feat: Assign Reviewers from Gitlab Code Owners Approvers (#98)

* Update gitlab schema to include approval rule data in context

* Require int for an action

* Optional string enum as well

* Schema for assignees and reviewers should unnest from nodes

* Base dry run action

* Add schema for assign reviewers action step

* Get Code owners interface

* Limit reviewers

* Skip bot users

* Set cant guarantee order

* Seed random

* Need user ID to update MR reviewers

* Pass ID to actor

* Parse IDs as ints for create merge request func

* Update pkg/scm/gitlab/client_actioner.go

Co-authored-by: Christian Winther <[email protected]>

* Code review suggestions

* Update nilable rule type

* Actors types

* Also add method

* Remove linear mode

* Append review ids to update

* Fix interface

* Cast context to gitlab context and seperate action into new file

* Add tests for get code owners

* Repackage test

* Tests for assign reviewers acton

* Example

* Should control when reviewers are assigned at action level

* Doc ref to ApprovalRuleType

* Skip id -1 check

* Default to codeowners source

* Add test for higher limit

* Optional limit

* Guard against nil rule type

* Set ctx with random source

* Make action options optional

* Also set enum in json schema

---------

Co-authored-by: Christian Winther <[email protected]>

.scm-engine.gitlab.example.yml

@@ -65,6 +65,16 @@ actions:
       - action: comment
         message: "Approving the MR since it has the 'break-glass-approve' label. Talk to ITGC about this!"
 
+  - name: Assign Reviewers to MR (only when MR is unassigned)
+    group: assign_mr
+    if: |1
+         merge_request.state_is("opened")
+      && not merge_request.approved
+    then:
+      - action: assign_reviewers
+        source: codeowners
+        limit: 1
+
 label:
   - name: lang/go
     color: $indigo

cmd/gitlab_evaluate.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"fmt"
+	"time"
 
 	"github.com/jippi/scm-engine/pkg/config"
 	"github.com/jippi/scm-engine/pkg/scm"
@@ -16,6 +17,7 @@ func Evaluate(cCtx *cli.Context) error {
 	ctx = state.WithProjectID(ctx, cCtx.String(FlagSCMProject))
 	ctx = state.WithToken(ctx, cCtx.String(FlagAPIToken))
 	ctx = state.WithUpdatePipeline(ctx, cCtx.Bool(FlagUpdatePipeline), cCtx.String(FlagUpdatePipelineURL))
+	ctx = state.WithRandomSeed(ctx, time.Now().UnixNano()) // weak seed since only used for codeowner selection
 
 	cfg, err := config.LoadFile(state.ConfigFilePath(ctx))
 	if err != nil {

go.mod

@@ -59,6 +59,7 @@ require (
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/samber/lo v1.47.0 // indirect
 	github.com/sosodev/duration v1.3.1 // indirect
+	github.com/stretchr/objx v0.5.2 // indirect
 	github.com/xrash/smetrics v0.0.0-20240521201337-686a1a2994c1 // indirect
 	golang.org/x/mod v0.20.0 // indirect
 	golang.org/x/sync v0.10.0 // indirect

go.sum

@@ -112,6 +112,8 @@ github.com/sergi/go-diff v1.3.1/go.mod h1:aMJSSKb2lpPvRNec0+w3fl7LP9IOFzdc9Pa4NF
 github.com/sosodev/duration v1.3.1 h1:qtHBDMQ6lvMQsL15g4aopM4HEfOaYuhWBw3NPTtlqq4=
 github.com/sosodev/duration v1.3.1/go.mod h1:RQIBBX0+fMLc/D9+Jb/fwvVmo0eZvDDEERAikUR6SDg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=

pkg/config/action_step.go

@@ -16,6 +16,7 @@ type actionList struct {
 var actions = []actionList{
 	{name: "add_label", instance: AddLabelAction{}},
 	{name: "approve", instance: ApproveAction{}},
+	{name: "assign_reviewers", instance: AssignReviewers{}},
 	{name: "close", instance: CloseAction{}},
 	{name: "comment", instance: CommentAction{}},
 	{name: "lock_discussion", instance: LockDiscussionAction{}},
@@ -72,6 +73,17 @@ type CommentAction struct {
 	Message string `json:"message" yaml:"message"`
 }
 
