator for &'a OneOrManyWithParens<T> {
+    type Item = &'a T;
+    type IntoIter = core::slice::Iter<'a, T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+/// Owned iterator implementation of `OneOrManyWithParens`
+#[derive(Debug, Clone)]
+pub struct OneOrManyWithParensIntoIter<T> {
+    inner: OneOrManyWithParensIntoIterInner<T>,
+}
+
+#[derive(Debug, Clone)]
+enum OneOrManyWithParensIntoIterInner<T> {
+    One(core::iter::Once<T>),
+    Many(<Vec<T> as IntoIterator>::IntoIter),
+}
+
+impl<T> core::iter::FusedIterator for OneOrManyWithParensIntoIter<T>
+where
+    core::iter::Once<T>: core::iter::FusedIterator,
+    <Vec<T> as IntoIterator>::IntoIter: core::iter::FusedIterator,
+{
+}
+
+impl<T> core::iter::ExactSizeIterator for OneOrManyWithParensIntoIter<T>
+where
+    core::iter::Once<T>: core::iter::ExactSizeIterator,
+    <Vec<T> as IntoIterator>::IntoIter: core::iter::ExactSizeIterator,
+{
+}
+
+impl<T> core::iter::Iterator for OneOrManyWithParensIntoIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match &mut self.inner {
+            OneOrManyWithParensIntoIterInner::One(one) => one.next(),
+            OneOrManyWithParensIntoIterInner::Many(many) => many.next(),
+        }
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        match &self.inner {
+            OneOrManyWithParensIntoIterInner::One(one) => one.size_hint(),
+            OneOrManyWithParensIntoIterInner::Many(many) => many.size_hint(),
+        }
+    }
+
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        match self.inner {
+            OneOrManyWithParensIntoIterInner::One(one) => one.count(),
+            OneOrManyWithParensIntoIterInner::Many(many) => many.count(),
+        }
+    }
+
+    fn fold<B, F>(mut self, init: B, f: F) -> B
+    where
+        Self: Sized,
+        F: FnMut(B, Self::Item) -> B,
+    {
+        match &mut self.inner {
+            OneOrManyWithParensIntoIterInner::One(one) => one.fold(init, f),
+            OneOrManyWithParensIntoIterInner::Many(many) => many.fold(init, f),
+        }
+    }
+}
+
+impl<T> core::iter::DoubleEndedIterator for OneOrManyWithParensIntoIter<T> {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        match &mut self.inner {
+            OneOrManyWithParensIntoIterInner::One(one) => one.next_back(),
+            OneOrManyWithParensIntoIterInner::Many(many) => many.next_back(),
+        }
+    }
+}
+
+impl<T> IntoIterator for OneOrManyWithParens<T> {
+    type Item = T;
+
+    type IntoIter = OneOrManyWithParensIntoIter<T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        let inner = match self {
+            OneOrManyWithParens::One(one) => {
+                OneOrManyWithParensIntoIterInner::One(core::iter::once(one))
+            }
+            OneOrManyWithParens::Many(many) => {
+                OneOrManyWithParensIntoIterInner::Many(many.into_iter())
+            }
+        };
+
+        OneOrManyWithParensIntoIter { inner }
+    }
+}
+
 impl<T> fmt::Display for OneOrManyWithParens<T>
 where
     T: fmt::Display,
@@ -6919,4 +7058,178 @@ mod tests {
         });
         assert_eq!("INTERVAL '5' SECOND (1, 3)", format!("{interval}"));
     }
+
+    #[test]
+    fn test_one_or_many_with_parens_deref() {
+        use core::ops::Index;
+
+        let one = OneOrManyWithParens::One("a");
+
+        assert_eq!(one.deref(), &["a"]);
+        assert_eq!(<OneOrManyWithParens<_> as Deref>::deref(&one), &["a"]);
+
+        assert_eq!(one[0], "a");
+        assert_eq!(one.index(0), &"a");
+        assert_eq!(
+            <<OneOrManyWithParens<_> as Deref>::Target as Index<usize>>::index(&one, 0),
+            &"a"
+        );
+
+        assert_eq!(one.len(), 1);
+        assert_eq!(<OneOrManyWithParens<_> as Deref>::Target::len(&one), 1);
+
+        let many1 = OneOrManyWithParens::Many(vec!["b"]);
+
+        assert_eq!(many1.deref(), &["b"]);
+        assert_eq!(<OneOrManyWithParens<_> as Deref>::deref(&many1), &["b"]);
+
+        assert_eq!(many1[0], "b");
+        assert_eq!(many1.index(0), &"b");
+        assert_eq!(
+            <<OneOrManyWithParens<_> as Deref>::Target as Index<usize>>::index(&many1, 0),
+            &"b"
+        );
+
+        assert_eq!(many1.len(), 1);
+        assert_eq!(<OneOrManyWithParens<_> as Deref>::Target::len(&many1), 1);
+
+        let many2 = OneOrManyWithParens::Many(vec!["c", "d"]);
+
+        assert_eq!(many2.deref(), &["c", "d"]);
+        assert_eq!(
+            <OneOrManyWithParens<_> as Deref>::deref(&many2),
+            &["c", "d"]
+        );
+
+        assert_eq!(many2[0], "c");
+        assert_eq!(many2.index(0), &"c");
