Custom PR template: default behavior is to append generated SPR body

github/template/template_custom/template.go

@@ -1,6 +1,7 @@
 package template_custom
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"path"
@@ -78,6 +79,16 @@ func (t *CustomTemplatizer) readPRTemplate() (string, error) {
 	return string(pullRequestTemplateBytes), nil
 }
 
+const (
+	// Default anchors mark where the stack content is inserted in PR templates.
+	// Can be overridden in RepoConfig using PRTemplateInsertStart and PRTemplateInsertEnd.
+	// If anchors are not found in the template, content is appended to the PR.
+	// Implemented as HTML comments so they don't appear in rendered Markdown.
+
+	defaultStartAnchor = "<!-- SPR-STACK-START -->"
+	defaultEndAnchor   = "<!-- SPR-STACK-END -->"
+)
+
 // insertBodyIntoPRTemplate inserts a text body into the given PR template and returns the result as a string.
 // It uses the PRTemplateInsertStart and PRTemplateInsertEnd values defined in RepoConfig to determine where the body
 // should be inserted in the PR template. If there are issues finding the correct place to insert the body
@@ -91,40 +102,67 @@ func (t *CustomTemplatizer) insertBodyIntoPRTemplate(body, prTemplate string, pr
 		templateOrExistingPRBody = pr.Body
 	}
 
-	startPRTemplateSection, err := getSectionOfPRTemplate(templateOrExistingPRBody, t.repoConfig.PRTemplateInsertStart, BeforeMatch)
+	startAnchor := t.repoConfig.PRTemplateInsertStart
+	if startAnchor == "" {
+		startAnchor = defaultStartAnchor
+	}
+
+	endAnchor := t.repoConfig.PRTemplateInsertEnd
+	if endAnchor == "" {
+		endAnchor = defaultEndAnchor
+	}
+
+	startPRTemplateSection, err := getSectionOfPRTemplate(templateOrExistingPRBody, startAnchor, BeforeMatch)
+	if err == ErrNoMatchesFound && startAnchor == defaultStartAnchor {
+		// Default append mode: if no anchors found in the template, append body at the end.
+		return fmt.Sprintf("%s\n\n%s\n%s\n\n%s\n", templateOrExistingPRBody, startAnchor, body, endAnchor), nil
+	}
+
 	if err != nil {
-		return "", fmt.Errorf("%w: PR template insert start = '%v'", err, t.repoConfig.PRTemplateInsertStart)
+		return "", fmt.Errorf("%w: PR template insert start = '%v'", err, startAnchor)
 	}
 
-	endPRTemplateSection, err := getSectionOfPRTemplate(templateOrExistingPRBody, t.repoConfig.PRTemplateInsertEnd, AfterMatch)
+	endPRTemplateSection, err := getSectionOfPRTemplate(templateOrExistingPRBody, endAnchor, AfterMatch)
 	if err != nil {
-		return "", fmt.Errorf("%w: PR template insert end = '%v'", err, t.repoConfig.PRTemplateInsertEnd)
+		return "", fmt.Errorf("%w: PR template insert end = '%v'", err, endAnchor)
 	}
 
-	return fmt.Sprintf("%v%v\n%v\n\n%v%v", startPRTemplateSection, t.repoConfig.PRTemplateInsertStart, body,
-		t.repoConfig.PRTemplateInsertEnd, endPRTemplateSection), nil
+	return fmt.Sprintf("%v%v\n%v\n\n%v%v", startPRTemplateSection, startAnchor, body, endAnchor, endPRTemplateSection), nil
 }
 
 const (
 	BeforeMatch = iota
 	AfterMatch
 )
 
+var (
+	// Error returned when no matches are found in a PR template
+	ErrNoMatchesFound = fmt.Errorf("no matches found")
+	// Error returned when multiple matches are found in a PR template
+	ErrMultipleMatchesFound = fmt.Errorf("multiple matches found")
+)
+
 // getSectionOfPRTemplate searches text for a matching searchString and will return the text before or after the
 // match as a string. If there are no matches or more than one match is found, an error will be returned.
 func getSectionOfPRTemplate(text, searchString string, returnMatch int) (string, error) {
-	split := strings.Split(text, searchString)
-	switch len(split) {
-	case 2:
-		if returnMatch == BeforeMatch {
-			return split[0], nil
-		} else if returnMatch == AfterMatch {
-			return split[1], nil
-		}
-		return "", fmt.Errorf("invalid enum value")
+	// Check occurrence count in a single pass
+	count := strings.Count(text, searchString)
+	switch count {
+	case 0:
+		return "", ErrNoMatchesFound
 	case 1:
-		return "", fmt.Errorf("no matches found")
+		// Expected case: exactly one match
+		idx := strings.Index(text, searchString)
+		switch returnMatch {
+		case BeforeMatch:
+			return text[:idx], nil
+		case AfterMatch:
+			return text[idx+len(searchString):], nil
+		default:
+			return "", errors.New("invalid enum value")
+		}
 	default:
-		return "", fmt.Errorf("multiple matches found")
+		// count > 1
+		return "", ErrMultipleMatchesFound
 	}
 }

