[Variant] Enahcne bracket access for VariantPath

parquet-variant/src/path.rs

@@ -75,14 +75,15 @@ use std::{borrow::Cow, ops::Deref};
 /// assert_eq!(path[1], VariantPathElement::field("bar"));
 /// ```
 ///
-/// # Example: Accessing filed with bracket
+/// # Example: Accessing field with bracket
 /// ```
 /// # use parquet_variant::{VariantPath, VariantPathElement};
-/// let path = VariantPath::try_from("a[b.c].d[2]").unwrap();
+/// let path = VariantPath::try_from("a['b.c'].d[2]['3']").unwrap();
 /// let expected = VariantPath::from_iter([VariantPathElement::field("a"),
 ///     VariantPathElement::field("b.c"),
 ///     VariantPathElement::field("d"),
-///     VariantPathElement::index(2)]);
+///     VariantPathElement::index(2),
+///     VariantPathElement::field("3")]);
 /// assert_eq!(path, expected)
 #[derive(Debug, Clone, PartialEq, Default)]
 pub struct VariantPath<'a>(Vec<VariantPathElement<'a>>);
@@ -287,11 +288,22 @@ mod tests {
         assert_eq!(path, expected);
 
         // invalid index will be treated as field
-        let path = VariantPath::try_from("foo.bar[abc]").unwrap();
+        let path = VariantPath::try_from("foo.bar['abc'][\"def\"]").unwrap();
         let expected = VariantPath::from_iter([
             VariantPathElement::field("foo"),
             VariantPathElement::field("bar"),
             VariantPathElement::field("abc"),
+            VariantPathElement::field("def"),
+        ]);
+        assert_eq!(path, expected);
+
+        // a number quoted with `'` is treated as field, not index
+        let path = VariantPath::try_from("foo['0'].bar[\"1\"]").unwrap();
+        let expected = VariantPath::from_iter([
+            VariantPathElement::field("foo"),
+            VariantPathElement::field("0"),
+            VariantPathElement::field("bar"),
+            VariantPathElement::field("1"),
         ]);
         assert_eq!(path, expected);
     }
@@ -321,5 +333,18 @@ mod tests {
         // No '[' before ']'
         let err = VariantPath::try_from("foo.bar]baz").unwrap_err();
         assert_eq!(err.to_string(), "Parser error: Unexpected ']' at byte 7");
+
+        // Invalid number(without quote) parse
+        let err = VariantPath::try_from("foo.bar[123abc]").unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Parser error: Invalid token in bracket request: `123abc`. Expected a quoted string or a number(e.g., `['field']` or `[123]`)"
+        );
+
+        let err = VariantPath::try_from("foo.bar[abc]").unwrap_err();
+        assert_eq!(
+            err.to_string(),
+            "Parser error: Invalid token in bracket request: `abc`. Expected a quoted string or a number(e.g., `['field']` or `[123]`)"
+        );
     }
 }

parquet-variant/src/utils.rs

@@ -170,9 +170,10 @@ pub(crate) fn fits_precision<const N: u32>(n: impl Into<i64>) -> bool {
 /// - `"foo"` -> single field `foo`
 /// - `"foo.bar"` -> nested fields `foo`, `bar`
 /// - `"[1]"` -> array index 1
+/// - `"['1']"` or `"["1"]"`-> field `1`
 /// - `"foo[1].bar"` -> field `foo`, index 1, field `bar`
-/// - `"[a.b]"` -> field `a.b` (dot is literal inside bracket)
-/// - `"[a\\]b]"` -> field `a]b` (escaped `]`
+/// - `"['a.b']"` -> field `a.b` (dot is literal inside bracket)
+/// - `"['a\]b']"` -> field `a]b` (escaped `]`
 /// - etc.
 ///
 /// # Errors
@@ -267,9 +268,23 @@ fn parse_in_bracket(s: &str, i: usize) -> Result<(VariantPathElement<'_>, usize)
         }
     };
 
-    let element = match unescaped.parse() {
-        Ok(idx) => VariantPathElement::index(idx),
-        Err(_) => VariantPathElement::field(unescaped),
+    let element = if let Some(inner) = unescaped
+        .strip_prefix('\'')
+        .and_then(|s| s.strip_suffix('\''))
+        .or_else(|| {
+            unescaped
+                .strip_prefix('"')
+                .and_then(|s| s.strip_suffix('"'))
+        }) {
+        // Quoted field name, e.g., ['field'] or ['123'] or ["123"]
+        VariantPathElement::field(inner.to_string())
+    } else {
+        let Ok(idx) = unescaped.parse() else {
+            return Err(ArrowError::ParseError(format!(
+                "Invalid token in bracket request: `{unescaped}`. Expected a quoted string or a number(e.g., `['field']` or `[123]`)"
+            )));
+        };
+        VariantPathElement::index(idx)
     };
 
     Ok((element, end + 1))