feat(labeler): add /assign and /unassign support

.github/actions/labeler-action/action.yml

@@ -20,6 +20,9 @@ inputs:
   changed_files:
     description: "comma separated list of files"
     required: false
+  comment_author:
+    description: "GitHub login of the comment author; used as the implicit target of bare /assign and /unassign."
+    required: false
 
 runs:
   using: "docker"
@@ -31,3 +34,4 @@ runs:
     - "${{ inputs.issue_number }}"
     - "${{ inputs.comment_body }}"
     - "${{ inputs.changed_files }}"
+    - "${{ inputs.comment_author }}"

utilities/labeler/README.md

@@ -64,6 +64,38 @@ Apply labels based on changed file paths:
     match: "label-pattern"  # Supports wildcards like "triage/*"
 ```
 
+### Assign / Unassign
+Add or remove issue/PR assignees from a slash command. The command arguments are
+treated as GitHub logins (a leading `@` is optional). With no arguments, the comment
+author is used, so a bare `/assign` self-assigns — this requires the `comment_author`
+input (CLI: the optional trailing `comment_author` argument) to be set.
+```yaml
+- name: assign
+  kind: match
+  spec:
+    command: "/assign"
+  actions:
+  - kind: assign
+
+- name: unassign
+  kind: match
+  spec:
+    command: "/unassign"
+  actions:
+  - kind: unassign
+```
+
+Example comments:
+```
+/assign                 # assigns the comment author
+/assign @alice bob      # assigns alice and bob
+/unassign @alice        # removes alice
+```
+
+Users who are already assigned (or, for `/unassign`, not assigned) are skipped. Users
+who cannot be assigned in the repository are skipped with a log message instead of
+failing the run.
+
 ## Testing
 
 Run tests:
@@ -75,9 +107,12 @@ go test -v
 
 ### CLI
 ```bash
-./labeler <labels_url> <owner> <repo> <issue_number> <comment_body> <changed_files>
+./labeler <labels_url> <owner> <repo> <issue_number> <comment_body> <changed_files> [comment_author]
 ```
 
+`comment_author` is optional and only needed for bare `/assign` / `/unassign`. In a
+workflow, pass `${{ github.event.comment.user.login }}`.
+
 ### GitHub Actions Workflow
 The included workflow automatically runs the labeler on issue comments.
 

utilities/labeler/assign_test.go

@@ -0,0 +1,196 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"testing"
+)
+
+func createTestConfigWithAssignRules() *LabelsYAML {
+	return &LabelsYAML{
+		AutoCreate:         false,
+		DefinitionRequired: true,
+		Debug:              true,
+		Ruleset: []Rule{
+			{
+				Name: "assign",
+				Kind: "match",
+				Spec: RuleSpec{Command: "/assign"},
+				Actions: []Action{
+					{Kind: "assign"},
+				},
+			},
+			{
+				Name: "unassign",
+				Kind: "match",
+				Spec: RuleSpec{Command: "/unassign"},
+				Actions: []Action{
+					{Kind: "unassign"},
+				},
+			},
+		},
+	}
+}
+
+func newAssignRequest(body, author string) *LabelRequest {
+	return &LabelRequest{
+		Owner:         "test-owner",
+		Repo:          "test-repo",
+		IssueNumber:   1,
+		CommentBody:   body,
+		CommentAuthor: author,
+	}
+}
+
+func TestLabeler_Assign_ExplicitUsers(t *testing.T) {
+	client := NewMockGitHubClient()
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign @alice bob", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	want := []string{"alice", "bob"}
+	if !slicesEqual(client.AddedAssignees[1], want) {
+		t.Errorf("expected assignees %v to be added, got %v", want, client.AddedAssignees[1])
+	}
+	if len(client.RemovedAssignees[1]) != 0 {
+		t.Errorf("expected no assignees to be removed, got %v", client.RemovedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_NoArgsAssignsCommentAuthor(t *testing.T) {
+	client := NewMockGitHubClient()
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if !slicesEqual(client.AddedAssignees[1], []string{"carol"}) {
+		t.Errorf("expected comment author to be assigned, got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_NoArgsNoAuthorIsNoop(t *testing.T) {
+	client := NewMockGitHubClient()
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	// Without a comment author there is nobody to self-assign; this must not error.
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign", "")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if len(client.AddedAssignees[1]) != 0 {
+		t.Errorf("expected no assignees to be added, got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_SkipsAlreadyAssignedAndDuplicates(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.Assignees[1] = []string{"alice"}
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign @alice @bob @bob", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if !slicesEqual(client.AddedAssignees[1], []string{"bob"}) {
+		t.Errorf("expected only 'bob' to be added, got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_SkipsUnassignableUsers(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.Assignable = []string{"alice"}
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign @alice @stranger", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if !slicesEqual(client.AddedAssignees[1], []string{"alice"}) {
+		t.Errorf("expected only assignable user 'alice' to be added, got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_IsAssigneeErrorIsReported(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.IsAssigneeError = errors.New("boom")
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	// ProcessRequest logs per-rule errors rather than returning them, so assert
+	// on the observable side effect: nothing is assigned on an API error.
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assign @alice", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+	if len(client.AddedAssignees[1]) != 0 {
+		t.Errorf("expected no assignees to be added on IsAssignee error, got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestLabeler_Unassign_ExplicitUsers(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.Assignees[1] = []string{"alice", "bob", "carol"}
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/unassign @alice bob", "dave")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if !slicesEqual(client.RemovedAssignees[1], []string{"alice", "bob"}) {
+		t.Errorf("expected alice and bob to be removed, got %v", client.RemovedAssignees[1])
+	}
+	if !slicesEqual(client.Assignees[1], []string{"carol"}) {
+		t.Errorf("expected carol to remain assigned, got %v", client.Assignees[1])
+	}
+}
+
+func TestLabeler_Unassign_NoArgsRemovesCommentAuthor(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.Assignees[1] = []string{"alice", "carol"}
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/unassign", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if !slicesEqual(client.RemovedAssignees[1], []string{"carol"}) {
+		t.Errorf("expected comment author to be unassigned, got %v", client.RemovedAssignees[1])
+	}
+}
+
+func TestLabeler_Unassign_SkipsUsersNotAssigned(t *testing.T) {
+	client := NewMockGitHubClient()
+	client.Assignees[1] = []string{"alice"}
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/unassign @bob", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+
+	if len(client.RemovedAssignees[1]) != 0 {
+		t.Errorf("expected no removal request for a user who is not assigned, got %v", client.RemovedAssignees[1])
+	}
+}
+
+func TestLabeler_Assign_CommandMustBeOwnToken(t *testing.T) {
+	client := NewMockGitHubClient()
+	labeler := NewLabeler(client, createTestConfigWithAssignRules())
+
+	// "/assignee" must not trigger the "/assign" rule.
+	if err := labeler.ProcessRequest(context.Background(), newAssignRequest("/assignee @alice", "carol")); err != nil {
+		t.Fatalf("ProcessRequest failed: %v", err)
+	}
+	if len(client.AddedAssignees[1]) != 0 {
+		t.Errorf("expected '/assignee' not to match '/assign', got %v", client.AddedAssignees[1])
+	}
+}
+
+func TestNormalizeLogins(t *testing.T) {
+	got := normalizeLogins([]string{"@Alice", "bob", "", "@", "@alice", "Bob"})
+	want := []string{"Alice", "bob"}
+	if !slicesEqual(got, want) {
+		t.Errorf("normalizeLogins = %v, want %v", got, want)
+	}
+}