feat: inject review summary into MR/PR description (#45)

.code-reviewer.example.yaml

@@ -27,6 +27,8 @@ comment_mode: notes
 
 # cleanup_mode: delete    # How to handle previous bot comments (delete or resolve)
 
+# update_description: false  # Inject review summary into MR/PR description
+
 # How to handle diffs that exceed the model's context window.
 # fail: error out with a helpful message (default, forces smaller MRs)
 # split: auto-split into chunks and merge results

internal/config/config.go

@@ -114,6 +114,7 @@ type Config struct {
 	NoColor     bool   // Disable ANSI color output.
 	SARIFOutput string // Path to write SARIF 2.1.0 output file.
 	ProxyURL    string // Optional: LLM proxy URL for observability (e.g., Candela).
+	UpdateDescription bool
 
 	// GitLab settings.
 	GitLabToken   string
@@ -174,6 +175,7 @@ type repoConfig struct {
 	APIURL                   string   `yaml:"api_url"`
 	Summarize                bool     `yaml:"summarize"`
 	SummaryUpdateDescription bool     `yaml:"summary_update_description"`
+	UpdateDescription        *bool    `yaml:"update_description"`
 	IntentReview             *bool    `yaml:"intent_review"`
 }
 
@@ -352,6 +354,9 @@ func (c *Config) applyRepoConfig(data []byte) error {
 	if rc.SummaryUpdateDescription {
 		c.SummaryUpdateDescription = true
 	}
+	if rc.UpdateDescription != nil {
+		c.UpdateDescription = *rc.UpdateDescription
+	}
 	if rc.IntentReview != nil {
 		c.IntentReview = *rc.IntentReview
 		if !*rc.IntentReview {
@@ -379,6 +384,9 @@ func (c *Config) loadEnv() {
 	if v := os.Getenv("CODE_REVIEWER_CLEANUP_MODE"); v != "" {
 		c.CleanupMode = CleanupMode(v)
 	}
+	if v := os.Getenv("CODE_REVIEWER_UPDATE_DESCRIPTION"); strings.EqualFold(v, "true") {
+		c.UpdateDescription = true
+	}
 	if v := os.Getenv("REVIEW_CHUNK_STRATEGY"); v != "" {
 		c.ChunkStrategy = ChunkStrategy(v)
 	}
@@ -480,6 +488,7 @@ func (c *Config) loadFlags() error {
 	apiKey := fs.String("api-key", "", "API key for HTTP provider (optional for IAM/ADC auth)")
 	summarize := fs.Bool("summarize", false, "Generate MR summary instead of review")
 	summaryUpdateDesc := fs.Bool("summary-update-description", false, "Update MR description with the generated summary")
+	updateDesc := fs.Bool("update-description", false, "Inject review summary into MR/PR description")
 	intentFlag := fs.Bool("intent", false, "Enable two-pass intent-aware review")
 	noIntentFlag := fs.Bool("no-intent", false, "Disable intent-aware review (overrides CI default)")
 	explain := fs.Bool("explain", false, "Explain the diff instead of reviewing it")
@@ -577,6 +586,9 @@ func (c *Config) loadFlags() error {
 	if *summaryUpdateDesc {
 		c.SummaryUpdateDescription = true
 	}
+	if *updateDesc {
+		c.UpdateDescription = true
+	}
 	if *intentFlag {
 		c.IntentReview = true
 	}

internal/config/config_test.go

@@ -734,6 +734,26 @@ func TestLoad_FlagAndEnvOptions(t *testing.T) {
 				}
 			},
 		},
+		{
+			name: "update_description_flag",
+			args: []string{"code-reviewer", "--diff", "--update-description"},
+			env:  map[string]string{"GOOGLE_CLOUD_PROJECT": "test-project"},
+			assert: func(t *testing.T, cfg *Config) {
+				if !cfg.UpdateDescription {
+					t.Errorf("UpdateDescription = false, want true")
+				}
+			},
+		},
+		{
+			name: "update_description_env",
+			args: []string{"code-reviewer", "--diff"},
+			env:  map[string]string{"GOOGLE_CLOUD_PROJECT": "test-project", "CODE_REVIEWER_UPDATE_DESCRIPTION": "true"},
+			assert: func(t *testing.T, cfg *Config) {
+				if !cfg.UpdateDescription {
+					t.Errorf("UpdateDescription = false, want true")
+				}
+			},
+		},
 	}
 
 	for _, tt := range tests {

internal/github/client.go

@@ -109,6 +109,31 @@ func (c *Client) GetMRVersions(ctx context.Context, projectID, prNumber string)
 	}, nil
 }
 
