From e37fde11170c6ee1434d91ef2d78afe445afc14e Mon Sep 17 00:00:00 2001 From: 0x5487 Date: Fri, 20 Feb 2026 11:06:50 +0800 Subject: [PATCH] Refactor filesystem tools to use a `fileReadWriter` interface for both host and sandboxed I/O, improving atomic writes and error handling. --- pkg/tools/edit.go | 206 ++++++++++++++++++---------------- pkg/tools/edit_test.go | 137 +++++++++++++++++++++++ pkg/tools/filesystem.go | 207 +++++++++++++++++++++-------------- pkg/tools/filesystem_test.go | 149 +++++++++++++++++++++++-- 4 files changed, 508 insertions(+), 191 deletions(-) diff --git a/pkg/tools/edit.go b/pkg/tools/edit.go index 1388690ee..aafa2adaf 100644 --- a/pkg/tools/edit.go +++ b/pkg/tools/edit.go @@ -2,8 +2,10 @@ package tools import ( "context" + "errors" "fmt" "io" + "io/fs" "os" "strings" ) @@ -68,77 +70,19 @@ func (t *EditFileTool) Execute(ctx context.Context, args map[string]interface{}) return ErrorResult("new_text is required") } - // If not restricted, perform operations directly - if !t.restrict { - content, err := os.ReadFile(path) - if err != nil { - if os.IsNotExist(err) { - return ErrorResult(fmt.Sprintf("file not found: %s", path)) + if t.restrict { + return executeInRoot(t.allowedDir, path, func(root *os.Root, relPath string) (*ToolResult, error) { + if err := editFileInRoot(root, relPath, oldText, newText); err != nil { + return nil, err } - return ErrorResult(fmt.Sprintf("failed to read file: %v", err)) - } - - contentStr := string(content) - if !strings.Contains(contentStr, oldText) { - return ErrorResult("old_text not found in file. Make sure it matches exactly") - } - - count := strings.Count(contentStr, oldText) - if count > 1 { - return ErrorResult(fmt.Sprintf("old_text appears %d times. Please provide more context to make it unique", count)) - } - - newContent := strings.Replace(contentStr, oldText, newText, 1) - - if err := os.WriteFile(path, []byte(newContent), 0644); err != nil { - return ErrorResult(fmt.Sprintf("failed to write file: %v", err)) - } - - return SilentResult(fmt.Sprintf("File edited: %s", path)) + return SilentResult(fmt.Sprintf("File edited: %s", path)), nil + }) } - // Use executeInRoot to safely access the file - return executeInRoot(t.allowedDir, path, func(root *os.Root, relPath string) (*ToolResult, error) { - f, err := root.Open(relPath) - if err != nil { - if os.IsNotExist(err) { - return nil, fmt.Errorf("file not found: %s", path) - } - return nil, fmt.Errorf("failed to open file: %w", err) - } - - content, err := io.ReadAll(f) - f.Close() - - if err != nil { - return nil, fmt.Errorf("failed to read file: %v", err) - } - - contentStr := string(content) - - if !strings.Contains(contentStr, oldText) { - return nil, fmt.Errorf("old_text not found in file. Make sure it matches exactly") - } - - count := strings.Count(contentStr, oldText) - if count > 1 { - return nil, fmt.Errorf("old_text appears %d times. Please provide more context to make it unique", count) - } - - newContent := strings.Replace(contentStr, oldText, newText, 1) - - fw, err := root.Create(relPath) - if err != nil { - return nil, fmt.Errorf("failed to create file for writing: %w", err) - } - defer fw.Close() - - if _, err := fw.Write([]byte(newContent)); err != nil { - return nil, fmt.Errorf("failed to write file: %v", err) - } - - return SilentResult(fmt.Sprintf("File edited: %s", path)), nil - }) + if err := editFile(&hostRW{}, path, oldText, newText); err != nil { + return ErrorResult(err.Error()) + } + return SilentResult(fmt.Sprintf("File edited: %s", path)) } type AppendFileTool struct { @@ -181,38 +125,108 @@ func (t *AppendFileTool) Execute(ctx context.Context, args map[string]interface{ return ErrorResult("path is required") } - content, ok := args["content"].