+type AssignReviewers struct {
+	BaseAction
+
+	// The source of the reviewers
+	Source *string `json:"source,omitempty" yaml:"source,omitempty" jsonschema:"enum=codeowners"`
+	// The max number of reviewers to assign
+	Limit int `json:"limit,omitempty" yaml:"limit,omitempty"`
+	// The mode of assigning reviewers
+	Mode string `json:"mode,omitempty" yaml:"mode,omitempty" jsonschema:"enum=random"`
+}
+
 type AddLabelAction struct {
 	BaseAction
 
@@ -149,6 +161,20 @@ func (step ActionStep) JSONSchema() *jsonschema.Schema {
 	}
 }
 
+func (step ActionStep) RequiredInt(name string) (int, error) {
+	value, ok := step[name]
+	if !ok {
+		return 0, fmt.Errorf("Required 'step' key '%s' is missing", name)
+	}
+
+	valueInt, ok := value.(int)
+	if !ok {
+		return 0, fmt.Errorf("Required 'step' key '%s' must be of type int, got %T", name, value)
+	}
+
+	return valueInt, nil
+}
+
 func (step ActionStep) RequiredString(name string) (string, error) {
 	value, ok := step[name]
 	if !ok {
@@ -163,6 +189,40 @@ func (step ActionStep) RequiredString(name string) (string, error) {
 	return valueString, nil
 }
 
+func (step ActionStep) RequiredStringEnum(name string, values ...string) (string, error) {
+	value, ok := step[name]
+	if !ok {
+		return "", fmt.Errorf("Required 'step' key '%s' is missing", name)
+	}
+
+	valueString, ok := value.(string)
+	if !ok {
+		return "", fmt.Errorf("Required 'step' key '%s' must be of type string, got %T", name, value)
+	}
+
+	for _, validValue := range values {
+		if valueString == validValue {
+			return valueString, nil
+		}
+	}
+
+	return "", fmt.Errorf("Required 'step' key '%s' must be one of %v, got %s", name, values, valueString)
+}
+
+func (step ActionStep) OptionalInt(name string, fallback int) (int, error) {
+	value, ok := step[name]
+	if !ok {
+		return fallback, nil
+	}
+
+	valueInt, ok := value.(int)
+	if !ok {
+		return fallback, fmt.Errorf("Optional step field '%s' must be of type int, got %T", name, value)
+	}
+
+	return valueInt, nil
+}
+
 func (step ActionStep) OptionalString(name, defaultValue string) (string, error) {
 	value, ok := step[name]
 	if !ok {
@@ -177,6 +237,26 @@ func (step ActionStep) OptionalString(name, defaultValue string) (string, error)
 	return valueString, nil
 }
 
+func (step ActionStep) OptionalStringEnum(name string, fallback string, values ...string) (string, error) {
+	value, ok := step[name]
+	if !ok {
+		return fallback, nil
+	}
+
+	valueString, ok := value.(string)
+	if !ok {
+		return fallback, fmt.Errorf("Optional step field '%s' must be of type string, got %T", name, value)
+	}
+
+	for _, validValue := range values {
+		if valueString == validValue {
+			return valueString, nil
+		}
+	}
+
+	return fallback, fmt.Errorf("Optional step field '%s' must be one of %v, got %s", name, values, valueString)
+}
+
 func (step ActionStep) Get(name string) (any, error) {
 	value, ok := step[name]
 	if !ok {

