From f3bb1a265ee4663d0e459858328b18f8e534a07d Mon Sep 17 00:00:00 2001
From: rm-dr <96270320+rm-dr@users.noreply.github.com>
Date: Wed, 11 Mar 2026 12:54:02 -0700
Subject: [PATCH] Improve arg parsing

---
 crates/pile-config/src/objectpath/mod.rs      |   7 +-
 crates/pile-config/src/objectpath/parser.rs   | 204 +++++++++++++++---
 .../src/extract/item/epub/epub_meta.rs        |  10 +-
 .../src/extract/item/epub/epub_text.rs        |  10 +-
 .../pile-value/src/extract/item/epub/mod.rs   |  12 +-
 crates/pile-value/src/extract/item/exif.rs    |  10 +-
 crates/pile-value/src/extract/item/flac.rs    |  10 +-
 crates/pile-value/src/extract/item/fs.rs      |  10 +-
 crates/pile-value/src/extract/item/id3.rs     |  10 +-
 crates/pile-value/src/extract/item/mod.rs     |   8 +-
 crates/pile-value/src/extract/item/pdf/mod.rs |  14 +-
 .../src/extract/item/pdf/pdf_meta.rs          |   9 +-
 .../src/extract/item/pdf/pdf_text.rs          |  10 +-
 crates/pile-value/src/extract/item/sidecar.rs |   8 +-
 crates/pile-value/src/extract/item/toml.rs    |  10 +-
 crates/pile-value/src/extract/misc/map.rs     |  10 +-
 crates/pile-value/src/extract/string.rs       |  62 +++---
 crates/pile-value/src/extract/traits.rs       |   3 +-
 crates/pile-value/src/value/value.rs          |   8 +-
 19 files changed, 327 insertions(+), 98 deletions(-)

diff --git a/crates/pile-config/src/objectpath/mod.rs b/crates/pile-config/src/objectpath/mod.rs
index d3598b9..668518a 100644
--- a/crates/pile-config/src/objectpath/mod.rs
+++ b/crates/pile-config/src/objectpath/mod.rs
@@ -41,8 +41,11 @@ pub enum PathSegment {
 	/// Go to root node (`$` identifier)
 	Root,
 
-	/// Go to a child of the current object
-	Field(Label),
+	/// Go to a child of the current object.
+	Field {
+		name: Label,
+		args: Option<SmartString<LazyCompact>>,
+	},
 
 	/// Go to an element of the current list
 	Index(i64),
diff --git a/crates/pile-config/src/objectpath/parser.rs b/crates/pile-config/src/objectpath/parser.rs
index ea96acf..7b42fa2 100644
--- a/crates/pile-config/src/objectpath/parser.rs
+++ b/crates/pile-config/src/objectpath/parser.rs
@@ -1,10 +1,80 @@
 use std::str::FromStr;
 
+use smartstring::{LazyCompact, SmartString};
+
 use crate::{
 	Label,
 	objectpath::{PathParseError, PathSegment, tokenizer::Token},
 };
 
