GC: Iteration Cleanup (#878)

## Description
Small refactor. Moves Path functions from iterator to `service_functions.go`
Introduces getCollectionPath which combines the two previous functions and reduces code complexity
## Type of change

<!--- Please check the type of change your PR introduces: --->
- [x] 🐹 Trivial/Minor

## Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #<issue>

## Test Plan

- [x] ⚡ Unit test

src/internal/connector/exchange/service_functions.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/alcionai/corso/src/internal/connector/graph"
 	"github.com/alcionai/corso/src/internal/connector/support"
+	"github.com/alcionai/corso/src/internal/path"
 	"github.com/alcionai/corso/src/pkg/account"
 	"github.com/alcionai/corso/src/pkg/selectors"
 )
@@ -354,3 +355,103 @@ func SetupExchangeCollectionVars(scope selectors.ExchangeScope) (
 
 	return nil, nil, nil, errors.New("exchange scope option not supported")
 }
+
+// maybeGetAndPopulateFolderResolver gets a folder resolver if one is available for
+// this category of data. If one is not available, returns nil so that other
+// logic in the caller can complete as long as they check if the resolver is not
+// nil. If an error occurs populating the resolver, returns an error.
+func maybeGetAndPopulateFolderResolver(
+	ctx context.Context,
+	qp graph.QueryParams,
+	category path.CategoryType,
+) (graph.ContainerResolver, error) {
+	var res graph.ContainerResolver
+
+	switch category {
+	case path.EmailCategory:
+		service, err := createService(qp.Credentials, qp.FailFast)
+		if err != nil {
+			return nil, err
+		}
+
+		res = &mailFolderCache{
+			userID: qp.User,
+			gs:     service,
+		}
+
+	default:
+		return nil, nil
+	}
+
+	if err := res.Populate(ctx); err != nil {
+		return nil, errors.Wrap(err, "populating directory resolver")
+	}
+
+	return res, nil
+}
+
+func resolveCollectionPath(
+	ctx context.Context,
+	resolver graph.ContainerResolver,
+	tenantID, user, folderID string,
+	category path.CategoryType,
+) (path.Path, error) {
+	if resolver == nil {
+		// Allows caller to default to old-style path.
+		return nil, errors.WithStack(errNilResolver)
+	}
+
+	p, err := resolver.IDToPath(ctx, folderID)
+	if err != nil {
+		return nil, errors.Wrap(err, "resolving folder ID")
+	}
+
+	return p.ToDataLayerExchangePathForCategory(
+		tenantID,
+		user,
+		category,
+		false,
+	)
+}
+
+func getCollectionPath(
+	ctx context.Context,
+	qp graph.QueryParams,
+	resolver graph.ContainerResolver,
+	directory string,
+	category path.CategoryType,
+) (path.Path, error) {
+	returnPath, err := resolveCollectionPath(
+		ctx,
+		resolver,
+		qp.Credentials.TenantID,
+		qp.User,
+		directory,
+		category,
+	)
+	if err == nil {
+		return returnPath, nil
+	}
+
+	aPath, err1 := path.Builder{}.Append(directory).
+		ToDataLayerExchangePathForCategory(
+			qp.Credentials.TenantID,
+			qp.User,
+			category,
+			false,
+		)
+	if err1 == nil {
+		return aPath, nil
+	}
+
+	return nil,
+		support.WrapAndAppend(
+			fmt.Sprintf(
+				"both path generate functions failed for %s:%s:%s",
+				qp.User,
+				category,
+				directory),
+			err,
+			err1,
+		)
+}

src/internal/connector/exchange/service_iterators.go

@@ -25,64 +25,6 @@ type GraphIterateFunc func(
 	statusUpdater support.StatusUpdater,
 ) func(any) bool
 
