Error when --group includes non-existent groups (#8394)

## Summary

Part of https://github.com/astral-sh/uv/pull/8272.

crates/uv-configuration/src/dev.rs

@@ -163,10 +163,12 @@ impl DevGroupsSpecification {
         (self.dev.is_none() || self.dev.as_ref().is_some_and(DevMode::prod)) && self.groups.prod()
     }
 
+    /// Returns the flag that was used to request development dependencies.
     pub fn dev_mode(&self) -> Option<&DevMode> {
         self.dev.as_ref()
     }
 
+    /// Returns the list of groups to include.
     pub fn groups(&self) -> &GroupsSpecification {
         &self.groups
     }

crates/uv-workspace/src/pyproject.rs

@@ -555,6 +555,11 @@ impl DependencyGroups {
         self.0.get(group)
     }
 
+    /// Returns `true` if the dependency group is in the list.
+    pub fn contains_key(&self, group: &GroupName) -> bool {
+        self.0.contains_key(group)
+    }
+
     /// Returns an iterator over the dependency groups.
     pub fn iter(&self) -> impl Iterator<Item = (&GroupName, &Vec<DependencyGroupSpecifier>)> {
         self.0.iter()

crates/uv/src/commands/project/export.rs

@@ -70,6 +70,20 @@ pub(crate) async fn export(
         VirtualProject::discover(project_dir, &DiscoveryOptions::default()).await?
     };
 
+    // Validate the requested dependency groups.
+    for group in dev.groups().iter() {
+        if !project
+            .pyproject_toml()
+            .dependency_groups
+            .as_ref()
+            .is_some_and(|groups| groups.contains_key(group))
+        {
+            return Err(anyhow::anyhow!(
+                "Group `{group}` is not defined in the project's `dependency-group` table"
+            ));
+        }
+    }
+
     let VirtualProject::Project(project) = project else {
         return Err(anyhow::anyhow!("Legacy non-project roots are not supported in `uv export`; add a `[project]` table to your `pyproject.toml` to enable exports"));
     };

crates/uv/src/commands/project/run.rs

@@ -469,6 +469,20 @@ pub(crate) async fn run(
                 );
             }
 
+            // Validate the requested dependency groups.
+            for group in dev.groups().iter() {
+                if !project
+                    .pyproject_toml()
+                    .dependency_groups
+                    .as_ref()
+                    .is_some_and(|groups| groups.contains_key(group))
+                {
+                    return Err(anyhow::anyhow!(
+                        "Group `{group}` is not defined in the project's `dependency-group` table"
+                    ));
+                }
+            }
+
             let venv = if isolated {
                 debug!("Creating isolated virtual environment");
 

crates/uv/src/commands/project/sync.rs

@@ -93,6 +93,20 @@ pub(crate) async fn sync(
         warn_user!("Skipping installation of entry points (`project.scripts`) because this project is not packaged; to install entry points, set `tool.uv.package = true` or define a `build-system`");
     }
 
+    // Validate the requested dependency groups.
+    for group in dev.groups().iter() {
+        if !project
+            .pyproject_toml()
+            .dependency_groups
+            .as_ref()
+            .is_some_and(|groups| groups.contains_key(group))
+        {
+            return Err(anyhow::anyhow!(
+                "Group `{group}` is not defined in the project's `dependency-group` table"
+            ));
+        }
+    }
+
     // Discover or create the virtual environment.
     let venv = project::get_or_init_environment(
         target.workspace(),

crates/uv/tests/it/sync.rs

@@ -1226,6 +1226,53 @@ fn sync_dev_group() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn sync_non_existent_group() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let pyproject_toml = context.temp_dir.child("pyproject.toml");
+    pyproject_toml.write_str(
+        r#"
+        [project]
+        name = "project"
+        version = "0.1.0"
+        requires-python = ">=3.12"
+        dependencies = ["typing-extensions"]
+
+        [dependency-groups]
+        foo = []
+        bar = ["requests"]
+        "#,
+    )?;
+
+    context.lock().assert().success();
+
+    // Requesting a non-existent group should fail.
+    uv_snapshot!(context.filters(), context.sync().arg("--group").arg("baz"), @r###"
+    success: false
+    exit_code: 2
+    ----- stdout -----
+
+    ----- stderr -----
+    error: Group `baz` is not defined in the project's `dependency-group` table
+    "###);
+
+    // Requesting an empty group should succeed.
+    uv_snapshot!(context.filters(), context.sync().arg("--group").arg("foo"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 7 packages in [TIME]
+    Prepared 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + typing-extensions==4.10.0
+    "###);
+
+    Ok(())
+}
+
 /// Regression test for <https://github.com/astral-sh/uv/issues/6316>.
 ///
 /// Previously, we would read metadata statically from pyproject.toml and write that to `uv.lock`. In