+/// Parse an ident token into a `PathSegment::Field`, handling optional args of
+/// the form `name(args)`.  Parens inside args may be nested; `\(` and `\)` are
+/// escaped and do not affect depth counting.
+fn parse_field(ident: &str, position: usize) -> Result<PathSegment, PathParseError> {
+	let bytes = ident.as_bytes();
+	let mut i = 0;
+
+	// Find the first unescaped '(' — everything before it is the name.
+	let open_paren: Option<usize> = loop {
+		if i >= bytes.len() {
+			break None;
+		}
+		match bytes[i] {
+			b'\\' => i += 2, // skip escaped character
+			b'(' => break Some(i),
+			_ => i += 1,
+		}
+	};
+
+	let name_str = &ident[..open_paren.unwrap_or(bytes.len())];
+	let name = Label::new(name_str).ok_or_else(|| PathParseError::InvalidField {
+		position,
+		str: name_str.into(),
+	})?;
+
+	let Some(open_pos) = open_paren else {
+		return Ok(PathSegment::Field { name, args: None });
+	};
+
+	// Scan args, tracking paren depth.
+	let args_start = open_pos + 1;
+	let mut depth: usize = 1;
+	let mut j = args_start;
+
+	while j < bytes.len() {
+		match bytes[j] {
+			b'\\' => j += 2, // skip escaped character
+			b'(' => {
+				depth += 1;
+				j += 1;
+			}
+			b')' => {
+				depth -= 1;
+				if depth == 0 {
+					// Closing paren must be the last character.
+					if j + 1 != bytes.len() {
+						return Err(PathParseError::Syntax {
+							position: position + j + 1,
+						});
+					}
+					let args: SmartString<LazyCompact> = ident[args_start..j].into();
+					return Ok(PathSegment::Field {
+						name,
+						args: Some(args),
+					});
+				}
+				j += 1;
+			}
+			_ => j += 1,
+		}
+	}
+
+	// Reached end of ident without finding the matching ')'.
+	Err(PathParseError::Syntax {
+		position: position + ident.len(),
+	})
+}
+
 enum State {
 	Start,
 
@@ -72,14 +142,7 @@ impl Parser {
 				// MARK: dot
 				//
 				(State::Dot, (p, Token::Ident(ident))) => {
-					self.segments
-						.push(PathSegment::Field(Label::new(*ident).ok_or_else(|| {
-							PathParseError::InvalidField {
-								position: *p,
-								str: (*ident).into(),
-							}
-						})?));
-
+					self.segments.push(parse_field(ident, *p)?);
 					self.state = State::Selected;
 				}
 
@@ -161,27 +224,30 @@ mod tests {
 		parse_test("$", Ok(&[PathSegment::Root]));
 	}
 
+	fn field(name: &str) -> PathSegment {
+		PathSegment::Field {
+			name: Label::new(name).unwrap(),
+			args: None,
+		}
+	}
+
+	fn field_args(name: &str, args: &str) -> PathSegment {
+		PathSegment::Field {
+			name: Label::new(name).unwrap(),
+			args: Some(args.into()),
+		}
+	}
+
 	#[test]
 	fn single_field() {
-		parse_test(
-			"$.foo",
-			Ok(&[
-				PathSegment::Root,
-				PathSegment::Field(Label::new("foo").unwrap()),
-			]),
-		);
+		parse_test("$.foo", Ok(&[PathSegment::Root, field("foo")]));
 	}
 
 	#[test]
 	fn nested_fields() {
 		parse_test(
 			"$.foo.bar.baz",
-			Ok(&[
-				PathSegment::Root,
-				PathSegment::Field(Label::new("foo").unwrap()),
-				PathSegment::Field(Label::new("bar").unwrap()),
-				PathSegment::Field(Label::new("baz").unwrap()),
-			]),
+			Ok(&[PathSegment::Root, field("foo"), field("bar"), field("baz")]),
 		);
 	}
 
@@ -189,11 +255,7 @@ mod tests {
 	fn array_index() {
 		parse_test(
 			"$.items[0]",
-			Ok(&[
-				PathSegment::Root,
-				PathSegment::Field(Label::new("items").unwrap()),
-				PathSegment::Index(0),
-			]),
+			Ok(&[PathSegment::Root, field("items"), PathSegment::Index(0)]),
 		);
 	}
 