github/template/template_custom/template_test.go

@@ -2,6 +2,7 @@ package template_custom
 
 import (
 	"context"
+	"errors"
 	"os"
 	"path/filepath"
 	"strings"
@@ -514,3 +515,172 @@ func TestFormatBodyCurrentCommitIndicator(t *testing.T) {
 	assert.Contains(t, result, "#2 ⬅")
 	assert.NotContains(t, result, "#1 ⬅")
 }
+
+// TestInsertBodyIntoPRTemplateDefaultAnchors tests default anchor behavior for creation, replacement, and update scenarios
+func TestInsertBodyIntoPRTemplateDefaultAnchors(t *testing.T) {
+	tests := []struct {
+		name          string
+		prTemplate    string
+		body          string
+		pr            *github.PullRequest
+		expectedError error
+		expected      string
+	}{
+		{
+			name: "no_markers_exist_append_with_default_anchors",
+			prTemplate: `
+# PR Template
+
+content
+`,
+			body:          "Generated body content",
+			pr:            nil,
+			expectedError: nil,
+			expected: `
+# PR Template
+
+content
+
+
+<!-- SPR-STACK-START -->
+Generated body content
+
+<!-- SPR-STACK-END -->
+`,
+		},
+		{
+			name: "existing_markers_replace_content_between_default_anchors",
+			prTemplate: `
+# PR Template
+
+content before markers
+
+<!-- SPR-STACK-START -->
+	old spr stack goes here (to be replaced)
+<!-- SPR-STACK-END -->
+`,
+			body:          "New commit body",
+			pr:            nil,
+			expectedError: nil,
+			expected: `
+# PR Template
+
+content before markers
+
+<!-- SPR-STACK-START -->
+New commit body
+
+<!-- SPR-STACK-END -->
+`,
+		},
+		{
+			name: "pr_update_use_existing_PR_body_and_replace_content",
+			prTemplate: `# PR Template
+
+Initial description
+`,
+			body: "Updated commit body",
+			pr: &github.PullRequest{
+				Body: `# PR Template
+
+Initial description
+
+<!-- SPR-STACK-START -->
+Old body content
+
+<!-- SPR-STACK-END -->
+`,
+			},
+			expectedError: nil,
+			expected: `# PR Template
+
+Initial description
+
+<!-- SPR-STACK-START -->
+Updated commit body
+
+<!-- SPR-STACK-END -->
+`,
+		},
+		{
+			name: "error_missing_end_anchor_in_existing_PR_body",
+			prTemplate: `# PR Template
+
+description
+`,
+			body: "New body",
+			pr: &github.PullRequest{
+				Body: `# PR Template
+
+description
+
+<!-- SPR-STACK-START -->
+Old content
+`,
+			},
+			expectedError: ErrNoMatchesFound,
+			expected:      "",
+		},
+		{
+			name: "error_multiple_start_anchors_in_existing_PR_body",
+			prTemplate: `# PR Template
+
+description
+`,
+			body: "New body",
+			pr: &github.PullRequest{
+				Body: `# PR Template
+
+<!-- SPR-STACK-START -->
+Content 1
+<!-- SPR-STACK-START -->
+Content 2
+<!-- SPR-STACK-END -->
+`,
+			},
+			expectedError: ErrMultipleMatchesFound,
+			expected:      "",
+		},
+		{
+			name: "error_multiple_end_anchors_in_existing_PR_body",
+			prTemplate: `# PR Template
+
+description
+`,
+			body: "New body",
+			pr: &github.PullRequest{
+				Body: `# PR Template
+
+<!-- SPR-STACK-START -->
+Content
+<!-- SPR-STACK-END -->
+More content
+<!-- SPR-STACK-END -->
+`,
+			},
+			expectedError: ErrMultipleMatchesFound,
+			expected:      "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			repoConfig := &config.RepoConfig{
+				PRTemplatePath: "pr_template.md",
+				// No custom anchors - use defaults
+			}
+			gitcmd := &mockGit{rootDir: "/tmp"}
+			templatizer := NewCustomTemplatizer(repoConfig, gitcmd)
+
+			result, err := templatizer.insertBodyIntoPRTemplate(tt.body, tt.prTemplate, tt.pr)
+
+			if tt.expectedError != nil {
+				assert.True(t, errors.Is(err, tt.expectedError), "expected error %v, got %v", tt.expectedError, err)
+				return
+			}
+
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}