build system: add accidentally ignored compilation_database.rb

.gitignore

@@ -50,7 +50,6 @@
 /po/*.mo
 /po/mkvtoolnix.pot
 /po/qt/*.qm
-/rake.d/compilation_database.rb
 /rake.d/dependency.d
 /share/icons/*/*.h
 /src/*/qt_resources.cpp

rake.d/compilation_database.rb

@@ -0,0 +1,36 @@
+module Mtx
+  module CompilationDatabase
+    @file_name            = "#{$build_dir}/compile_commands.json"
+    @compilation_commands = {}
+
+    def self.database_file_name
+      @file_name
+    end
+
+    def self.read
+      return {} unless FileTest.exists?(@file_name)
+
+      Hash[
+        *JSON.parse(IO.readlines(@file_name).join("")).
+          map { |entry| [ entry["file"], entry ] }.
+          flatten
+      ]
+    end
+
+    def self.write
+      return if @compilation_commands.empty?
+      return if !FileTest.exists?(@file_name) && !c?(:BUILD_COMPILATION_DATABASE)
+
+      entries = self.read.merge(@compilation_commands).values.sort_by { |e| e["file"] }
+      File.open(@file_name, "w") do |f|
+        f.write(JSON.generate(entries, :indent => "  ", :object_nl => "\n", :array_nl => "\n"))
+      end
+    end
+
+    def self.add entry
+      @compilation_commands[entry["file"]] = entry
+    end
+  end
+end
+
+at_exit { Mtx::CompilationDatabase.write }