diff --git a/internal/lsp/cache/snapshot.go b/internal/lsp/cache/snapshot.go
index c96ad69..d141c51 100644
--- a/internal/lsp/cache/snapshot.go
+++ b/internal/lsp/cache/snapshot.go
@@ -791,12 +791,12 @@
 	return s.files[f.URI()]
 }
 
-// GetFile returns a File for the given URI. If the file is unknown it is added
-// to the managed set.
+// GetVersionedFile returns a File for the given URI. If the file is unknown it
+// is added to the managed set.
 //
 // GetFile succeeds even if the file does not exist. A non-nil error return
 // indicates some type of internal error, for example if ctx is cancelled.
-func (s *snapshot) GetFile(ctx context.Context, uri span.URI) (source.VersionedFileHandle, error) {
+func (s *snapshot) GetVersionedFile(ctx context.Context, uri span.URI) (source.VersionedFileHandle, error) {
 	f, err := s.view.getFile(uri)
 	if err != nil {
 		return nil, err
@@ -807,6 +807,11 @@
 	return s.getFileLocked(ctx, f)
 }
 
+// GetFile implements the fileSource interface by wrapping GetVersionedFile.
+func (s *snapshot) GetFile(ctx context.Context, uri span.URI) (source.FileHandle, error) {
+	return s.GetVersionedFile(ctx, uri)
+}
+
 func (s *snapshot) getFileLocked(ctx context.Context, f *fileBase) (source.VersionedFileHandle, error) {
 	if fh, ok := s.files[f.URI()]; ok {
 		return fh, nil
diff --git a/internal/lsp/code_action.go b/internal/lsp/code_action.go
index 20e9f99..cb45045 100644
--- a/internal/lsp/code_action.go
+++ b/internal/lsp/code_action.go
@@ -282,7 +282,7 @@
 				Edit:        protocol.WorkspaceEdit{},
 			}
 			for uri, edits := range fix.Edits {
-				fh, err := snapshot.GetFile(ctx, uri)
+				fh, err := snapshot.GetVersionedFile(ctx, uri)
 				if err != nil {
 					return nil, nil, err
 				}
@@ -481,7 +481,7 @@
 			return nil, nil
 		}
 		var err error
-		modFH, err = snapshot.GetFile(ctx, modURI)
+		modFH, err = snapshot.GetVersionedFile(ctx, modURI)
 		if err != nil {
 			return nil, err
 		}
diff --git a/internal/lsp/diagnostics.go b/internal/lsp/diagnostics.go
index f3e59c6..7469a36 100644
--- a/internal/lsp/diagnostics.go
+++ b/internal/lsp/diagnostics.go
@@ -337,7 +337,7 @@
 			Severity: protocol.SeverityError,
 			Source:   e.Category,
 		}
-		fh, err := snapshot.GetFile(ctx, e.URI)
+		fh, err := snapshot.GetVersionedFile(ctx, e.URI)
 		if err != nil {
 			return err
 		}
diff --git a/internal/lsp/general.go b/internal/lsp/general.go
index ff76d58..307660b 100644
--- a/internal/lsp/general.go
+++ b/internal/lsp/general.go
@@ -470,7 +470,7 @@
 		return nil, nil, false, func() {}, err
 	}
 	snapshot, release := view.Snapshot(ctx)
-	fh, err := snapshot.GetFile(ctx, uri)
+	fh, err := snapshot.GetVersionedFile(ctx, uri)
 	if err != nil {
 		release()
 		return nil, nil, false, func() {}, err
diff --git a/internal/lsp/lsp_test.go b/internal/lsp/lsp_test.go
index b24b436..d94b8f0 100644
--- a/internal/lsp/lsp_test.go
+++ b/internal/lsp/lsp_test.go
@@ -467,7 +467,7 @@
 	snapshot, release := view.Snapshot(r.ctx)
 	defer release()
 
-	fh, err := snapshot.GetFile(r.ctx, uri)
+	fh, err := snapshot.GetVersionedFile(r.ctx, uri)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -577,7 +577,7 @@
 	snapshot, release := view.Snapshot(r.ctx)
 	defer release()
 
