From a4d7f4cad88472dbcf5b4dd433cfef5f9624d7e8 Mon Sep 17 00:00:00 2001
From: Matthias Schiffer <mschiffer@universe-factory.net>
Date: Thu, 4 Apr 2024 20:04:30 +0200
Subject: driver: resolve: limit number of reported errors

Reporting all dependency cycles may lead to a large number of errors in
some cases, resulting in a long wait just for collecting the error data.
---
 crates/driver/src/resolve.rs | 59 ++++++++++++++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 18 deletions(-)

diff --git a/crates/driver/src/resolve.rs b/crates/driver/src/resolve.rs
index d03f26d..c13fcd2 100644
--- a/crates/driver/src/resolve.rs
+++ b/crates/driver/src/resolve.rs
@@ -7,7 +7,7 @@ use common::types::TaskID;
 use crate::args::TaskArgs;
 use crate::context::{self, Context, OutputRef, TaskRef};
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct DepChain<'ctx>(pub Vec<TaskRef<'ctx>>);
 
 impl<'ctx> fmt::Display for DepChain<'ctx> {
@@ -48,11 +48,14 @@ impl<'ctx> From<&'ctx TaskID> for DepChain<'ctx> {
 	}
 }
 
+const MAX_ERRORS: usize = 100;
+
 #[derive(Debug)]
 pub enum ErrorKind<'ctx> {
 	Context(context::Error<'ctx>),
 	OutputNotFound(&'ctx str),
 	DependencyCycle,
+	TooManyErrors,
 }
 
 #[derive(Debug)]
@@ -76,6 +79,13 @@ impl<'ctx> Error<'ctx> {
 		}
 	}
 
+	fn too_many_errors() -> Self {
+		Error {
+			dep_chain: DepChain::default(),
+			kind: ErrorKind::TooManyErrors,
+		}
+	}
+
 	fn extend(&mut self, task: &TaskRef<'ctx>) {
 		self.dep_chain.0.push(task.clone());
 	}
@@ -94,6 +104,9 @@ impl<'ctx> fmt::Display for Error<'ctx> {
 			ErrorKind::DependencyCycle => {
 				write!(f, "Dependency Cycle: ")?;
 			}
+			ErrorKind::TooManyErrors => {
+				write!(f, "Too many errors, stopping.")?;
+			}
 		}
 		dep_chain.fmt(f)
 	}
@@ -254,33 +267,43 @@ impl<'ctx> Resolver<'ctx> {
 			.insert(task.clone(), ResolveState::Resolving);
 
 		let mut ret = Vec::new();
-		let mut handle_errors = |errors: Vec<Error<'ctx>>| {
+		let mut handle_errors = |errors: Vec<Error<'ctx>>| -> Result<(), ()> {
 			for mut error in errors {
 				error.extend(task);
 				ret.push(error);
+
+				if ret.len() > MAX_ERRORS {
+					ret.push(Error::too_many_errors());
+					return Err(());
+				}
 			}
+			Ok(())
 		};
 
-		match self.ctx.get_inherit_depend(task) {
-			Ok(Some(inherit)) => {
-				handle_errors(self.add_task(&inherit, None));
-			}
-			Ok(None) => {}
-			Err(err) => {
-				handle_errors(vec![err.into()]);
+		let _ = (|| -> Result<(), ()> {
+			match self.ctx.get_inherit_depend(task) {
+				Ok(Some(inherit)) => {
+					handle_errors(self.add_task(&inherit, None))?;
+				}
+				Ok(None) => {}
+				Err(err) => {
+					handle_errors(vec![err.into()])?;
+				}
 			}
-		}
 
-		match get_dependent_outputs(self.ctx, task) {
-			Ok(rdeps) => {
-				for rdep in rdeps {
-					handle_errors(self.add_task(&rdep.task, Some(rdep.output)));
+			match get_dependent_outputs(self.ctx, task) {
+				Ok(rdeps) => {
+					for rdep in rdeps {
+						handle_errors(self.add_task(&rdep.task, Some(rdep.output)))?;
+					}
+				}
+				Err(errors) => {
+					handle_errors(errors)?;
 				}
 			}
-			Err(errors) => {
-				handle_errors(errors);
-			}
-		}
+
+			Ok(())
+		})();
 
 		if ret.is_empty() {
 			*self
-- 
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