+// GetDescription returns the current body of a pull request.
+func (c *Client) GetDescription(ctx context.Context, owner, prNumber string) (string, error) {
+	apiURL := fmt.Sprintf("%s/repos/%s/pulls/%s", c.baseURL, owner, prNumber)
+	var pr struct {
+		Body string `json:"body"`
+	}
+	if err := c.get(ctx, apiURL, &pr); err != nil {
+		return "", fmt.Errorf("getting PR description: %w", err)
+	}
+	return pr.Body, nil
+}
+
+// SetDescription updates the body of a pull request.
+func (c *Client) SetDescription(ctx context.Context, owner, prNumber, description string) error {
+	apiURL := fmt.Sprintf("%s/repos/%s/pulls/%s", c.baseURL, owner, prNumber)
+	type descReq struct {
+		Body string `json:"body"`
+	}
+	data, err := json.Marshal(descReq{Body: description})
+	if err != nil {
+		return err
+	}
+	return c.do(ctx, http.MethodPatch, apiURL, bytes.NewReader(data), "application/json", nil)
+}
+
 // CompareCommits returns the list of files changed between two commits.
 func (c *Client) CompareCommits(ctx context.Context, projectID, from, to string) ([]string, error) {
 	apiURL := fmt.Sprintf("%s/repos/%s/compare/%s...%s", c.baseURL, projectID, url.PathEscape(from), url.PathEscape(to))
@@ -244,12 +269,18 @@ func (c *Client) SubmitReview(ctx context.Context, projectID, prNumber string, r
 		if comment.Suggestion != "" {
 			commentBody += fmt.Sprintf("\n\n```suggestion\n%s\n```", comment.Suggestion)
 		}
-		validComments = append(validComments, ReviewCommentRequest{
+		rc := ReviewCommentRequest{
 			Path: comment.Path,
 			Line: comment.Line,
 			Body: commentBody,
 			Side: "RIGHT",
-		})
+		}
+		if comment.EndLine > comment.Line {
+			startLine := comment.Line
+			rc.StartLine = &startLine
+			rc.Line = comment.EndLine
+		}
+		validComments = append(validComments, rc)
 	}
 	if dropped > 0 {
 		slog.Info("pre-validation filtered comments", "valid", len(validComments), "dropped", dropped)

internal/github/types.go

@@ -117,6 +117,8 @@ type CreateReviewRequest struct {
 type ReviewCommentRequest struct {
 	// Path is the file path for the comment.
 	Path string `json:"path"`
+	// StartLine is the start line number for the comment (optional).
+	StartLine *int `json:"start_line,omitempty"`
 	// Line is the line number for the comment.
 	Line int    `json:"line"`
 	// Body is the text content of the inline comment.

internal/gitlab/client.go

@@ -107,6 +107,27 @@ func (c *Client) GetMRVersions(ctx context.Context, projectID, mrIID string) ([]
 	return result, nil
 }
 