@@ -203,7 +265,7 @@ mod tests {
 			"$.a[1][2]",
 			Ok(&[
 				PathSegment::Root,
-				PathSegment::Field(Label::new("a").unwrap()),
+				field("a"),
 				PathSegment::Index(1),
 				PathSegment::Index(2),
 			]),
@@ -216,9 +278,9 @@ mod tests {
 			"$.a[0].b",
 			Ok(&[
 				PathSegment::Root,
-				PathSegment::Field(Label::new("a").unwrap()),
+				field("a"),
 				PathSegment::Index(0),
-				PathSegment::Field(Label::new("b").unwrap()),
+				field("b"),
 			]),
 		);
 	}
@@ -227,14 +289,94 @@ mod tests {
 	fn negative_index() {
 		parse_test(
 			"$.a[-1]",
+			Ok(&[PathSegment::Root, field("a"), PathSegment::Index(-1)]),
+		);
+	}
+
+	// MARK: args
+
+	#[test]
+	fn field_with_simple_args() {
+		parse_test(
+			"$.foo(bar)",
+			Ok(&[PathSegment::Root, field_args("foo", "bar")]),
+		);
+	}
+
+	#[test]
+	fn field_with_empty_args() {
+		parse_test("$.foo()", Ok(&[PathSegment::Root, field_args("foo", "")]));
+	}
+
+	#[test]
+	fn field_with_nested_parens_in_args() {
+		parse_test(
+			"$.foo(a(b)c)",
+			Ok(&[PathSegment::Root, field_args("foo", "a(b)c")]),
+		);
+	}
+
+	#[test]
+	fn field_with_deeply_nested_parens_in_args() {
+		parse_test(
+			"$.foo(a(b(c))d)",
+			Ok(&[PathSegment::Root, field_args("foo", "a(b(c))d")]),
+		);
+	}
+
+	#[test]
+	fn field_with_escaped_open_paren_in_args() {
+		// "$.foo(a\(b)" — '\(' is escaped, so depth never rises above 1; ')' closes it
+		parse_test(
+			r"$.foo(a\(b)",
+			Ok(&[PathSegment::Root, field_args("foo", r"a\(b")]),
+		);
+	}
+
+	#[test]
+	fn field_with_escaped_close_paren_in_args() {
+		// "$.foo(a\)b)" — '\)' is escaped, the second ')' closes at depth 0
+		parse_test(
+			r"$.foo(a\)b)",
+			Ok(&[PathSegment::Root, field_args("foo", r"a\)b")]),
+		);
+	}
+
+	#[test]
+	fn field_with_both_escaped_parens_in_args() {
+		parse_test(
+			r"$.foo(a\(b\)c)",
+			Ok(&[PathSegment::Root, field_args("foo", r"a\(b\)c")]),
+		);
+	}
+
+	#[test]
+	fn field_args_with_multiple_segments() {
+		parse_test(
+			"$.foo(x).bar(y)",
 			Ok(&[
 				PathSegment::Root,
-				PathSegment::Field(Label::new("a").unwrap()),
-				PathSegment::Index(-1),
+				field_args("foo", "x"),
+				field_args("bar", "y"),
 			]),
 		);
 	}
 