(string) + appendContent, ok := args["content"].(string) if !ok { return ErrorResult("content is required") } - // If not restricted, perform operations directly - if !t.restrict { - f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644) - if err != nil { - return ErrorResult(fmt.Sprintf("failed to open file: %v", err)) - } - defer f.Close() - - if _, err := f.WriteString(content); err != nil { - return ErrorResult(fmt.Sprintf("failed to append to file: %v", err)) - } - - return SilentResult(fmt.Sprintf("Appended to %s", path)) + var rw fileReadWriter + if t.restrict { + return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { + if err := appendFileWithRW(&rootRW{root: root}, relPath, appendContent); err != nil { + return nil, err + } + return SilentResult(fmt.Sprintf("Appended to %s", path)), nil + }) } - // Use executeInRoot to safely access the file - return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { - f, err := root.OpenFile(relPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644) - if err != nil { - return nil, fmt.Errorf("failed to open file: %w", err) - } - defer f.Close() - - if _, err := f.WriteString(content); err != nil { - return nil, fmt.Errorf("failed to append to file: %w", err) - } - - return SilentResult(fmt.Sprintf("Appended to %s", path)), nil - }) + rw = &hostRW{} + if err := appendFileWithRW(rw, path, appendContent); err != nil { + return ErrorResult(err.Error()) + } + return SilentResult(fmt.Sprintf("Appended to %s", path)) +} + +// editFile reads the file via rw, performs the replacement, and writes back. +// It uses a fileReadWriter, allowing the same logic for both restricted and unrestricted modes. +func editFile(rw fileReadWriter, path, oldText, newText string) error { + content, err := rw.Read(path) + if err != nil { + return err + } + + newContent, err := replaceEditContent(content, oldText, newText) + if err != nil { + return err + } + + return rw.Write(path, newContent) +} + +// editFileInRoot performs an in-place edit within an os.Root using a single open call. +// By opening with O_RDWR and reusing the same file descriptor for both read and write, +// we narrow the TOCTOU window compared to two separate open calls. +func editFileInRoot(root *os.Root, relPath, oldText, newText string) error { + f, err := root.OpenFile(relPath, os.O_RDWR, 0) + if err != nil { + if os.IsNotExist(err) { + return fmt.Errorf("failed to read file: file not found: %w", err) + } + if os.IsPermission(err) || strings.Contains(err.Error(), "escapes from parent") { + return fmt.Errorf("failed to read file: access denied: %w", err) + } + return fmt.Errorf("failed to open file for editing: %w", err) + } + defer f.Close() + + content, err := io.ReadAll(f) + if err != nil { + return fmt.Errorf("failed to read file content: %w", err) + } + + newContent, err := replaceEditContent(content, oldText, newText) + if err != nil { + return err + } + + // Truncate the file and seek back to the beginning before writing. + if err := f.Truncate(0); err != nil { + return fmt.Errorf("failed to truncate file for in-place edit: %w", err) + } + if _, err := f.Seek(0, io.SeekStart); err != nil { + return fmt.Errorf("failed to seek to beginning of file: %w", err) + } + + if _, err := f.Write(newContent); err != nil { + return fmt.Errorf("failed to write edited content: %w", err) + } + return nil +} + +// appendFileWithRW reads the existing content (if any) via rw, appends new content, and writes back. +func appendFileWithRW(rw fileReadWriter, path, appendContent string) error { + content, err := rw.Read(path) + if err != nil && !errors.Is(err, fs.ErrNotExist) { + return err + } + + newContent := append(content, []byte(appendContent)...) + return rw.Write(path, newContent) +} + +// replaceEditContent handles the core logic