From c58a3541e38fc601d1481041364c014f342eefa6 Mon Sep 17 00:00:00 2001
From: Tim de Jager <tdejager89@gmail.com>
Date: Wed, 8 Oct 2025 20:00:41 +0200
Subject: [PATCH 1/3] fix: normalize extra names in optional dependencies

---
 src/resolution.rs | 55 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/src/resolution.rs b/src/resolution.rs
index 9cc665f..c90996d 100644
--- a/src/resolution.rs
+++ b/src/resolution.rs
@@ -1,9 +1,17 @@
 use crate::{DependencyGroupSpecifier, DependencyGroups, ResolvedDependencies};
 use indexmap::IndexMap;
-use pep508_rs::Requirement;
+use pep508_rs::{ExtraName, Requirement};
 use std::fmt::Display;
+use std::str::FromStr;
 use thiserror::Error;
 
+/// Normalize a group/extra name according to PEP 685.
+fn normalize_name(name: &str) -> String {
+    ExtraName::from_str(name)
+        .map(|extra| extra.to_string())
+        .unwrap_or_else(|_| name.to_string())
+}
+
 #[derive(Debug, Error)]
 #[error(transparent)]
 pub struct ResolveError(#[from] ResolveErrorKind);
@@ -105,7 +113,16 @@ fn resolve_optional_dependency(
         return Ok(requirements.clone());
     }
 
-    let Some(unresolved_requirements) = optional_dependencies.get(extra) else {
+    // Normalize the extra name for lookup according to PEP 685
+    let normalized_extra = normalize_name(extra);
+
+    // Find the key in optional_dependencies by comparing normalized versions
+    let unresolved_requirements = optional_dependencies
+        .iter()
+        .find(|(key, _)| normalize_name(key) == normalized_extra)
+        .map(|(_, reqs)| reqs);
+
+    let Some(unresolved_requirements) = unresolved_requirements else {
         let parent = parents
             .iter()
             .last()
@@ -460,4 +477,38 @@ mod tests {
             vec![Requirement::from_str("numpy").unwrap()]
         );
     }
+
+    #[test]
+    fn optional_dependencies_with_underscores() {
+        // Test that optional dependency group names with underscores are normalized
+        // when referenced in extras. PEP 685 specifies that extras should be normalized
+        // by replacing _, ., - with a single -.
+        let source = r#"
+            [project]
+            name = "foo"
+
+            [project.optional-dependencies]
+            all = [
+              "foo[group-one]",
+              "foo[group_two]",
+            ]
+            group-one = [
+              "anyio>=4.9.0",
+            ]
+            group_two = [
+              "trio>=0.31.0",
+            ]
+        "#;
+        let pyproject_toml = PyProjectToml::new(source).unwrap();
+        let resolved_dependencies = pyproject_toml.resolve().unwrap();
+
+        // Both group-one and group_two should resolve correctly
+        assert_eq!(
+            resolved_dependencies.optional_dependencies["all"],
+            vec![
+                Requirement::from_str("anyio>=4.9.0").unwrap(),
+                Requirement::from_str("trio>=0.31.0").unwrap(),
+            ]
+        );
+    }
 }

From 8b90979bf7732a8b99024203395a394c18d42e4d Mon Sep 17 00:00:00 2001
From: Tim de Jager <tdejager89@gmail.com>
Date: Wed, 8 Oct 2025 20:04:36 +0200
Subject: [PATCH 2/3] fix: some comments

---
 src/resolution.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/resolution.rs b/src/resolution.rs
index c90996d..122e084 100644
--- a/src/resolution.rs
+++ b/src/resolution.rs
@@ -113,10 +113,10 @@ fn resolve_optional_dependency(
         return Ok(requirements.clone());
     }
 
-    // Normalize the extra name for lookup according to PEP 685
     let normalized_extra = normalize_name(extra);
 
     // Find the key in optional_dependencies by comparing normalized versions
+    // TODO: next breaking release remove this once Extra is added
     let unresolved_requirements = optional_dependencies
         .iter()
         .find(|(key, _)| normalize_name(key) == normalized_extra)

From 8c75b27d2aba26054f6d2d7811de9c07c40abdb4 Mon Sep 17 00:00:00 2001
From: Tim de Jager <tdejager89@gmail.com>
Date: Thu, 9 Oct 2025 11:28:45 +0200
Subject: [PATCH 3/3] fix: change test a bit

---
 src/resolution.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/resolution.rs b/src/resolution.rs
index 122e084..f7507ec 100644
--- a/src/resolution.rs
+++ b/src/resolution.rs
@@ -492,10 +492,10 @@ mod tests {
               "foo[group-one]",
               "foo[group_two]",
             ]
-            group-one = [
+            group_one = [
               "anyio>=4.9.0",
             ]
-            group_two = [
+            group-two = [
               "trio>=0.31.0",
             ]
         "#;