+	#[test]
+	fn field_args_unclosed_paren_error() {
+		// Missing closing ')' → Syntax error at end of source
+		parse_test("$.foo(bar", Err(PathParseError::Syntax { position: 9 }));
+	}
+
+	#[test]
+	fn field_args_trailing_chars_after_close_error() {
+		// Closing ')' is not the last char → Syntax error at the trailing char
+		parse_test(
+			"$.foo(bar)baz",
+			Err(PathParseError::Syntax { position: 10 }),
+		);
+	}
+
 	#[test]
 	fn non_ascii_error() {
 		parse_test(
diff --git a/crates/pile-value/src/extract/item/epub/epub_meta.rs b/crates/pile-value/src/extract/item/epub/epub_meta.rs
index 31d2d47..d4e7622 100644
--- a/crates/pile-value/src/extract/item/epub/epub_meta.rs
+++ b/crates/pile-value/src/extract/item/epub/epub_meta.rs
@@ -85,7 +85,15 @@ impl EpubMetaExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for EpubMetaExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/epub/epub_text.rs b/crates/pile-value/src/extract/item/epub/epub_text.rs
index e04b83c..2d8f645 100644
--- a/crates/pile-value/src/extract/item/epub/epub_text.rs
+++ b/crates/pile-value/src/extract/item/epub/epub_text.rs
@@ -95,7 +95,15 @@ fn strip_html(html: &str) -> String {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for EpubTextExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/epub/mod.rs b/crates/pile-value/src/extract/item/epub/mod.rs
index f742dc0..199deda 100644
--- a/crates/pile-value/src/extract/item/epub/mod.rs
+++ b/crates/pile-value/src/extract/item/epub/mod.rs
@@ -28,10 +28,14 @@ impl EpubExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for EpubExtractor {
-	async fn field(&self, name: &pile_config::Label) -> Result<Option<PileValue>, std::io::Error> {
-		match name.as_str() {
-			"text" => self.text.field(name).await,
-			"meta" => Ok(Some(PileValue::ObjectExtractor(self.meta.clone()))),
+	async fn field(
+		&self,
+		name: &pile_config::Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		match (name.as_str(), args) {
+			("text", args) => self.text.field(name, args).await,
+			("meta", None) => Ok(Some(PileValue::ObjectExtractor(self.meta.clone()))),
 			_ => Ok(None),
 		}
 	}
diff --git a/crates/pile-value/src/extract/item/exif.rs b/crates/pile-value/src/extract/item/exif.rs
index 56a5f8d..abf7be2 100644
--- a/crates/pile-value/src/extract/item/exif.rs
+++ b/crates/pile-value/src/extract/item/exif.rs
@@ -86,7 +86,15 @@ fn tag_to_label(tag: &str) -> Option<Label> {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for ExifExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/flac.rs b/crates/pile-value/src/extract/item/flac.rs
index 4d00a88..027d2be 100644
--- a/crates/pile-value/src/extract/item/flac.rs
+++ b/crates/pile-value/src/extract/item/flac.rs
@@ -142,7 +142,15 @@ impl FlacExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for FlacExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		if name.as_str() == "images"
 			&& let Some(ref images) = self.images
 		{
diff --git a/crates/pile-value/src/extract/item/fs.rs b/crates/pile-value/src/extract/item/fs.rs
index a1cbe40..ba5f0f5 100644
--- a/crates/pile-value/src/extract/item/fs.rs
+++ b/crates/pile-value/src/extract/item/fs.rs
@@ -70,7 +70,15 @@ impl FsExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for FsExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner()?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/id3.rs b/crates/pile-value/src/extract/item/id3.rs
index 8b787de..39835a5 100644
--- a/crates/pile-value/src/extract/item/id3.rs
+++ b/crates/pile-value/src/extract/item/id3.rs
@@ -123,7 +123,15 @@ fn frame_id_to_field(id: &str) -> Cow<'static, str> {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for Id3Extractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/mod.rs b/crates/pile-value/src/extract/item/mod.rs
index 0bea6f1..19da047 100644
--- a/crates/pile-value/src/extract/item/mod.rs
+++ b/crates/pile-value/src/extract/item/mod.rs
@@ -80,8 +80,12 @@ impl ItemExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for ItemExtractor {
-	async fn field(&self, name: &pile_config::Label) -> Result<Option<PileValue>, std::io::Error> {
-		self.inner.field(name).await
+	async fn field(
+		&self,
+		name: &pile_config::Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		self.inner.field(name, args).await
 	}
 