of finding and replacing a single occurrence of oldText. +func replaceEditContent(content []byte, oldText, newText string) ([]byte, error) { + contentStr := string(content) + + if !strings.Contains(contentStr, oldText) { + return nil, fmt.Errorf("old_text not found in file. Make sure it matches exactly") + } + + count := strings.Count(contentStr, oldText) + if count > 1 { + return nil, fmt.Errorf("old_text appears %d times. Please provide more context to make it unique", count) + } + + newContent := strings.Replace(contentStr, oldText, newText, 1) + return []byte(newContent), nil } diff --git a/pkg/tools/edit_test.go b/pkg/tools/edit_test.go index 4855c3f83..8897512ab 100644 --- a/pkg/tools/edit_test.go +++ b/pkg/tools/edit_test.go @@ -288,3 +288,140 @@ func TestEditTool_AppendFile_MissingContent(t *testing.T) { t.Errorf("Expected error when content is missing") } } + +// TestReplaceEditContent verifies the helper function replaceEditContent +func TestReplaceEditContent(t *testing.T) { + tests := []struct { + name string + content []byte + oldText string + newText string + expected []byte + expectError bool + }{ + { + name: "successful replacement", + content: []byte("hello world"), + oldText: "world", + newText: "universe", + expected: []byte("hello universe"), + expectError: false, + }, + { + name: "old text not found", + content: []byte("hello world"), + oldText: "golang", + newText: "rust", + expected: nil, + expectError: true, + }, + { + name: "multiple matches found", + content: []byte("test text test"), + oldText: "test", + newText: "done", + expected: nil, + expectError: true, + }, + } + + for _, tt := range tests { + t.Run(tt.name, func(t *testing.T) { + result, err := replaceEditContent(tt.content, tt.oldText, tt.newText) + if tt.expectError { + assert.Error(t, err) + } else { + assert.NoError(t, err) + assert.Equal(t, tt.expected, result) + } + }) + } +} + +// TestAppendFileTool_AppendToNonExistent_Restricted verifies that AppendFileTool in restricted mode +// can append to a file that does not yet exist — it should silently create the file. +// This exercises the errors.Is(err, fs.ErrNotExist) path in appendFileWithRW + rootRW. +func TestAppendFileTool_AppendToNonExistent_Restricted(t *testing.T) { + workspace := t.TempDir() + tool := NewAppendFileTool(workspace, true) + ctx := context.Background() + + args := map[string]interface{}{ + "path": "brand_new_file.txt", + "content": "first content", + } + + result := tool.Execute(ctx, args) + assert.False(t, result.IsError, "Expected success when appending to non-existent file in restricted mode, got: %s", result.ForLLM) + + // Verify the file was created with correct content + data, err := os.ReadFile(filepath.Join(workspace, "brand_new_file.txt")) + assert.NoError(t, err) + assert.Equal(t, "first content", string(data)) +} + +// TestAppendFileTool_Restricted_Success verifies that AppendFileTool in restricted mode +// correctly appends to an existing file within the sandbox. +func TestAppendFileTool_Restricted_Success(t *testing.T) { + workspace := t.TempDir() + testFile := "existing.txt" + err := os.WriteFile(filepath.Join(workspace, testFile), []byte("initial"), 0644) + assert.NoError(t, err) + + tool := NewAppendFileTool(workspace, true) + ctx := context.Background() + args := map[string]interface{}{ + "path": testFile, + "content": " appended", + } + + result := tool.Execute(ctx, args) + assert.False(t, result.IsError, "Expected success, got: %s", result.ForLLM) + assert.True(t, result.Silent) + + data, err := os.ReadFile(filepath.Join(workspace, testFile)) + assert.NoError(t, err) + assert.Equal(t, "initial appended", string(data)) +} + +// TestEditFileTool_Restricted_InPlaceEdit verifies that EditFileTool in restricted mode +// correctly