pkg/scm/github/context.go

@@ -113,3 +113,13 @@ func (c *Context) HasExecutedActionGroup(name string) bool {
 func (c *Context) AllowPipelineFailure(ctx context.Context) bool {
 	return len(c.PullRequest.findModifiedFiles(state.ConfigFilePath(ctx))) == 1
 }
+
+func (c *Context) GetCodeOwners() scm.Actors {
+	// unimplemented
+	return make(scm.Actors, 0)
+}
+
+func (c *Context) GetReviewers() scm.Actors {
+	// unimplemented
+	return make(scm.Actors, 0)
+}

pkg/scm/gitlab/client_actioner.go

@@ -153,6 +153,9 @@ func (c *Client) ApplyStep(ctx context.Context, evalContext scm.EvalContext, upd
 
 		return err
 
+	case "assign_reviewers":
+		return c.AssignReviewers(ctx, evalContext, update, step)
+
 	case "comment":
 		message, err := step.RequiredString("message")
 		if err != nil {

pkg/scm/gitlab/client_actioner_assign.go

@@ -0,0 +1,96 @@
+package gitlab
+
+import (
+	"context"
+	"log/slog"
+
+	"github.com/jippi/scm-engine/pkg/scm"
+	"github.com/jippi/scm-engine/pkg/state"
+	slogctx "github.com/veqryn/slog-context"
+)
+
+func (c *Client) AssignReviewers(ctx context.Context, evalContext scm.EvalContext, update *scm.UpdateMergeRequestOptions, step scm.ActionStep) error {
+	source, err := step.OptionalStringEnum("source", "codeowners", "codeowners")
+	if err != nil {
+		return err
+	}
+
+	desiredLimit, err := step.OptionalInt("limit", 1)
+	if err != nil {
+		return err
+	}
+
+	mode, err := step.OptionalStringEnum("mode", "random", "random")
+	if err != nil {
+		return err
+	}
+
+	// prevents misuse and situations where evaluate will assign reviewers endlessly
+	existingReviewers := evalContext.GetReviewers()
+	if len(existingReviewers) > 0 {
+		slogctx.Debug(ctx, "Reviewers already assigned", slog.Any("reviewers", existingReviewers))
+
+		return nil
+	}
+
+	var eligibleReviewers []scm.Actor
+
+	switch source {
+	case "codeowners":
+		eligibleReviewers = evalContext.GetCodeOwners()
+
+		break
+	}
+
+	if len(eligibleReviewers) == 0 {
+		slogctx.Debug(ctx, "No eligible reviewers found")
+
+		return nil
+	}
+
+	var reviewers scm.Actors
+
+	limit := desiredLimit
+	if limit > len(eligibleReviewers) {
+		limit = len(eligibleReviewers)
+	}
+
+	switch mode {
+	case "random":
+		reviewers = make(scm.Actors, limit)
+
+		rand := state.RandomSeed(ctx)
+		perm := rand.Perm(len(eligibleReviewers))
+
+		for i := 0; i < limit; i++ {
+			reviewers[i] = eligibleReviewers[perm[i]]
+		}
+
+		break
+	}
+
+	reviewerIDs := make([]int, 0, len(reviewers))
+
+	for _, reviewer := range reviewers {
+		id := reviewer.IntID()
+
+		// skip invalid int ids, this should not happen but still safeguard against it
+		if id == 0 {
+			slogctx.Warn(ctx, "Invalid reviewer ID", slog.String("id", reviewer.ID))
+
+			continue
+		}
+
+		reviewerIDs = append(reviewerIDs, id)
+	}
+
+	if state.IsDryRun(ctx) {
+		slogctx.Info(ctx, "(Dry Run) Assigning MR", slog.String("source", source), slog.Int("limit", limit), slog.String("mode", mode), slog.Any("reviewers", reviewers))
+
+		return nil
+	}
+
+	update.AppendReviewerIDs(reviewerIDs)
+
+	return nil
+}