 	#[expect(clippy::unwrap_used)]
diff --git a/crates/pile-value/src/extract/item/pdf/mod.rs b/crates/pile-value/src/extract/item/pdf/mod.rs
index 2a5f6e3..322e892 100644
--- a/crates/pile-value/src/extract/item/pdf/mod.rs
+++ b/crates/pile-value/src/extract/item/pdf/mod.rs
@@ -37,12 +37,16 @@ impl PdfExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for PdfExtractor {
-	async fn field(&self, name: &pile_config::Label) -> Result<Option<PileValue>, std::io::Error> {
-		match name.as_str() {
-			"text" => self.text.field(name).await,
-			"meta" => Ok(Some(PileValue::ObjectExtractor(self.meta.clone()))),
+	async fn field(
+		&self,
+		name: &pile_config::Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		match (name.as_str(), args) {
+			("text", args) => self.text.field(name, args).await,
+			("meta", None) => Ok(Some(PileValue::ObjectExtractor(self.meta.clone()))),
 			#[cfg(feature = "pdfium")]
-			"pages" => Ok(Some(PileValue::ListExtractor(self.pages.clone()))),
+			("pages", None) => Ok(Some(PileValue::ListExtractor(self.pages.clone()))),
 			_ => Ok(None),
 		}
 	}
diff --git a/crates/pile-value/src/extract/item/pdf/pdf_meta.rs b/crates/pile-value/src/extract/item/pdf/pdf_meta.rs
index 9c07599..1c7e217 100644
--- a/crates/pile-value/src/extract/item/pdf/pdf_meta.rs
+++ b/crates/pile-value/src/extract/item/pdf/pdf_meta.rs
@@ -122,7 +122,14 @@ fn format_date(d: &Date) -> String {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for PdfMetaExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/pdf/pdf_text.rs b/crates/pile-value/src/extract/item/pdf/pdf_text.rs
index f8130e7..5b979f3 100644
--- a/crates/pile-value/src/extract/item/pdf/pdf_text.rs
+++ b/crates/pile-value/src/extract/item/pdf/pdf_text.rs
@@ -102,7 +102,15 @@ impl PdfTextExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for PdfTextExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/item/sidecar.rs b/crates/pile-value/src/extract/item/sidecar.rs
index be80951..5db73a2 100644
--- a/crates/pile-value/src/extract/item/sidecar.rs
+++ b/crates/pile-value/src/extract/item/sidecar.rs
@@ -23,12 +23,16 @@ impl SidecarExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for SidecarExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
 		match self
 			.output
 			.get_or_init(|| self.item.sidecar().map(TomlExtractor::new))
 		{
-			Some(x) => Ok(x.field(name).await?),
+			Some(x) => Ok(x.field(name, args).await?),
 			None => Ok(Some(PileValue::Null)),
 		}
 	}
diff --git a/crates/pile-value/src/extract/item/toml.rs b/crates/pile-value/src/extract/item/toml.rs
index 91056ff..65ddcb7 100644
--- a/crates/pile-value/src/extract/item/toml.rs
+++ b/crates/pile-value/src/extract/item/toml.rs
@@ -68,7 +68,15 @@ impl TomlExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for TomlExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.get_inner().await?.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/misc/map.rs b/crates/pile-value/src/extract/misc/map.rs
index 8005678..4abbfca 100644
--- a/crates/pile-value/src/extract/misc/map.rs
+++ b/crates/pile-value/src/extract/misc/map.rs
@@ -10,7 +10,15 @@ pub struct MapExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for MapExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		if args.is_some() {
+			return Ok(None);
+		}
+
 		Ok(self.inner.get(name).cloned())
 	}
 
diff --git a/crates/pile-value/src/extract/string.rs b/crates/pile-value/src/extract/string.rs
index 4f4e144..9cf281b 100644
--- a/crates/pile-value/src/extract/string.rs
+++ b/crates/pile-value/src/extract/string.rs
@@ -4,20 +4,6 @@ use std::sync::Arc;
 
 use crate::{extract::traits::ObjectExtractor, value::PileValue};
 
-fn parse_name(s: &str) -> (&str, Option<&str>) {
-	match s.find('(') {
-		None => (s, None),
-		Some(i) => {
-			let name = &s[..i];
-			let rest = &s[i + 1..];
-			match rest.strip_suffix(')') {
-				Some(args) => (name, Some(args)),
-				None => (name, None),
-			}
-		}
-	}
-}
-
 pub struct StringExtractor {
 	item: Arc<SmartString<LazyCompact>>,
 }
@@ -30,9 +16,12 @@ impl StringExtractor {
 