+// GetDescription returns the current description of a merge request.
+func (c *Client) GetDescription(ctx context.Context, projectID, mrIID string) (string, error) {
+	apiURL := fmt.Sprintf("%s/projects/%s/merge_requests/%s", c.baseURL, url.PathEscape(projectID), mrIID)
+	var mr struct {
+		Description string `json:"description"`
+	}
+	if err := c.get(ctx, apiURL, &mr); err != nil {
+		return "", fmt.Errorf("getting MR description: %w", err)
+	}
+	return mr.Description, nil
+}
+
+// SetDescription updates the description of a merge request.
+func (c *Client) SetDescription(ctx context.Context, projectID, mrIID, description string) error {
+	apiURL := fmt.Sprintf("%s/projects/%s/merge_requests/%s", c.baseURL, url.PathEscape(projectID), mrIID)
+	type descReq struct {
+		Description string `json:"description"`
+	}
+	return c.put(ctx, apiURL, descReq{Description: description}, nil)
+}
+
 // PostNote creates a simple note (comment) on a merge request.
 func (c *Client) PostNote(ctx context.Context, projectID, mrIID, body string) (*vcs.Comment, error) {
 	url := fmt.Sprintf("%s/projects/%s/merge_requests/%s/notes", c.baseURL, url.PathEscape(projectID), mrIID)
@@ -138,6 +159,12 @@ func (c *Client) CreateDiscussion(ctx context.Context, projectID, mrIID string,
 			OldLine:      req.Position.OldLine,
 			NewLine:      req.Position.NewLine,
 		}
+		if req.Position.EndLine != nil && req.Position.NewLine != nil {
+			glReq.Position.LineRange = &DiscussionLineRange{
+				Start: DiscussionLineRef{NewLine: *req.Position.NewLine, Type: "new"},
+				End:   DiscussionLineRef{NewLine: *req.Position.EndLine, Type: "new"},
+			}
+		}
 	}
 
 	if err := c.post(ctx, url, glReq, nil); err != nil {
@@ -333,7 +360,12 @@ func (c *Client) submitViaDraftNotes(ctx context.Context, projectID, mrIID strin
 			newLine := comment.Line
 			noteBody := comment.Body
 			if comment.Suggestion != "" {
-				noteBody += fmt.Sprintf("\n\n```suggestion:-0+0\n%s\n```", comment.Suggestion)
+				if comment.EndLine > comment.Line {
+					offset := comment.EndLine - comment.Line
+					noteBody += fmt.Sprintf("\n\n```suggestion:-%d+0\n%s\n```", offset, comment.Suggestion)
+				} else {
+					noteBody += fmt.Sprintf("\n\n```suggestion:-0+0\n%s\n```", comment.Suggestion)
+				}
 			}
 			draftReq := CreateDraftNoteRequest{
 				Note: noteBody + "\n" + botMarker,
@@ -347,6 +379,12 @@ func (c *Client) submitViaDraftNotes(ctx context.Context, projectID, mrIID strin
 					NewLine:      &newLine,
 				},
 			}
+			if comment.EndLine > comment.Line {
+				draftReq.Position.LineRange = &DiscussionLineRange{
+					Start: DiscussionLineRef{NewLine: comment.Line, Type: "new"},
+					End:   DiscussionLineRef{NewLine: comment.EndLine, Type: "new"},
+				}
+			}
 			if _, err := c.createDraftNote(ctx, projectID, mrIID, draftReq); err != nil {
 				// Fallback: post as a regular note so feedback is not lost.
 				slog.Warn("draft creation failed, posting as note fallback",
@@ -398,7 +436,12 @@ func (c *Client) submitViaIndividualComments(ctx context.Context, projectID, mrI
 			newLine := comment.Line
 			noteBody := comment.Body
 			if comment.Suggestion != "" {
-				noteBody += fmt.Sprintf("\n\n```suggestion:-0+0\n%s\n```", comment.Suggestion)
+				if comment.EndLine > comment.Line {
+					offset := comment.EndLine - comment.Line
+					noteBody += fmt.Sprintf("\n\n```suggestion:-%d+0\n%s\n```", offset, comment.Suggestion)
+				} else {
+					noteBody += fmt.Sprintf("\n\n```suggestion:-0+0\n%s\n```", comment.Suggestion)
+				}
 			}
 			inlineReq := vcs.InlineCommentRequest{
 				Body: noteBody,
@@ -411,6 +454,10 @@ func (c *Client) submitViaIndividualComments(ctx context.Context, projectID, mrI
 					NewLine:  &newLine,
 				},
 			}
+			if comment.EndLine > comment.Line {
+				endLine := comment.EndLine
+				inlineReq.Position.EndLine = &endLine
+			}
 
 			if err := c.CreateDiscussion(ctx, projectID, mrIID, inlineReq); err != nil {
 				slog.Warn("failed to create inline discussion, posting as note instead",