edits a file using the single-open editFileInRoot path. +func TestEditFileTool_Restricted_InPlaceEdit(t *testing.T) { + workspace := t.TempDir() + testFile := "edit_target.txt" + err := os.WriteFile(filepath.Join(workspace, testFile), []byte("Hello World"), 0644) + assert.NoError(t, err) + + tool := NewEditFileTool(workspace, true) + ctx := context.Background() + args := map[string]interface{}{ + "path": testFile, + "old_text": "World", + "new_text": "Go", + } + + result := tool.Execute(ctx, args) + assert.False(t, result.IsError, "Expected success, got: %s", result.ForLLM) + assert.True(t, result.Silent) + + data, err := os.ReadFile(filepath.Join(workspace, testFile)) + assert.NoError(t, err) + assert.Equal(t, "Hello Go", string(data)) +} + +// TestEditFileTool_Restricted_FileNotFound verifies that editFileInRoot returns a proper +// error message when the target file does not exist. +func TestEditFileTool_Restricted_FileNotFound(t *testing.T) { + workspace := t.TempDir() + tool := NewEditFileTool(workspace, true) + ctx := context.Background() + args := map[string]interface{}{ + "path": "no_such_file.txt", + "old_text": "old", + "new_text": "new", + } + + result := tool.Execute(ctx, args) + assert.True(t, result.IsError) + assert.Contains(t, result.ForLLM, "not found") +} diff --git a/pkg/tools/filesystem.go b/pkg/tools/filesystem.go index 77b0b91b6..507ffbd42 100644 --- a/pkg/tools/filesystem.go +++ b/pkg/tools/filesystem.go @@ -3,10 +3,10 @@ package tools import ( "context" "fmt" - "io" "os" "path/filepath" "strings" + "time" ) type ReadFileTool struct { @@ -45,31 +45,21 @@ func (t *ReadFileTool) Execute(ctx context.Context, args map[string]interface{}) return ErrorResult("path is required") } - // If restriction is disabled, fall back to standard os interactions (insecure but intended) - if !t.restrict { - content, err := os.ReadFile(path) - if err != nil { - return ErrorResult(fmt.Sprintf("failed to read file: %v", err)) - } - return NewToolResult(string(content)) + if t.restrict { + return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { + content, err := (&rootRW{root: root}).Read(relPath) + if err != nil { + return nil, err + } + return NewToolResult(string(content)), nil + }) } - return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { - f, err := root.Open(relPath) - if err != nil { - if os.IsNotExist(err) { - return nil, fmt.Errorf("failed to read file: file not found: %s", path) - } - return nil, fmt.Errorf("access denied or failed to open: %w", err) - } - defer f.Close() - - content, err := io.ReadAll(f) - if err != nil { - return nil, fmt.Errorf("failed to read file: %v", err) - } - return NewToolResult(string(content)), nil - }) + content, err := (&hostRW{}).Read(path) + if err != nil { + return ErrorResult(err.Error()) + } + return NewToolResult(string(content)) } type WriteFileTool struct { @@ -117,37 +107,20 @@ func (t *WriteFileTool) Execute(ctx context.Context, args map[string]interface{} return ErrorResult("content is required") } - if !t.restrict { - if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil { - return ErrorResult(fmt.Sprintf("failed to create directory: %v", err)) - } - if err := os.WriteFile(path, []byte(content), 0644); err != nil { - return ErrorResult(fmt.Sprintf("failed to write file: %v", err)) - } - return SilentResult(fmt.Sprintf("File written: %s", path)) + if t.restrict { + return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { + if err := (&rootRW{root: root}).Write(relPath, []byte(content)); err != nil { + return nil, err + } + return SilentResult(fmt.Sprintf("File written: %s", path)), nil + }) } - return executeInRoot(t.workspace, path, func(root *os.Root, relPath string) (*ToolResult, error) { - // Ensure parent directory exists within