-	fh, err := snapshot.GetFile(r.ctx, uri)
+	fh, err := snapshot.GetVersionedFile(r.ctx, uri)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/internal/lsp/mod/diagnostics.go b/internal/lsp/mod/diagnostics.go
index e8c4533..8904ba2 100644
--- a/internal/lsp/mod/diagnostics.go
+++ b/internal/lsp/mod/diagnostics.go
@@ -21,7 +21,7 @@
 
 	reports := map[source.VersionedFileIdentity][]*source.Diagnostic{}
 	for _, uri := range snapshot.ModFiles() {
-		fh, err := snapshot.GetFile(ctx, uri)
+		fh, err := snapshot.GetVersionedFile(ctx, uri)
 		if err != nil {
 			return nil, err
 		}
@@ -44,7 +44,7 @@
 			} else {
 				diag.Severity = protocol.SeverityWarning
 			}
-			fh, err := snapshot.GetFile(ctx, e.URI)
+			fh, err := snapshot.GetVersionedFile(ctx, e.URI)
 			if err != nil {
 				return nil, err
 			}
diff --git a/internal/lsp/rename.go b/internal/lsp/rename.go
index cb364a1..cef0638 100644
--- a/internal/lsp/rename.go
+++ b/internal/lsp/rename.go
@@ -24,7 +24,7 @@
 
 	var docChanges []protocol.TextDocumentEdit
 	for uri, e := range edits {
-		fh, err := snapshot.GetFile(ctx, uri)
+		fh, err := snapshot.GetVersionedFile(ctx, uri)
 		if err != nil {
 			return nil, err
 		}
diff --git a/internal/lsp/source/diagnostics.go b/internal/lsp/source/diagnostics.go
index c1f5826..2f0e7d6 100644
--- a/internal/lsp/source/diagnostics.go
+++ b/internal/lsp/source/diagnostics.go
@@ -128,7 +128,7 @@
 }
 
 func FileDiagnostics(ctx context.Context, snapshot Snapshot, uri span.URI) (VersionedFileIdentity, []*Diagnostic, error) {
-	fh, err := snapshot.GetFile(ctx, uri)
+	fh, err := snapshot.GetVersionedFile(ctx, uri)
 	if err != nil {
 		return VersionedFileIdentity{}, nil, err
 	}
diff --git a/internal/lsp/source/view.go b/internal/lsp/source/view.go
index 291dfe3..c84ff06 100644
--- a/internal/lsp/source/view.go
+++ b/internal/lsp/source/view.go
@@ -44,9 +44,13 @@
 	// in the given snapshot.
 	FindFile(uri span.URI) VersionedFileHandle
 
-	// GetFile returns the FileHandle for a given URI, initializing it
-	// if it is not already part of the snapshot.
-	GetFile(ctx context.Context, uri span.URI) (VersionedFileHandle, error)
+	// GetVersionedFile returns the VersionedFileHandle for a given URI,
+	// initializing it if it is not already part of the snapshot.
+	GetVersionedFile(ctx context.Context, uri span.URI) (VersionedFileHandle, error)
+
+	// GetFile returns the FileHandle for a given URI, initializing it if it is
+	// not already part of the snapshot.
+	GetFile(ctx context.Context, uri span.URI) (FileHandle, error)
 
 	// AwaitInitialized waits until the snapshot's view is initialized.
 	AwaitInitialized(ctx context.Context)
@@ -203,6 +207,14 @@
 	IsGoPrivatePath(path string) bool
 }
 
+// A FileSource maps uris to FileHandles. This abstraction exists both for
+// testability, and so that algorithms can be run equally on session and
+// snapshot files.
+type FileSource interface {
+	// GetFile returns the FileHandle for a given URI.
+	GetFile(ctx context.Context, uri span.URI) (FileHandle, error)
+}
+
 type BuiltinPackage struct {
 	Package    *ast.Package
 	ParsedFile *ParsedGoFile