Atom + YouCompleteMe

config.cson

"*":
  "atom-beautify":
    general:
      _analyticsUserId: "adfadsfadsfd"
    ruby:
      beautify_on_save: true
  "build-ninja":
    ninjaOptions: [
      "-j10"
    ]
    subdirs: [
      "out/gn"
    ]
  "clang-format":
    formatCOnSave: false
    formatCPlusPlusOnSave: false
  core:
    customFileTypes:
      "source.cpp": [
        "h"
      ]
    disabledPackages: [
      "metrics"
      "exception-reporting"
    ]
    telemetryConsent: "limited"
  editor:
    fontSize: 17
    showIndentGuide: true
    showInvisibles: true
    tabType: "soft"
  "exception-reporting":
    userId: "adfadfadasdf"
  linter: {}
  "linter-eslint":
    eslintrcPath: "/Users/sbc/.eslintrc"
    useGlobalEslint: true
  "linter-ui-default":
    panelHeight: 69
    showPanel: true
  pigments:
    autocompleteSuggestionsFromValue: true
  "tree-view":
    hideIgnoredNames: true
    hideVcsIgnoredFiles: true
  welcome:
    showOnStartup: false
  whitespace:
    ensureSingleTrailingNewline: false
  "you-complete-me":
    globalExtraConfig: "/Users/your-name/.chromium/tools/vim/chromium.ycm_extra_conf.py"
    ycmdPath: "/Users/your-name/.ycmd/"
".java.source":
  editor:
    preferredLineLength: 100
    tabLength: 4

pre-requisite.txt

// install atom-you-complete-me https://atom.io/packages/you-complete-me
// clone ycmd https://github.com/Valloric/ycmd move it to ~/.ycmd run build in ~/.ycmd/ycmd ./build.py --all
// clone chromium from https://github.com/scheib/chromium it conrains 7GB
// goto ~/.atom/config.cson look for the two lines below and modify them
//  globalExtraConfig: "/Users/your-name/.chromium/tools/vim/chromium.ycm_extra_conf.py"
//  ycmdPath: "/Users/your-name/.ycmd/"