fix(serve): opening a project whose folder is gone is refused with workspace.folder_missing and the path, not the system's stat sentence

internal/frontend/serve/terminals_test.go

@@ -4,8 +4,10 @@ import (
 	"bufio"
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
+	"path/filepath"
 	"reasonix/internal/base/testenv"
 	"runtime"
 	"strings"
@@ -188,3 +190,14 @@ func TestARemotePanesTerminalsAreForwardedForTheHostAndNeverForADevice(t *testin
 		t.Fatalf("the host's request was forwarded %d times, want once", len(rk.cookies))
 	}
 }
+
+func TestAMissingProjectFolderIsRefusedByCodeNotByTheSystemsSentence(t *testing.T) {
+	_, err := resolveWorkspaceDir(filepath.Join(t.TempDir(), "gone", "worktree"))
+	var c *coded
+	if !errors.As(err, &c) || c.reason.Code != codeWorkspaceMissing || c.status != http.StatusBadRequest {
+		t.Fatalf("a folder that is not there = %v, want a %s refusal with 400", err, codeWorkspaceMissing)
+	}
+	if c.reason.Params["path"] == "" {
+		t.Fatal("the refusal must carry the path so the page can say which folder")
+	}
+}

internal/frontend/serve/workspace.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io/fs"
 	"log/slog"
 	"net/http"
 	"os"
@@ -149,11 +150,14 @@ func resolveWorkspaceDir(dir string) (string, error) {
 		return "", err
 	}
 	info, err := os.Stat(abs)
+	if errors.Is(err, fs.ErrNotExist) {
+		return "", refusal(http.StatusBadRequest, codeWorkspaceMissing, err, map[string]any{"path": abs})
+	}
 	if err != nil {
 		return "", err
 	}
 	if !info.IsDir() {
-		return "", fmt.Errorf("%s is not a directory", abs)
+		return "", refusal(http.StatusBadRequest, codeWorkspaceMissing, fmt.Errorf("%s is not a directory", abs), map[string]any{"path": abs})
 	}
 	return abs, nil
 }