Add workspace filesystem helpers

internal/core/workspace/files_test.go

@@ -0,0 +1,148 @@
+package workspace
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestSafePathAcceptsCleanRelativePaths(t *testing.T) {
+	root := t.TempDir()
+
+	got, err := SafePath(root, "source/manifest.json")
+	if err != nil {
+		t.Fatalf("SafePath: %v", err)
+	}
+
+	want := filepath.Join(root, "source", "manifest.json")
+	if got != want {
+		t.Fatalf("SafePath = %q, want %q", got, want)
+	}
+}
+
+func TestSafePathRejectsUnsafeNames(t *testing.T) {
+	root := t.TempDir()
+	tests := []struct {
+		name string
+		path string
+		want string
+	}{
+		{name: "empty", path: " ", want: "empty"},
+		{name: "absolute", path: filepath.Join(root, "artifact.json"), want: "relative"},
+		{name: "parent segment", path: "../artifact.json", want: ".."},
+		{name: "embedded parent", path: "source/../artifact.json", want: ".."},
+		{name: "backslash", path: `source\artifact.json`, want: "slash-separated"},
+		{name: "unclean", path: "source//artifact.json", want: "clean"},
+		{name: "dot", path: ".", want: ".."},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got, err := SafePath(root, tc.path)
+			if err == nil {
+				t.Fatalf("SafePath returned %q, want error", got)
+			}
+			if !strings.Contains(err.Error(), tc.want) {
+				t.Fatalf("SafePath error = %v, want containing %q", err, tc.want)
+			}
+		})
+	}
+}
+
+func TestSafePathRejectsEmptyRoot(t *testing.T) {
+	got, err := SafePath(" ", "artifact.json")
+	if err == nil {
+		t.Fatalf("SafePath returned %q, want error", got)
+	}
+	if !strings.Contains(err.Error(), "root") {
+		t.Fatalf("SafePath error = %v, want root error", err)
+	}
+}
+
+func TestSafePathDoesNotPermitEscapingRoot(t *testing.T) {
+	root := t.TempDir()
+	for _, name := range []string{
+		"..",
+		"../outside.json",
+		"nested/../../outside.json",
+	} {
+		t.Run(name, func(t *testing.T) {
+			got, err := SafePath(root, name)
+			if err == nil {
+				t.Fatalf("SafePath returned %q, want error", got)
+			}
+		})
+	}
+}
+
+func TestWriteJSONWritesIndentedAtomicArtifact(t *testing.T) {
+	root := t.TempDir()
+
+	err := WriteJSON(root, "source/manifest.json", map[string]any{
+		"status": "succeeded",
+		"count":  2,
+	})
+	if err != nil {
+		t.Fatalf("WriteJSON: %v", err)
+	}
+
+	got := string(readFile(t, filepath.Join(root, "source", "manifest.json")))
+	if !strings.HasSuffix(got, "\n") {
+		t.Fatalf("expected trailing newline, got %q", got)
+	}
+	if !strings.Contains(got, `"status": "succeeded"`) || !strings.Contains(got, `"count": 2`) {
+		t.Fatalf("unexpected JSON: %s", got)
+	}
+	assertNoTempFiles(t, filepath.Join(root, "source"))
+}
+
+func TestWriteBytesWritesNestedArtifact(t *testing.T) {
+	root := t.TempDir()
+
+	if err := WriteBytes(root, "chunk/chunks.json", []byte("payload")); err != nil {
+		t.Fatalf("WriteBytes: %v", err)
+	}
+
+	got := string(readFile(t, filepath.Join(root, "chunk", "chunks.json")))
+	if got != "payload" {
+		t.Fatalf("bytes = %q, want payload", got)
+	}
+	assertNoTempFiles(t, filepath.Join(root, "chunk"))
+}
+
+func TestWritersRejectUnsafePaths(t *testing.T) {
+	root := t.TempDir()
+
+	if err := WriteBytes(root, "../outside.json", []byte("payload")); err == nil {
+		t.Fatalf("WriteBytes accepted unsafe path")
+	}
+	if err := WriteJSON(root, `debug\trace.json`, map[string]string{"x": "y"}); err == nil {
+		t.Fatalf("WriteJSON accepted unsafe path")
+	}
+	if _, err := os.Stat(filepath.Join(root, "..", "outside.json")); !os.IsNotExist(err) {
+		t.Fatalf("outside path stat err = %v, want not exist", err)
+	}
+}
+
+func readFile(t *testing.T, path string) []byte {
+	t.Helper()
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("read %q: %v", path, err)
+	}
+	return data
+}
+
+func assertNoTempFiles(t *testing.T, dir string) {
+	t.Helper()
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		t.Fatalf("read dir %q: %v", dir, err)
+	}
+	for _, entry := range entries {
+		if strings.Contains(entry.Name(), ".tmp-") {
+			t.Fatalf("temporary file was not cleaned up: %s", entry.Name())
+		}
+	}
+}