driver: parse: replace nom with peg

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

4 files changed, 76 insertions, 95 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 05d10af..605a95b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -360,12 +360,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c8640c5d730cb13ebd907d8d04b52f55ac9a2eec55b440c8892f40d56c76c1d"
 
 [[package]]
-name = "minimal-lexical"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
-
-[[package]]
 name = "nix"
 version = "0.28.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -378,16 +372,6 @@ dependencies = [
 ]
 
 [[package]]
-name = "nom"
-version = "7.1.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d273983c5a657a70a3e8f2a01329822f3b8c8172b73826411a55751e404a0a4a"
-dependencies = [
- "memchr",
- "minimal-lexical",
-]
-
-[[package]]
 name = "olpc-cjson"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -405,6 +389,33 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
 [[package]]
+name = "peg"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "400bcab7d219c38abf8bd7cc2054eb9bbbd4312d66f6a5557d572a203f646f61"
+dependencies = [
+ "peg-macros",
+ "peg-runtime",
+]
+
+[[package]]
+name = "peg-macros"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "46e61cce859b76d19090f62da50a9fe92bab7c2a5f09e183763559a2ac392c90"
+dependencies = [
+ "peg-runtime",
+ "proc-macro2",
+ "quote",
+]
+
+[[package]]
+name = "peg-runtime"
+version = "0.8.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "36bae92c60fa2398ce4678b98b2c4b5a7c61099961ca1fa305aec04a9ad28922"
+
+[[package]]
 name = "pest"
 version = "2.7.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -478,7 +489,7 @@ dependencies = [
  "indoc",
  "lazy_static",
  "nix",
- "nom",
+ "peg",
  "rebel-common",
  "rebel-runner",
  "scoped-tls-hkt",
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::*;