Implement :enabled-for layer keyword

core/core-configuration-layer.el

@@ -97,7 +97,12 @@ ROOT is returned."
    (disabled :initarg :disabled-for
              :initform nil
              :type list
-             :documentation "A list of layer where this layer is disabled."))
+             :documentation "A list of layers where this layer is disabled.")
+   (enabled :initarg :enabled-for
+            :initform 'unspecified
+            :type (satisfies (lambda (x) (or (listp x) (eq 'unspecified x))))
+            :documentation (concat "A list of layers where this layer is enabled. "
+                                   "(Takes precedence over `:disabled-for'.)")))
   "A configuration layer.")
 
 (defmethod cfgl-layer-owned-packages ((layer cfgl-layer))
@@ -504,6 +509,10 @@ indexed layers for the path."
       (let* ((dir (file-name-as-directory dir))
              (disabled (when (listp layer-specs)
                          (spacemacs/mplist-get layer-specs :disabled-for)))
+             (enabled (if (and (listp layer-specs)
+                               (memq :enabled-for layer-specs))
+                          (spacemacs/mplist-get layer-specs :enabled-for)
+                        'unspecified))
              (variables (when (listp layer-specs)
                           (spacemacs/mplist-get layer-specs :variables)))
              (packages-file (concat dir "packages.el"))
@@ -522,6 +531,7 @@ indexed layers for the path."
         (oset obj :dir dir)
         (when usedp
           (oset obj :disabled-for disabled)
+          (oset obj :enabled-for enabled)
           (oset obj :variables variables))
         (when packages
           (oset obj :packages packages)
@@ -1491,18 +1501,26 @@ wether the declared layer is an used one or not."
          (t
           (configuration-layer//configure-package pkg))))))))
 
+(defun configuration-layer//package-enabled-p (pkg layer)
+  "Returns true if PKG should be configured for LAYER.
+LAYER must not be the owner of PKG."
+  (let* ((owner (configuration-layer/get-layer (car (oref pkg :owners))))
+         (disabled (oref owner :disabled-for))
+         (enabled (oref owner :enabled-for)))
+    (if (not (eq 'unspecified enabled))
+        (memq layer enabled)
+      (not (memq layer disabled)))))
+
 (defun configuration-layer//configure-package (pkg)
   "Configure PKG object."
   (let* ((pkg-name (oref pkg :name))
-         (owner (car (oref pkg :owners)))
-         (owner-layer (configuration-layer/get-layer owner))
-         (disabled-for-layers (oref owner-layer :disabled-for)))
+         (owner (car (oref pkg :owners))))
     (spacemacs-buffer/message (format "Configuring %S..." pkg-name))
     ;; pre-init
     (mapc
      (lambda (layer)
        (when (configuration-layer/layer-usedp layer)
-         (if (memq layer disabled-for-layers)
+         (if (not (configuration-layer//package-enabled-p pkg layer))
              (spacemacs-buffer/message
               (format "  -> ignored pre-init (%S)..." layer))
            (spacemacs-buffer/message
@@ -1524,7 +1542,7 @@ wether the declared layer is an used one or not."
     (mapc
      (lambda (layer)
        (when (configuration-layer/layer-usedp layer)
-         (if (memq layer disabled-for-layers)
+         (if (not (configuration-layer//package-enabled-p pkg layer))
              (spacemacs-buffer/message
               (format "  -> ignored post-init (%S)..." layer))
            (spacemacs-buffer/message

doc/DOCUMENTATION.org

@@ -628,10 +628,33 @@ you can do it with the following layer declaration.
 (defun dotspacemacs/layers ()
   ;; List of configuration layers to load.
   (setq-default dotspacemacs-configuration-layers
-    '(org
+    '(org git
       (auto-completion :disabled-for org git))))
 #+END_SRC
 
