driver: parse: replace nom with peg

The PEG-based parser is much more concise and easier to understand than
the old combinator solution.

3 files changed, 48 insertions, 78 deletions

diff --git a/crates/driver/Cargo.toml b/crates/driver/Cargo.toml
index 683ebbe..673e0ba 100644
--- a/crates/driver/Cargo.toml
+++ b/crates/driver/Cargo.toml
@@ -18,8 +18,8 @@ handlebars = "5.1.2"
 indoc = "2.0.4"
 lazy_static = "1.4.0"
 nix = { version = "0.28.0", features = ["poll"] }
-nom = "7.1.0"
 scoped-tls-hkt = "0.1.2"
 serde = { version = "1", features = ["derive", "rc"] }
 serde_yaml = "0.9"
 walkdir = "2"
+peg = "0.8.2"
diff --git a/crates/driver/src/context.rs b/crates/driver/src/context.rs
index 47259b3..4698171 100644
--- a/crates/driver/src/context.rs
+++ b/crates/driver/src/context.rs
@@ -355,7 +355,9 @@ impl Context {
 	}
 
 	pub fn parse(&self, s: &str) -> error::Result<(TaskRef, TaskFlags)> {
-		let (parsed, flags) = parse::parse_task_with_flags(s).context("Invalid task syntax")?;
+		let (parsed, flags) = parse::task_with_flags(s)
+			.ok()
+			.context("Invalid task syntax")?;
 
 		let recipe = parsed.id.recipe.to_string();
 		let task = parsed.id.task.to_string();
diff --git a/crates/driver/src/parse.rs b/crates/driver/src/parse.rs
index df540fc..f71fd18 100644
--- a/crates/driver/src/parse.rs
+++ b/crates/driver/src/parse.rs
@@ -1,10 +1,3 @@
-use nom::{
-	bytes::complete::{tag, take_while1},
-	combinator::{all_consuming, opt},
-	error::ParseError,
-	Err, IResult, InputLength, Parser,
-};
-
 #[derive(Debug, Clone, Copy)]
 pub struct TaskID<'a> {
 	pub recipe: &'a str,
@@ -28,74 +21,49 @@ pub struct TaskFlags {
 	pub force_run: bool,
 }
 
-fn is_name_char(c: char) -> bool {
-	matches!(c, 'a'..='z' | 'A' ..='Z' | '0'..='9' | '_' | '-')
-}
-
-fn name(input: &str) -> IResult<&str, &str> {
-	take_while1(is_name_char)(input)
-}
-
-fn task_id(input: &str) -> IResult<&str, TaskID> {
-	let (input, recipe) = name(input)?;
-	let (input, _) = tag(":")(input)?;
-	let (input, task) = name(input)?;
-	Ok((input, TaskID { recipe, task }))
-}
-
-fn task_arg_target(input: &str) -> IResult<&str, &str> {
-	let (input, _) = tag(":")(input)?;
-	let (input, target) = name(input)?;
-	Ok((input, target))
-}
-
-fn task_args(input: &str) -> IResult<&str, TaskArgs> {
-	let (input, _) = tag("/")(input)?;
-	let (input, host) = opt(name)(input)?;
-	let (input, target) = opt(task_arg_target)(input)?;
-
-	Ok((input, TaskArgs { host, target }))
-}
-
-fn task(input: &str) -> IResult<&str, Task> {
-	let (input, id) = task_id(input)?;
-	let (input, args) = opt(task_args)(input)?;
-
-	Ok((
-		input,
-		Task {
-			id,
-			args: args.unwrap_or_default(),
-		},
-	))
-}
-
-fn task_flags(input: &str) -> IResult<&str, TaskFlags> {
-	let (input, force_run) = opt(tag("+"))(input)?;
-
-	Ok((
-		input,
-		TaskFlags {
-			force_run: force_run.is_some(),
-		},
-	))
+peg::parser! {
+	grammar rules() for str {
+		rule t<T>(tag: rule<()>, value: rule<T>) -> T
+			= tag() v:value() { v }
+
+		rule name_char()
+			= ['a'..='z' | 'A' ..='Z' | '0'..='9' | '_' | '-']
+
+		rule name() -> &'input str
+			= $(name_char()+)
+
+		rule task_id() -> TaskID<'input>
+			= recipe:name() ":" task:name() {
+				TaskID { recipe, task }
+			}
+
+		rule task_args() -> TaskArgs<'input>
+			= "/" host:name()? target:t(<":">, <name()>)? {
+				TaskArgs {
+					host,
+					target,
+				}
+			}
+			/ { Default::default() }
+
+		pub rule task() -> Task<'input>
+			= id:task_id() args:task_args() {
+				Task {
+					id,
+					args,
+				}
+			}
+
+		rule force_run() -> bool
+			= "+" { true }
+			/ { false }
+
+		rule task_flags() -> TaskFlags
+			= force_run:force_run() { TaskFlags { force_run } }
+
+		pub rule task_with_flags() -> (Task<'input>, TaskFlags)
+			= task:task() flags:task_flags() { (task, flags) }
+	}
 }
 
-fn task_with_flags(input: &str) -> IResult<&str, (Task, TaskFlags)> {
-	let (input, task) = task(input)?;
-	let (input, flags) = task_flags(input)?;
-
-	Ok((input, (task, flags)))
-}
-
-fn parse_all<I, O, E: ParseError<I>, F>(f: F, input: I) -> Result<O, Err<E>>
-where
-	I: InputLength,
-	F: Parser<I, O, E>,
-{
-	all_consuming(f)(input).map(|(_, result)| result)
-}
-
-pub fn parse_task_with_flags(input: &str) -> Option<(Task, TaskFlags)> {
-	parse_all(task_with_flags, input).ok()
-}
+pub use rules::*;