+        assert_eq!(
+            <<OneOrManyWithParens<_> as Deref>::Target as Index<usize>>::index(&many2, 0),
+            &"c"
+        );
+
+        assert_eq!(many2[1], "d");
+        assert_eq!(many2.index(1), &"d");
+        assert_eq!(
+            <<OneOrManyWithParens<_> as Deref>::Target as Index<usize>>::index(&many2, 1),
+            &"d"
+        );
+
+        assert_eq!(many2.len(), 2);
+        assert_eq!(<OneOrManyWithParens<_> as Deref>::Target::len(&many2), 2);
+    }
+
+    #[test]
+    fn test_one_or_many_with_parens_as_ref() {
+        let one = OneOrManyWithParens::One("a");
+
+        assert_eq!(one.as_ref(), &["a"]);
+        assert_eq!(<OneOrManyWithParens<_> as AsRef<_>>::as_ref(&one), &["a"]);
+
+        let many1 = OneOrManyWithParens::Many(vec!["b"]);
+
+        assert_eq!(many1.as_ref(), &["b"]);
+        assert_eq!(<OneOrManyWithParens<_> as AsRef<_>>::as_ref(&many1), &["b"]);
+
+        let many2 = OneOrManyWithParens::Many(vec!["c", "d"]);
+
+        assert_eq!(many2.as_ref(), &["c", "d"]);
+        assert_eq!(
+            <OneOrManyWithParens<_> as AsRef<_>>::as_ref(&many2),
+            &["c", "d"]
+        );
+    }
+
+    #[test]
+    fn test_one_or_many_with_parens_ref_into_iter() {
+        let one = OneOrManyWithParens::One("a");
+
+        assert_eq!(Vec::from_iter(&one), vec![&"a"]);
+
+        let many1 = OneOrManyWithParens::Many(vec!["b"]);
+
+        assert_eq!(Vec::from_iter(&many1), vec![&"b"]);
+
+        let many2 = OneOrManyWithParens::Many(vec!["c", "d"]);
+
+        assert_eq!(Vec::from_iter(&many2), vec![&"c", &"d"]);
+    }
+
+    #[test]
+    fn test_one_or_many_with_parens_value_into_iter() {
+        use core::iter::once;
+
+        //tests that our iterator implemented methods behaves exactly as it's inner iterator, at every step up to n calls to next/next_back
+        fn test_steps<I>(ours: OneOrManyWithParens<usize>, inner: I, n: usize)
+        where
+            I: IntoIterator<Item = usize, IntoIter: DoubleEndedIterator + Clone> + Clone,
+        {
+            fn checks<I>(ours: OneOrManyWithParensIntoIter<usize>, inner: I)
+            where
+                I: Iterator<Item = usize> + Clone + DoubleEndedIterator,
+            {
+                assert_eq!(ours.size_hint(), inner.size_hint());
+                assert_eq!(ours.clone().count(), inner.clone().count());
+
+                assert_eq!(
+                    ours.clone().fold(1, |a, v| a + v),
+                    inner.clone().fold(1, |a, v| a + v)
+                );
+
+                assert_eq!(Vec::from_iter(ours.clone()), Vec::from_iter(inner.clone()));
+                assert_eq!(
+                    Vec::from_iter(ours.clone().rev()),
+                    Vec::from_iter(inner.clone().rev())
+                );
+            }
+
+            let mut ours_next = ours.clone().into_iter();
+            let mut inner_next = inner.clone().into_iter();
+
+            for _ in 0..n {
+                checks(ours_next.clone(), inner_next.clone());
+
+                assert_eq!(ours_next.next(), inner_next.next());
+            }
+
+            let mut ours_next_back = ours.clone().into_iter();
+            let mut inner_next_back = inner.clone().into_iter();
+
+            for _ in 0..n {
+                checks(ours_next_back.clone(), inner_next_back.clone());
+
+                assert_eq!(ours_next_back.next_back(), inner_next_back.next_back());
+            }
+
+            let mut ours_mixed = ours.clone().into_iter();
+            let mut inner_mixed = inner.clone().into_iter();
+
+            for i in 0..n {
+                checks(ours_mixed.clone(), inner_mixed.clone());
+
+                if i % 2 == 0 {
+                    assert_eq!(ours_mixed.next_back(), inner_mixed.next_back());
+                } else {
+                    assert_eq!(ours_mixed.next(), inner_mixed.next());
+                }
+            }
+
+            let mut ours_mixed2 = ours.into_iter();
+            let mut inner_mixed2 = inner.into_iter();
+
+            for i in 0..n {
+                checks(ours_mixed2.clone(), inner_mixed2.clone());
+
+                if i % 2 == 0 {
+                    assert_eq!(ours_mixed2.next(), inner_mixed2.next());
+                } else {
+                    assert_eq!(ours_mixed2.next_back(), inner_mixed2.next_back());
+                }
+            }
+        }
+
+        test_steps(OneOrManyWithParens::One(1), once(1), 3);
+        test_steps(OneOrManyWithParens::Many(vec![2]), vec![2], 3);
+        test_steps(OneOrManyWithParens::Many(vec![3, 4]), vec![3, 4], 4);
+    }
 }