-// maybeGetAndPopulateFolderResolver gets a folder resolver if one is available for
-// this category of data. If one is not available, returns nil so that other
-// logic in the caller can complete as long as they check if the resolver is not
-// nil. If an error occurs populating the resolver, returns an error.
-func maybeGetAndPopulateFolderResolver(
-	ctx context.Context,
-	qp graph.QueryParams,
-	category path.CategoryType,
-) (graph.ContainerResolver, error) {
-	var res graph.ContainerResolver
-
-	switch category {
-	case path.EmailCategory:
-		service, err := createService(qp.Credentials, qp.FailFast)
-		if err != nil {
-			return nil, err
-		}
-
-		res = &mailFolderCache{
-			userID: qp.User,
-			gs:     service,
-		}
-
-	default:
-		return nil, nil
-	}
-
-	if err := res.Populate(ctx); err != nil {
-		return nil, errors.Wrap(err, "populating directory resolver")
-	}
-
-	return res, nil
-}
-
-func resolveCollectionPath(
-	ctx context.Context,
-	resolver graph.ContainerResolver,
-	tenantID, user, folderID string,
-	category path.CategoryType,
-) (path.Path, error) {
-	if resolver == nil {
-		// Allows caller to default to old-style path.
-		return nil, errors.WithStack(errNilResolver)
-	}
-
-	p, err := resolver.IDToPath(ctx, folderID)
-	if err != nil {
-		return nil, errors.Wrap(err, "resolving folder ID")
-	}
-
-	return p.ToDataLayerExchangePathForCategory(
-		tenantID,
-		user,
-		category,
-		false,
-	)
-}
-
 // IterateSelectAllDescendablesForCollection utility function for
 // Iterating through MessagesCollectionResponse or ContactsCollectionResponse,
 // objects belonging to any folder are
@@ -99,6 +41,8 @@ func IterateSelectAllDescendablesForCollections(
 		collectionType optionIdentifier
 		category       path.CategoryType
 		resolver       graph.ContainerResolver
+		dirPath        path.Path
+		err            error
 	)
 
 	return func(pageItem any) bool {
@@ -132,34 +76,19 @@ func IterateSelectAllDescendablesForCollections(
 		// Saving to messages to list. Indexed by folder
 		directory := *entry.GetParentFolderId()
 
-		dirPath, err := path.Builder{}.Append(directory).ToDataLayerExchangePathForCategory(
-			qp.Credentials.TenantID,
-			qp.User,
-			category,
-			false,
-		)
-		if err != nil {
-			// This really shouldn't happen unless we have a bad category.
-			errUpdater("converting to resource path", err)
-			return true
-		}
-
 		if _, ok = collections[directory]; !ok {
-			newPath, err := resolveCollectionPath(
+			dirPath, err = getCollectionPath(
 				ctx,
+				qp,
 				resolver,
-				qp.Credentials.TenantID,
-				qp.User,
 				directory,
 				category,
 			)
-
 			if err != nil {
-				if !errors.Is(err, errNilResolver) {
+				errUpdater(
-					errUpdater("", err)
+					"failure during IterateSelectAllDescendablesForCollections",
-				}
+					err,
-			} else {
+				)
-				dirPath = newPath
 			}
 
 			service, err := createService(qp.Credentials, qp.FailFast)
@@ -254,7 +183,7 @@ func IterateSelectAllEventsFromCalendars(
 				false,
 			)
 			if err != nil {
-				// we shouldn't ever hit this error
+				// we should never hit this error
 				errUpdater("converting to resource path", err)
 				return true
 			}
@@ -356,33 +285,20 @@ func IterateFilterFolderDirectoriesForCollections(
 
 		directory := *folder.GetId()
 
-		dirPath, err := path.Builder{}.Append(directory).ToDataLayerExchangePathForCategory(
+		dirPath, err := getCollectionPath(
-			qp.Credentials.TenantID,
-			qp.User,
-			path.EmailCategory,
-			false,
-		)
-		if err != nil {
-			// we shouldn't ever hit this error.
-			errUpdater("converting to resource path", err)
-			return true
-		}
-
-		p, err := resolveCollectionPath(
 			ctx,
+			qp,
 			resolver,
-			qp.Credentials.TenantID,
-			qp.User,
 			directory,
 			path.EmailCategory,
 		)
-
 		if err != nil {
-			if !errors.Is(err, errNilResolver) {
+			errUpdater(
-				errUpdater("", err)
+				"failure converting path during IterateFilterFolderDirectoriesForCollections",
-			}
+				err,
-		} else {
+			)
-			dirPath = p
+
+			return true
 		}
 
 		service, err = createService(qp.Credentials, qp.FailFast)