root using recursive creation - dir := filepath.Dir(relPath) - if dir != "." && dir != "/" { - if err := mkdirAllInRoot(root, dir); err != nil { - return nil, fmt.Errorf("failed to create parent directories: %w", err) - } - } + if err := (&hostRW{}).Write(path, []byte(content)); err != nil { + return ErrorResult(err.Error()) + } - f, err := root.Create(relPath) - if err != nil { - return nil, fmt.Errorf("failed to create file: %w", err) - } - defer f.Close() - - _, err = f.WriteString(content) - if err != nil { - return nil, fmt.Errorf("failed to write file: %w", err) - } - return SilentResult(fmt.Sprintf("File written: %s", path)), nil - }) + return SilentResult(fmt.Sprintf("File written: %s", path)) } type ListDirTool struct { @@ -222,6 +195,102 @@ func formatDirEntries(entries []os.DirEntry) *ToolResult { return NewToolResult(result.String()) } +// fileReadWriter abstracts reading and writing files, allowing both unrestricted +// (host filesystem) and sandbox (os.Root) implementations to share the same logic. +type fileReadWriter interface { + Read(path string) ([]byte, error) + Write(path string, data []byte) error +} + +// hostRW is an unrestricted fileReadWriter that operates directly on the host filesystem. +type hostRW struct{} + +func (h *hostRW) Read(path string) ([]byte, error) { + content, err := os.ReadFile(path) + if err != nil { + if os.IsNotExist(err) { + return nil, fmt.Errorf("failed to read file: file not found: %w", err) + } + if os.IsPermission(err) { + return nil, fmt.Errorf("failed to read file: access denied: %w", err) + } + return nil, fmt.Errorf("failed to read file: %w", err) + } + return content, nil +} + +func (h *hostRW) Write(path string, data []byte) error { + dir := filepath.Dir(path) + if err := os.MkdirAll(dir, 0755); err != nil { + return fmt.Errorf("failed to create parent directories: %w", err) + } + + tmpPath := fmt.Sprintf("%s.%d.tmp", path, time.Now().UnixNano()) + if err := os.WriteFile(tmpPath, data, 0644); err != nil { + return fmt.Errorf("failed to write temp file: %w", err) + } + + if err := os.Rename(tmpPath, path); err != nil { + os.Remove(tmpPath) + return fmt.Errorf("failed to replace original file: %w", err) + } + return nil +} + +// rootRW is a sandboxed fileReadWriter that operates within an os.Root boundary. +// All paths passed to Read/Write must be relative to the root. +type rootRW struct { + root *os.Root +} + +func (r *rootRW) Read(path string) ([]byte, error) { + content, err := r.root.ReadFile(path) + if err != nil { + if os.IsNotExist(err) { + return nil, fmt.Errorf("failed to read file: file not found: %w", err) + } + // os.Root returns "escapes from parent" for paths outside the root + if os.IsPermission(err) || strings.Contains(err.Error(), "escapes from parent") || strings.Contains(err.Error(), "permission denied") { + return nil, fmt.Errorf("failed to read file: access denied: %w", err) + } + return nil, fmt.Errorf("failed to read file: %w", err) + } + return content, nil +} + +func (r *rootRW) Write(path string, data []byte) error { + dir := filepath.Dir(path) + if dir != "." && dir != "/" { + // Use native root.MkdirAll which handles the "file exists at path" check internally. + if err := r.root.MkdirAll(dir, 0755); err != nil { + return fmt.Errorf("failed to create parent directories: %w", err) + } + } + + tmpRelPath := fmt.Sprintf("%s.