 #[async_trait::async_trait]
 impl ObjectExtractor for StringExtractor {
-	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
-		let (name, args) = parse_name(name.as_str());
-		Ok(match (name, args) {
+	async fn field(
+		&self,
+		name: &Label,
+		args: Option<&str>,
+	) -> Result<Option<PileValue>, std::io::Error> {
+		Ok(match (name.as_str(), args) {
 			("trim", None) => Some(PileValue::String(Arc::new(
 				self.item.as_str().trim().into(),
 			))),
@@ -98,8 +87,8 @@ mod tests {
 	}
 
 	#[expect(clippy::unwrap_used)]
-	async fn field(ext: &StringExtractor, name: &str) -> Option<PileValue> {
-		ext.field(&Label::new(name).unwrap()).await.unwrap()
+	async fn field(ext: &StringExtractor, name: &str, args: Option<&str>) -> Option<PileValue> {
+		ext.field(&Label::new(name).unwrap(), args).await.unwrap()
 	}
 
 	fn string(v: Option<PileValue>) -> Option<String> {
@@ -125,20 +114,20 @@ mod tests {
 	#[tokio::test]
 	async fn trim() {
 		assert_eq!(
-			string(field(&extractor("  hi  "), "trim").await),
+			string(field(&extractor("  hi  "), "trim", None).await),
 			Some("hi".into())
 		);
 	}
 
 	#[tokio::test]
 	async fn trim_no_args() {
-		assert!(field(&extractor("x"), "trim(foo)").await.is_none());
+		assert!(field(&extractor("x"), "trim", Some("foo")).await.is_none());
 	}
 
 	#[tokio::test]
 	async fn nonempty_with_content() {
 		assert!(matches!(
-			field(&extractor("hello"), "nonempty").await,
+			field(&extractor("hello"), "nonempty", None).await,
 			Some(PileValue::String(_))
 		));
 	}
@@ -146,7 +135,7 @@ mod tests {
 	#[tokio::test]
 	async fn nonempty_empty_string() {
 		assert!(matches!(
-			field(&extractor(""), "nonempty").await,
+			field(&extractor(""), "nonempty", None).await,
 			Some(PileValue::Null)
 		));
 	}
@@ -154,7 +143,7 @@ mod tests {
 	#[tokio::test]
 	async fn trimprefix_present() {
 		assert_eq!(
-			string(field(&extractor("foobar"), "trimprefix(foo)").await),
+			string(field(&extractor("foobar"), "trimprefix", Some("foo")).await),
 			Some("bar".into())
 		);
 	}
@@ -162,20 +151,24 @@ mod tests {
 	#[tokio::test]
 	async fn trimprefix_absent() {
 		assert_eq!(
-			string(field(&extractor("foobar"), "trimprefix(baz)").await),
+			string(field(&extractor("foobar"), "trimprefix", Some("baz")).await),
 			Some("foobar".into())
 		);
 	}
 
 	#[tokio::test]
 	async fn trimprefix_no_args() {
-		assert!(field(&extractor("foobar"), "trimprefix").await.is_none());
+		assert!(
+			field(&extractor("foobar"), "trimprefix", None)
+				.await
+				.is_none()
+		);
 	}
 