+You can also use the =:enabled-for= construct to disable it for /all/ layers
+/except/ those explicitly identified.
+
+#+BEGIN_SRC emacs-lisp
+(defun dotspacemacs/layers ()
+  ;; List of configuration layers to load.
+  (setq-default dotspacemacs-configuration-layers
+    '(java python c-c++
+      (auto-completion :enabled-for java python))))
+#+END_SRC
+
+Note that =:enabled-for= may be an empty list.
+
+#+BEGIN_SRC emacs-lisp
+(defun dotspacemacs/layers ()
+  ;; List of configuration layers to load.
+  (setq-default dotspacemacs-configuration-layers
+    '(java python c-c++
+      (auto-completion :enabled-for))))
+#+END_SRC
+
+=:enabled-for= takes precedence over =:disabled-for= if both are present.
+
 *** Selecting/Ignoring packages of a layer
 By default a declared layer installs/configures all its associated packages. You
 may want to select only some of them or ignoring some of them. This is possible

tests/core/core-configuration-layer-utest.el

@@ -1328,6 +1328,66 @@
      (configuration-layer//configure-package pkg)
      (should (equal '(init) witness)))))
 
+(ert-deftest test-configure-package--enabled-for-unspecified-does-call-pre-post-init ()
+  (let ((pkg (cfgl-package "pkg" :name 'pkg :owners '(layer1)
+                           :pre-layers '(layer2)
+                           :post-layers '(layer3)))
+        configuration-layer--used-layers
+        (configuration-layer--indexed-layers (make-hash-table :size 1024))
+        (witness nil)
+        (mocker-mock-default-record-cls 'mocker-stub-record))
+    (helper--set-layers
+     `(,(cfgl-layer "layer1" :name 'layer1 :enabled-for 'unspecified)
+       ,(cfgl-layer "layer2" :name 'layer2)
+       ,(cfgl-layer "layer2" :name 'layer3)) t)
+    (defun layer1/init-pkg () (push 'init witness))
+    (defun layer2/pre-init-pkg () (push 'pre-init witness))
+    (defun layer3/post-init-pkg () (push 'post-init witness))
+    (mocker-let
+     ((spacemacs-buffer/message (m) ((:output nil))))
+     (configuration-layer//configure-package pkg)
+     (should (equal '(post-init init pre-init) witness)))))
+
+(ert-deftest test-configure-package--enabled-for-nil-does-not-call-pre-post-init ()
+  (let ((pkg (cfgl-package "pkg" :name 'pkg :owners '(layer1)
+                           :pre-layers '(layer2)
+                           :post-layers '(layer3)))
+        configuration-layer--used-layers
+        (configuration-layer--indexed-layers (make-hash-table :size 1024))
+        (witness nil)
+        (mocker-mock-default-record-cls 'mocker-stub-record))
+    (helper--set-layers
+     `(,(cfgl-layer "layer1" :name 'layer1 :enabled-for nil)
+       ,(cfgl-layer "layer2" :name 'layer2)
+       ,(cfgl-layer "layer2" :name 'layer3)) t)
+    (defun layer1/init-pkg () (push 'init witness))
+    (defun layer2/pre-init-pkg () (push 'pre-init witness))
+    (defun layer3/post-init-pkg () (push 'post-init witness))
+    (mocker-let
+        ((spacemacs-buffer/message (m) ((:output nil))))
+      (configuration-layer//configure-package pkg)
+      (should (equal '(init) witness)))))
+
+(ert-deftest test-configure-package--enabled-for-partial ()
+  (let ((pkg (cfgl-package "pkg" :name 'pkg :owners '(layer1)
+                           :pre-layers '(layer2)
+                           :post-layers '(layer3)))
+        configuration-layer--used-layers
+        (configuration-layer--indexed-layers (make-hash-table :size 1024))
+        (witness nil)
+        (mocker-mock-default-record-cls 'mocker-stub-record))
+    (helper--set-layers
+     `(,(cfgl-layer "layer1" :name 'layer1 :enabled-for '(layer2))
+       ,(cfgl-layer "layer2" :name 'layer2)
+       ,(cfgl-layer "layer2" :name 'layer3)) t)
+    (defun layer1/init-pkg () (push 'init witness))
+    (defun layer2/pre-init-pkg () (push 'pre-init witness))
+    (defun layer3/post-init-pkg () (push 'post-init witness))
+    (mocker-let
+        ((spacemacs-buffer/message (m) ((:output nil))))
+      (configuration-layer//configure-package pkg)
+      (should (equal '(init pre-init) witness)))))
+
 ;; ---------------------------------------------------------------------------
 ;; configuration-layer//configure-packages-2
 ;; ---------------------------------------------------------------------------