%d.tmp", path, time.Now().UnixNano()) + fw, err := r.root.Create(tmpRelPath) + if err != nil { + return fmt.Errorf("failed to create temp file for writing: %w", err) + } + + if _, err := fw.Write(data); err != nil { + fw.Close() + r.root.Remove(tmpRelPath) + return fmt.Errorf("failed to write to temp file: %w", err) + } + + if err := fw.Close(); err != nil { + r.root.Remove(tmpRelPath) + return fmt.Errorf("failed to close temp file: %w", err) + } + + if err := r.root.Rename(tmpRelPath, path); err != nil { + r.root.Remove(tmpRelPath) + return fmt.Errorf("failed to rename temp file over target: %w", err) + } + return nil +} + // Helper to get a safe relative path for os.Root usage func getSafeRelPath(workspace, path string) (string, error) { if workspace == "" { @@ -240,7 +309,7 @@ func getSafeRelPath(workspace, path string) (string, error) { path = rel } - // Check for escape + // Check for escape manually (defense-in-depth, as os.Root also rejects paths that escape the root) if path == ".." || strings.HasPrefix(path, "../") { return "", fmt.Errorf("path escapes workspace: %s", path) } @@ -275,35 +344,3 @@ func executeInRoot(workspace string, path string, fn func(root *os.Root, relPath return result } - -// mkdirAllInRoot mimics os.MkdirAll but within os.Root -func mkdirAllInRoot(root *os.Root, relPath string) error { - relPath = filepath.Clean(relPath) - if relPath == "." || relPath == "/" { - return nil - } - - dir := filepath.Dir(relPath) - if dir != "." && dir != "/" { - if err := mkdirAllInRoot(root, dir); err != nil { - return err - } - } - - err := root.Mkdir(relPath, 0755) - if err != nil { - if os.IsExist(err) { - // Check if it's a directory - st, statErr := root.Stat(relPath) - if statErr != nil { - return statErr - } - if !st.IsDir() { - return fmt.Errorf("%s: not a directory", relPath) - } - return nil - } - return err - } - return nil -} diff --git a/pkg/tools/filesystem_test.go b/pkg/tools/filesystem_test.go index d6f8b747a..635bf009f 100644 --- a/pkg/tools/filesystem_test.go +++ b/pkg/tools/filesystem_test.go @@ -2,6 +2,7 @@ package tools import ( "context" + "io" "os" "path/filepath" "strings" @@ -304,7 +305,9 @@ func TestFilesystemTool_EmptyWorkspace_AccessDenied(t *testing.T) { assert.Contains(t, result.ForLLM, "workspace is not defined", "Expected 'workspace is not defined' error") } -func TestMkdirAllInRoot(t *testing.T) { +// TestRootMkdirAll verifies that root.MkdirAll (used by atomicWriteFileInRoot) handles all cases: +// single dir, deeply nested dirs, already-existing dirs, and a file blocking a directory path. +func TestRootMkdirAll(t *testing.T) { workspace := t.TempDir() root, err := os.OpenRoot(workspace) if err != nil { @@ -312,27 +315,27 @@ func TestMkdirAllInRoot(t *testing.T) { } defer root.Close() - // Test case 1: Single directory - err = mkdirAllInRoot(root, "dir1") + // Case 1: Single directory + err = root.MkdirAll("dir1", 0755) assert.NoError(t, err) _, err = os.Stat(filepath.Join(workspace, "dir1")) assert.NoError(t, err) - // Test case 2: Deeply nested directory - err = mkdirAllInRoot(root, "a/b/c/d") + // Case 2: Deeply nested directory + err = root.MkdirAll("a/b/c/d", 0755) assert.NoError(t, err) _, err = os.Stat(filepath.Join(workspace, "a/b/c/d")) assert.NoError(t, err) - // Test case 3: Already exists - err = mkdirAllInRoot(root, "a/b/c/d") + // Case 3: Already exists — must be idempotent + err = root.MkdirAll("a/b/c/d", 0755) assert.NoError(t, err) - // Test case 4: File exists with same name (should fail) + // Case 4: A regular file blocks directory creation — must error err = os.WriteFile(filepath.Join(workspace, "file_exists"), []byte("data"), 0644) assert.NoError(t, err) - err = mkdirAllInRoot(root, "file_exists") - assert.Error(t, err) + err = root.MkdirAll("file_exists", 0755) + assert.Error(t, err, "expected error when a file exists at the directory path") } func TestFilesystemTool_WriteFile_Restricted_CreateDir(t *testing.T) { @@ -356,3 +359,129 @@ func TestFilesystemTool_WriteFile_Restricted_CreateDir(t *testing.T) { assert.NoError(t, err) assert.Equal(t, content, string(data)) } + +// TestHostRW_Read_PermissionDenied verifies that hostRW.Read surfaces