 	#[tokio::test]
 	async fn trimsuffix_present() {
 		assert_eq!(
-			string(field(&extractor("foobar"), "trimsuffix(bar)").await),
+			string(field(&extractor("foobar"), "trimsuffix", Some("bar")).await),
 			Some("foo".into())
 		);
 	}
@@ -183,7 +176,7 @@ mod tests {
 	#[tokio::test]
 	async fn trimsuffix_absent() {
 		assert_eq!(
-			string(field(&extractor("foobar"), "trimsuffix(baz)").await),
+			string(field(&extractor("foobar"), "trimsuffix", Some("baz")).await),
 			Some("foobar".into())
 		);
 	}
@@ -191,7 +184,7 @@ mod tests {
 	#[tokio::test]
 	async fn split_basic() {
 		assert_eq!(
-			array(field(&extractor("a,b,c"), "split(,)").await),
+			array(field(&extractor("a,b,c"), "split", Some(",")).await),
 			vec!["a", "b", "c"]
 		);
 	}
@@ -199,23 +192,18 @@ mod tests {
 	#[tokio::test]
 	async fn split_no_match() {
 		assert_eq!(
-			array(field(&extractor("abc"), "split(,)").await),
+			array(field(&extractor("abc"), "split", Some(",")).await),
 			vec!["abc"]
 		);
 	}
 
 	#[tokio::test]
 	async fn split_no_args() {
-		assert!(field(&extractor("abc"), "split").await.is_none());
-	}
-
-	#[tokio::test]
-	async fn split_unclosed_paren() {
-		assert!(field(&extractor("abc"), "split(,").await.is_none());
+		assert!(field(&extractor("abc"), "split", None).await.is_none());
 	}
 
 	#[tokio::test]
 	async fn unknown_field() {
-		assert!(field(&extractor("abc"), "bogus").await.is_none());
+		assert!(field(&extractor("abc"), "bogus", None).await.is_none());
 	}
 }
diff --git a/crates/pile-value/src/extract/traits.rs b/crates/pile-value/src/extract/traits.rs
index 4ca0f17..b81a1aa 100644
--- a/crates/pile-value/src/extract/traits.rs
+++ b/crates/pile-value/src/extract/traits.rs
@@ -10,6 +10,7 @@ pub trait ObjectExtractor: Send + Sync {
 	async fn field(
 		&self,
 		name: &pile_config::Label,
+		args: Option<&str>,
 	) -> Result<Option<crate::value::PileValue>, std::io::Error>;
 
 	/// Return all fields in this extractor.
@@ -22,7 +23,7 @@ pub trait ObjectExtractor: Send + Sync {
 		let keys = self.fields().await?;
 		let mut map = serde_json::Map::new();
 		for k in &keys {
-			let v = match self.field(k).await? {
+			let v = match self.field(k, None).await? {
 				Some(x) => x,
 				None => continue,
 			};
diff --git a/crates/pile-value/src/value/value.rs b/crates/pile-value/src/value/value.rs
index 56525ac..350800d 100644
--- a/crates/pile-value/src/value/value.rs
+++ b/crates/pile-value/src/value/value.rs
@@ -97,7 +97,7 @@ impl PileValue {
 		for s in &query.segments {
 			match s {
 				PathSegment::Root => out = Some(self.clone()),
-				PathSegment::Field(field) => {
+				PathSegment::Field { name, args } => {
 					let e = match out.map(|x| x.object_extractor()) {
 						Some(e) => e,
 						None => {
@@ -106,7 +106,7 @@ impl PileValue {
 						}
 					};
 
-					out = e.field(field).await?;
+					out = e.field(name, args.as_deref()).await?;
 				}
 
 				PathSegment::Index(idx) => {
@@ -163,7 +163,7 @@ impl PileValue {
 				let keys = e.fields().await?;
 				let mut map = Map::new();
 				for k in &keys {
-					let v = match e.field(k).await? {
+					let v = match e.field(k, None).await? {
 						Some(x) => x,
 						None => continue,
 					};
@@ -216,7 +216,7 @@ impl PileValue {
 				let keys = e.fields().await?;
 				let mut map = Map::new();
 				for k in &keys {
-					let v = match e.field(k).await? {
+					let v = match e.field(k, None).await? {
 						Some(x) => x,
 						None => continue,
 					};