C/C++/ObjC language server ccls 0.20181225 release

https://maskray.me/blog/2018-12-25-ccls-release

聖誕發佈新版https://github.com/MaskRay/ccls/releases/tag/0.20181225

workspace/didChangeWatchedFiles works (tested on VSCode and coc.nvim) and file deletion will remove index symbols
.ccls enhancement #171 added new directives %compile_commands.json %h %hpp %objective-c %objective-cpp
-v=1 dumps command line options of files for parsing
fuzzy_match: when the completion filter begins with a letter, builtin macros prefixed with an underscore will not be returned
Support textDocument/declaration and LocationLink[] return types.
Properly handle "exit" #159
Support signatureHelp.signatureInformationparameterInformation.labelOffsetSupport cf. https://github.com/Microsoft/language-server-protocol/issues/640
codeAction: fixed an incompatibility issue with VSCode

Completion

More precise diagnostics/completion: an included file that has been changed does not need to be saved to take effect.
Decreased Content-Length: from 32K to 25K for some cases
On clang < 8, fixed #include < completion for -I dir
Macros are categorized as Text, instead of Interface
Refactor and rename (clang_complete.cc -> sema_manager.cc)
C++17 deduction guide #173

Others

Support multiple -init=: "initializationOptions" from client are applied first, then -init=. Scalar options will be overridden while arrays will get concatenated

重點是

更加精確的 diagnostics/completion(針對#include 中的依賴 unsaved buffers)，之前 cquery/ccls 的做法都不好
檔案刪除、重命名：之前這兩個專案都不會清理掉刪除的檔案 #170
#159 是之前 LSP exit 觸發exit(0)(中斷一個正在寫 cache 的 indexer thread 下次可能讀不出來，但非常罕見)
補全的其他大大小小改進
如果一個 textDocument 的索引未被加載，request (textDocument/documentHighlight textDocument/hover等)會報告not indexed，顯示在 echo area，比較惱人。我在pipeline.cc引入了一個 backlog 解決這一問題，詳見https://github.com/MaskRay/ccls/pull/176。code lens 可以用(add-hook 'lsp-after-open-hook #'ccls-code-lens-mode)而不需要(run-at-time 0.5 nil #'ccls-code-lens-mode)了
增強.ccls和compile_commands.json的協作，詳見 Paul Smith 的分析https://github.com/MaskRay/ccls/issues/115#issuecomment-449455357

其他

ccls/wiki/Emacs 拆分成wiki/lsp-mode和wiki/egot，後者還比較簡陋(歡迎貢獻)
eglot 支援workspace/didChangeWatchedFiles，lsp-mode 尚未
我給 lsp-mode 加了LocationLink支援，targetSelectRange可以指向名字，而targetRange指向輪廓。mouse hover 時可以有可視效果(對於 Emacs 用途不大)
xref.el 的xref-file-location並非表示interface Range的良好選擇，因爲僅能表示點(line column)，不能表示區間。lsp-ui-peek 裏需要區間信息 highlight 文本，無法良好地用 xref 表達，在 lsp-ui-peek 裏的實現有點噁心(希望有人能改好)

;; xref.el
(defclass xref-file-location (xref-location)
  ((file :type string :initarg :file)
   (line :type fixnum :initarg :line :reader xref-location-line)
   (column :type fixnum :initarg :column :reader xref-file-location-column))
  :documentation "A file location is a file/line/column triple.
Line numbers start from 1 and columns from 0.")

;; lsp-ui-peek.el
          (-if-let (uri (gethash "uri" x))
              (-let (((&hash "start" (&hash "line" "character")) (gethash "range" x)))
                (lsp-ui-peek--goto-xref `(:file ,(lsp--uri-to-path uri) :line ,line :column ,character)))
            (-let (((&hash "start" (&hash "line" "character")) (or (gethash "targetSelectionRange" x) (gethash "targetRange" x))))
              (lsp-ui-peek--goto-xref `(:file ,(lsp--uri-to-path (gethash "targetUri" x)) :line ,line :column ,character))))

非常希望看到有人能把 lsp-mode 的 hash tables+string keys ((gethash "range" xx))都改成 plists + keyword keys ((plist-get xx :range))，這樣會讓我感覺還是有希望的……
code lens 我另外也在等待 eglot 的處理：https://github.com/joaotavora/eglot/pull/71，lsp-mode 中的 issue 是https://github.com/emacs-lsp/lsp-mode/issues/361