internal/gitlab/types.go

@@ -100,6 +100,16 @@ type Author struct {
 	Name     string `json:"name"`
 }
 
+type DiscussionLineRef struct {
+	NewLine int    `json:"new_line"`
+	Type    string `json:"type"` // "new"
+}
+
+type DiscussionLineRange struct {
+	Start DiscussionLineRef `json:"start"`
+	End   DiscussionLineRef `json:"end"`
+}
+
 // DiscussionPosition specifies where an inline comment should be anchored in the diff.
 type DiscussionPosition struct {
 	PositionType string `json:"position_type"`
@@ -108,8 +118,9 @@ type DiscussionPosition struct {
 	StartSHA     string `json:"start_sha"`
 	OldPath      string `json:"old_path,omitempty"`
 	NewPath      string `json:"new_path"`
-	OldLine      *int   `json:"old_line,omitempty"`
-	NewLine      *int   `json:"new_line,omitempty"`
+	OldLine      *int                 `json:"old_line,omitempty"`
+	NewLine      *int                 `json:"new_line,omitempty"`
+	LineRange    *DiscussionLineRange `json:"line_range,omitempty"`
 }
 
 // CreateDiscussionRequest is the request body for creating an inline discussion.

internal/model/prompt.go

@@ -59,6 +59,7 @@ You MUST respond with a valid JSON object matching this exact schema. Do NOT inc
     {
       "file": "path/to/file.go",
       "line": 42,
+      "end_line": 45,
       "severity": "HIGH",
       "category": "bug",
       "title": "Single sentence summary of the issue",
@@ -71,7 +72,7 @@ You MUST respond with a valid JSON object matching this exact schema. Do NOT inc
 If no issues are found, return:
 {"summary": "description of the change", "findings": []}
 
-The "line" field MUST correspond to the new_line number shown in the diff. The "category" MUST be one of: bug, security, performance, style, docs, scope. Use "scope" ONLY for intent-driven findings (e.g., scope creep, missing tests for new features). Do NOT use "scope" to suggest splitting or resizing the change.
+The "line" field MUST correspond to the new_line number shown in the diff. The "end_line" field is optional and represents the last line of the finding range. Omit for single-line findings. The "category" MUST be one of: bug, security, performance, style, docs, scope. Use "scope" ONLY for intent-driven findings (e.g., scope creep, missing tests for new features). Do NOT use "scope" to suggest splitting or resizing the change.
 
 ## SUGGESTION RULES
 

internal/model/provider.go

@@ -29,6 +29,7 @@ type ReviewResult struct {
 type Finding struct {
 	File       string `json:"file"`
 	Line       int    `json:"line"`
+	EndLine    int    `json:"end_line,omitempty"`
 	Severity   string `json:"severity"`
 	Category   string `json:"category"`
 	Title      string `json:"title"`
@@ -172,6 +173,14 @@ func parseReviewJSON(text string) (*ReviewResult, error) {
 	if err := json.Unmarshal([]byte(cleaned), &result); err != nil {
 		return nil, fmt.Errorf("could not parse model response as JSON: %w", err)
 	}
+
+	for i := range result.Findings {
+		f := &result.Findings[i]
+		if f.EndLine != 0 && f.EndLine < f.Line {
+			f.EndLine = 0 // Invalid range, fall back to single-line
+		}
+	}
+
 	return &result, nil
 }
 

internal/reviewer/description.go

@@ -0,0 +1,31 @@
+package reviewer
+
+import (
+	"fmt"
+	"strings"
+)
+
+const (
+	descMarkerStart = "<!-- code-reviewer:start -->"
+	descMarkerEnd   = "<!-- code-reviewer:end -->"
+)
+
+// buildDescriptionSection wraps the review summary in HTML comment markers.
+func buildDescriptionSection(summary string) string {
+	return fmt.Sprintf("%s\n%s\n%s", descMarkerStart, summary, descMarkerEnd)
+}
+
+// replaceDescriptionSection replaces or appends the review section in a description.
+func replaceDescriptionSection(existing, section string) string {
+	startIdx := strings.Index(existing, descMarkerStart)
+	endIdx := strings.Index(existing, descMarkerEnd)
+	if startIdx >= 0 && endIdx >= 0 {
+		endIdx += len(descMarkerEnd)
+		return existing[:startIdx] + section + existing[endIdx:]
+	}
+	// Append with separator.
+	if existing != "" {
+		return existing + "\n\n---\n\n" + section
+	}
+	return section
+}