Port many layers to new auto-completion

Adds support for ruby, auctex, css, ledger and gtags with new
auto-completion infrastructure. Ticks off many things in #1045

contrib/auctex/packages.el

@@ -10,9 +10,6 @@
     :defer t
     :config
     (progn
-      (when (configuration-layer/layer-usedp 'auto-completion)
-        (company-auctex-init))
-
       (defun auctex/build-view ()
         (interactive)
         (if (buffer-modified-p)
@@ -60,9 +57,16 @@
       (setq-default TeX-parse-self t)
       (setq-default TeX-PDF-mode t))))
 
-(defun auctex/init-company-auctex ()
-  (use-package company-auctex :defer t
-    :if (configuration-layer/layer-usedp 'auto-completion)))
 
 (defun auctex/post-init-evil-matchit ()
   (add-hook 'web-mode-hook 'evil-matchit-mode))
+
+(when (configuration-layer/layer-usedp 'auto-completion)
+  (spacemacs|init-layer-company auctex LaTeX-mode)
+  (defun auctex/init-company-auctex ()
+    (use-package company-auctex :defer t
+      :init (progn
+              (add-to-list 'company-backends-LaTeX-mode 'company-auctex-labels)
+              (add-to-list 'company-backends-LaTeX-mode 'company-auctex-bibs)
+              (add-to-list 'company-backends-LaTeX-mode
+                           '(company-auctex-macros company-auctex-symbols company-auctex-environments))))))

contrib/finance/packages.el

@@ -29,6 +29,7 @@ which require an initialization must be listed explicitly in the list.")
     :defer t
     :init
     (progn
+      (push '(company-capf :with company-yasnippet) company-backends-ledger-mode)
       (setq ledger-post-amount-alignment-column 62)
       (evil-leader/set-key-for-mode 'ledger-mode
         "mhd"   'ledger-delete-current-transaction
@@ -44,3 +45,6 @@ which require an initialization must be listed explicitly in the list.")
         "mt"    'ledger-insert-effective-date
         "my"    'ledger-set-year
         "m RET" 'ledger-set-month))))
+
+(when (configuration-layer/layer-usedp 'auto-completion)
+  (spacemacs|init-layer-company finance ledger-mode))

contrib/lang/html/packages.el

@@ -163,3 +163,7 @@ which require an initialization must be listed explicitly in the list.")
 (defun html/init-slim-mode ()
   (use-package slim-mode
     :defer t))
+
+(when (configuration-layer/layer-usedp 'auto-completion)
+  (spacemacs|init-layer-company html css-mode)
+  (push '(company-css :with company-yasnippet) company-backends-css-mode))

contrib/lang/ruby/packages.el

@@ -128,7 +128,11 @@
   "Initialize Robe mode"
   (use-package robe
     :defer t
-    :init (add-hook 'enh-ruby-mode-hook 'robe-mode)
+    :init
+    (progn
+      (add-hook 'enh-ruby-mode-hook 'robe-mode)
+      (when (configuration-layer/layer-usedp 'auto-completion)
+        (push '(company-robe :with company-yasnippet) company-backends-enh-ruby-mode)))
     :config
     (progn
       (spacemacs|hide-lighter robe-mode)
@@ -173,3 +177,6 @@
       (evil-leader/set-key
         "mtb" 'ruby-test-run
         "mtt" 'ruby-test-run-at-point))))
+
+(when (configuration-layer/layer-usedp 'auto-completion)
+  (spacemacs|init-layer-company ruby enh-ruby-mode))

spacemacs/funcs.el

@@ -834,6 +834,6 @@ If ASCII si not provided then UNICODE is used instead."
   "Initialize a MODE specific company backend variable.
 The variable name format is company-backends-MODE."
   `(defvar ,(intern (format "company-backends-%S" mode))
-     '((company-dabbrev-code company-keywords)
+     '((company-dabbrev-code company-gtags company-etags company-keywords)
        company-files company-dabbrev)
      ,(format "Company backend list for %S" mode)))