spacemacs/layers/+tools/dash/packages.el

 ;; see conditional package inclusion
(setq dash-packages
      '(
        (dash-at-point :toggle (spacemacs/system-is-mac))
        (helm-dash :requires helm)
        (counsel-dash :requires ivy)
        (zeal-at-point :toggle (or (spacemacs/system-is-linux)
                                   (spacemacs/system-is-mswindows)))))

(defun dash/init-helm-dash ()
  (use-package helm-dash
    :defer t
    :init (spacemacs/set-leader-keys
            "dh" 'helm-dash-at-point
            "dH" 'helm-dash)
    :config (dash//activate-package-docsets helm-dash-docset-newpath)))

(defun dash/init-counsel-dash ()
  (use-package counsel-dash
    :defer t
    :init (spacemacs/set-leader-keys
            "dh" 'counsel-dash-at-point
            "dH" 'counsel-dash)
    :config (dash//activate-package-docsets helm-dash-docset-newpath)))

(defun dash/init-dash-at-point ()
  (use-package dash-at-point
    :defer t
    :init (spacemacs/set-leader-keys
            "dd" 'dash-at-point
            "dD" 'dash-at-point-with-docset)))

(defun dash/init-zeal-at-point ()
  (use-package zeal-at-point
    :defer t
    :init (spacemacs/set-leader-keys
            "dd" 'zeal-at-point
            "dD" 'zeal-at-point-set-docset)
    :config
    ;; This lets users seach in multiple docsets
    (push '(web-mode . "html,css,javascript") zeal-at-point-mode-alist)))