access denied errors. +func TestHostRW_Read_PermissionDenied(t *testing.T) { + if os.Getuid() == 0 { + t.Skip("skipping permission test: running as root") + } + tmpDir := t.TempDir() + protected := filepath.Join(tmpDir, "protected.txt") + err := os.WriteFile(protected, []byte("secret"), 0000) + assert.NoError(t, err) + defer os.Chmod(protected, 0644) // ensure cleanup + + _, err = (&hostRW{}).Read(protected) + assert.Error(t, err) + assert.Contains(t, err.Error(), "access denied") +} + +// TestHostRW_Read_Directory verifies that hostRW.Read returns an error when given a directory path. +func TestHostRW_Read_Directory(t *testing.T) { + tmpDir := t.TempDir() + + _, err := (&hostRW{}).Read(tmpDir) + assert.Error(t, err, "expected error when reading a directory as a file") +} + +// TestRootRW_Read_Directory verifies that rootRW.Read returns an error when given a directory. +func TestRootRW_Read_Directory(t *testing.T) { + workspace := t.TempDir() + root, err := os.OpenRoot(workspace) + assert.NoError(t, err) + defer root.Close() + + // Create a subdirectory + err = root.Mkdir("subdir", 0755) + assert.NoError(t, err) + + _, err = (&rootRW{root: root}).Read("subdir") + assert.Error(t, err, "expected error when reading a directory as a file") +} + +// TestHostRW_Write_ParentDirMissing verifies that hostRW.Write creates parent dirs automatically. +func TestHostRW_Write_ParentDirMissing(t *testing.T) { + tmpDir := t.TempDir() + target := filepath.Join(tmpDir, "a", "b", "c", "file.txt") + + err := (&hostRW{}).Write(target, []byte("hello")) + assert.NoError(t, err) + + data, err := os.ReadFile(target) + assert.NoError(t, err) + assert.Equal(t, "hello", string(data)) +} + +// TestRootRW_Write_ParentDirMissing verifies that rootRW.Write creates +// nested parent directories automatically within the sandbox. +func TestRootRW_Write_ParentDirMissing(t *testing.T) { + workspace := t.TempDir() + root, err := os.OpenRoot(workspace) + assert.NoError(t, err) + defer root.Close() + + relPath := "x/y/z/file.txt" + err = (&rootRW{root: root}).Write(relPath, []byte("nested")) + assert.NoError(t, err) + + data, err := os.ReadFile(filepath.Join(workspace, relPath)) + assert.NoError(t, err) + assert.Equal(t, "nested", string(data)) +} + +// TestHostRW_Write verifies the hostRW.Write helper function +func TestHostRW_Write(t *testing.T) { + tmpDir := t.TempDir() + testFile := filepath.Join(tmpDir, "atomic_test.txt") + testData := []byte("atomic test content") + + err := (&hostRW{}).Write(testFile, testData) + assert.NoError(t, err) + + content, err := os.ReadFile(testFile) + assert.NoError(t, err) + assert.Equal(t, testData, content) + + // Verify it overwrites correctly + newData := []byte("new atomic content") + err = (&hostRW{}).Write(testFile, newData) + assert.NoError(t, err) + + content, err = os.ReadFile(testFile) + assert.NoError(t, err) + assert.Equal(t, newData, content) +} + +// TestRootRW_Write verifies the rootRW.Write helper function +func TestRootRW_Write(t *testing.T) { + tmpDir := t.TempDir() + root, err := os.OpenRoot(tmpDir) + assert.NoError(t, err) + defer root.Close() + + relPath := "atomic_root_test.txt" + testData := []byte("atomic root test content") + + erw := &rootRW{root: root} + err = erw.Write(relPath, testData) + assert.NoError(t, err) + + f, err := root.Open(relPath) + assert.NoError(t, err) + content, err := io.ReadAll(f) + assert.NoError(t, err) + f.Close() + assert.Equal(t, testData, content) + + // Verify it overwrites correctly + newData := []byte("new root atomic content") + err = erw.Write(relPath, newData) + assert.NoError(t, err) + + f, err = root.Open(relPath) + assert.NoError(t, err) + content, err = io.ReadAll(f) + assert.NoError(t, err) + f.Close() + assert.Equal(t, newData, content) +}