[nongnu] elpa/dart-mode d333a73 102/192: Add an analyzer-based auto-complete

[ELPA Syncer]

branch: elpa/dart-mode
commit d333a73b3cae664821e2e70a918e134efac589be
Author: Natalie Weizenbaum <nex342@gmail.com>
Commit: Natalie Weizenbaum <nex342@gmail.com>

    Add an analyzer-based auto-complete
---
 CHANGELOG.md |   3 ++
 README.md    |  11 +++++++
 dart-mode.el | 105 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 119 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index bec44d2..3c5845e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,5 +18,8 @@
 * Added a `dart-find-member-refs` command bound to `C-c C-r` which shows a list
   of references to members with a given name.
 
+* Added a `dart-expand` command bound to `M-/` which cycles through possible
+  completions for the text typed by the user.
+
 * `dart-executable-path`'s default value is now set correctly even if the
   executable named `dart` on the user's path is a symlink or a wrapper script.
diff --git a/README.md b/README.md
index 3fc7104..3196096 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,7 @@
   * [Seeing Information](#seeing-information)
   * [Navigation](#navigation)
   * [Search](#search)
+  * [Expansion](#expansion)
 
 ## Installation
 
@@ -79,3 +80,13 @@ the last "Found X results" line, you know for sure you're 
seeing everything!
   press `C-c C-r`. This will show you everywhere a member with that name is
   called, even if it's in a dynamic context and the analyzer can't figure out
   what it's referring to.
+
+### Expansion
+
+If you press `M-/`, the analyzer will try to expand whatever text you've 
already
+typed into a valid identifier. This uses the same logic that IDEs use for
+autocomplete, but the UI works like Emacs' [`dabbrev-expand`][dabbrev] command.
+You can press `M-/` multiple times in a row to cycle through possible
+completions.
+
+[dabbrev]: 
https://www.gnu.org/software/emacs/manual/html_node/emacs/Dynamic-Abbrevs.html
diff --git a/dart-mode.el b/dart-mode.el
index fa528be..130d9e9 100644
--- a/dart-mode.el
+++ b/dart-mode.el
@@ -422,6 +422,7 @@ Any stderr is logged using dart-log. Returns nil if the 
exit code is non-0."
 (define-key dart-mode-map (kbd "C-c C-e") 'dart-find-member-decls)
 (define-key dart-mode-map (kbd "C-c C-r") 'dart-find-member-refs)
 (define-key dart-mode-map (kbd "C-c C-t") 'dart-find-top-level-decls)
+(define-key dart-mode-map (kbd "M-/") 'dart-expand)
 
 ;;; CC indentation support
 
@@ -1350,6 +1351,110 @@ to add a header and otherwise prepare it for displaying 
results."
     (goto-char (+ 1 offset))
     (dart--flash-highlight offset length)))
 
+;;;; Auto-complete
+
+(defvar dart--last-expand-results nil
+  "The results of the last call to `dart-expand'.")
+
+(defvar dart--last-expand-offset nil
+  "The offset of the text inserted by the last call to `dart-expand'.")
+
+(defvar dart--last-expand-length nil
+  "The length of the text inserted by the last call to `dart-expand'.")
+
+(defvar dart--last-expand-index nil
+  "The index into `dart--last-expand-results' for the last call to 
`dart-expand'.")
+
+(defvar dart--last-expand-subscription nil
+  "The last analysis server subscription from a call to `dart-expand'.")
+
+(defun dart-expand ()
+  "Expand previous word using Dart's autocompletion."
+  (interactive "*")
+  (if (and (eq last-command 'dart-expand) dart--last-expand-results)
+      (progn
+        (incf dart--last-expand-index)
+        (when (>= dart--last-expand-index (length dart--last-expand-results))
+          (setq dart--last-expand-index 0))
+        (dart--use-expand-suggestion
+         dart--last-expand-offset
+         dart--last-expand-length
+         (elt dart--last-expand-results dart--last-expand-index)))
+
+    (when dart--last-expand-subscription
+      (dart--analysis-server-unsubscribe dart--last-expand-subscription))
+    (setq dart--last-expand-results nil)
+    (setq dart--last-expand-offset nil)
+    (setq dart--last-expand-length nil)
+    (setq dart--last-expand-index nil)
+    (setq dart--last-expand-subscription nil)
+
+    (-when-let (filename (buffer-file-name))
+      (dart--analysis-server-send
+       "completion.getSuggestions"
+       `(("file" . ,filename)
+         ("offset" . ,(- (point) 1)))
+       (lexical-let ((buffer (current-buffer)))
+         (lambda (response)
+           (-when-let (result (cdr (assoc 'result response)))
+             (lexical-let ((completion-id (cdr (assoc 'id result)))
+                           (first t))
+               (dart--analysis-server-subscribe
+                "completion.results"
+                (setq dart--last-expand-subscription
+                      (lambda (event subscription)
+                        (dart--json-let event
+                            (id results
+                                (offset replacementOffset)
+                                (length replacementLength)
+                                (is-last isLast))
+                          (when is-last (dart--analysis-server-unsubscribe 
subscription))
+
+                          (when (equal id completion-id)
+                            (with-current-buffer buffer
+                              (dart--handle-completion-event results offset 
length first))
+                            (setq first nil))))))))))))))
+
+(defun dart--handle-completion-event (results offset length first)
+  "Handles a completion results event.
+
+If FIRST is non-nil, this is the first completion event for this completion."
+  ;; Get rid of any suggestions that don't match
+  ;; existing characters. The analysis server provides
+  ;; extra suggestions to support search-as-you-type,
+  ;; but we don't do that.
+  (when (> length 0)
+    (lexical-let ((text (buffer-substring (+ offset 1) (+ offset length 1))))
+      (setq results
+            (remove-if-not
+             (lambda (suggestion)
+               (string-prefix-p text (cdr (assoc 'completion suggestion)) t))
+             results))))
+
+  (when (> (length results) 0)
+    ;; Fill the first result so the first call does
+    ;; something. Just save later results for future
+    ;; calls.
+    (when first
+      (setq dart--last-expand-index 0)
+      (setq dart--last-expand-offset (+ offset 1))
+      (dart--use-expand-suggestion (+ offset 1) length (elt results 0)))
+
+    (setq first nil)
+    (setq dart--last-expand-results results)))
+
+(defun dart--use-expand-suggestion (offset length suggestion)
+  "Inserts SUGGESTION at OFFSET and LENGTH."
+  (dart--json-let suggestion
+      (completion
+       (selection-offset selectionOffset))
+    (setq dart--last-expand-length (length completion))
+
+    (goto-char offset)
+    (delete-char length)
+    (save-excursion (insert completion))
+    (forward-char selection-offset)))
+
 
 ;;; Popup Mode