fix(postgres): case-aware type name equality

Author: abonander

sqlx-postgres/src/type_info.rs

@@ -1154,7 +1154,103 @@ impl PartialEq<PgType> for PgType {
             true
         } else {
             // Otherwise, perform a match on the name
-            self.name().eq_ignore_ascii_case(other.name())
+            name_eq(self.name(), other.name())
         }
     }
 }
+
+/// Check type names for equality, respecting Postgres' case sensitivity rules for identifiers.
+///
+/// https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
+fn name_eq(name1: &str, name2: &str) -> bool {
+    // Cop-out of processing Unicode escapes by just using string equality.
+    if name1.starts_with("U&") {
+        // If `name2` doesn't start with `U&` this will automatically be `false`.
+        return name1 == name2;
+    }
+
+    let mut chars1 = identifier_chars(name1);
+    let mut chars2 = identifier_chars(name2);
+
+    while let (Some(a), Some(b)) = (chars1.next(), chars2.next()) {
+        if !a.eq(&b) {
+            return false;
+        }
+    }
+
+    chars1.next().is_none() && chars2.next().is_none()
+}
+
+struct IdentifierChar {
+    ch: char,
+    case_sensitive: bool,
+}
+
+impl IdentifierChar {
+    fn eq(&self, other: &Self) -> bool {
+        if self.case_sensitive || other.case_sensitive {
+            self.ch == other.ch
+        } else {
+            self.ch.eq_ignore_ascii_case(&other.ch)
+        }
+    }
+}
+
+/// Return an iterator over all significant characters of an identifier.
+///
+/// Ignores non-escaped quotation marks.
+fn identifier_chars(ident: &str) -> impl Iterator<Item = IdentifierChar> + '_ {
+    let mut case_sensitive = false;
+    let mut last_char_quote = false;
+
+    ident.chars().filter_map(move |ch| {
+        if ch == '"' {
+            if last_char_quote {
+                last_char_quote = false;
+            } else {
+                last_char_quote = true;
+                return None;
+            }
+        } else if last_char_quote {
+            last_char_quote = false;
+            case_sensitive = !case_sensitive;
+        }
+
+        Some(IdentifierChar { ch, case_sensitive })
+    })
+}
+
+#[test]
+fn test_name_eq() {
+    let test_values = [
+        ("foo", "foo", true),
+        ("foo", "Foo", true),
+        ("foo", "FOO", true),
+        ("foo", r#""foo""#, true),
+        ("foo", r#""Foo""#, false),
+        ("foo", "foo.foo", false),
+        ("foo.foo", "foo.foo", true),
+        ("foo.foo", "foo.Foo", true),
+        ("foo.foo", "foo.FOO", true),
+        ("foo.foo", "Foo.foo", true),
+        ("foo.foo", "Foo.Foo", true),
+        ("foo.foo", "FOO.FOO", true),
+        ("foo.foo", "foo", false),
+        ("foo.foo", r#"foo."foo""#, true),
+        ("foo.foo", r#"foo."Foo""#, false),
+        ("foo.foo", r#"foo."FOO""#, false),
+    ];
+
+    for (left, right, eq) in test_values {
+        assert_eq!(
+            name_eq(left, right),
+            eq,
+            "failed check for name_eq({left:?}, {right:?})"
+        );
+        assert_eq!(
+            name_eq(right, left),
+            eq,
+            "failed check for name_eq({right:?}, {left:?})"
+        );
+    }
+}