ArduinoBackend.library_available?() to check whether libraries exist

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `shiftIn()` and `shiftOut()`
 - `CIConfig.is_default` to detect when the default configuration is used
 - `ArduinoBackend.boards_installed?` to detect whether a board family (or package, like `arduino:avr`) is installed
+- `ArduinoBackend.library_available?` to detect whether the library manager knows of a library
 
 ### Changed
 - Rubocop expected syntax downgraded from ruby 2.6 to 2.5

lib/arduino_ci/arduino_backend.rb

@@ -136,6 +136,15 @@ def install_boards(boardfamily)
       result[:success]
     end
 
+    # Find out if a library is available
+    #
+    # @param name [String] the library name
+    # @return [bool] whether the library can be installed via the library manager
+    def library_available?(name)
+      # the --names flag limits the size of the response to just the name field
+      capture_json("lib", "search", "--names", name)[:json]["libraries"].any? { |l| l["name"] == name }
+    end
+
     # @return [Hash] information about installed libraries via the CLI
     def installed_libraries
       capture_json("lib", "list")[:json]

spec/arduino_backend_spec.rb

@@ -56,6 +56,13 @@ def get_sketch(dir, file)
       expect(fake_lib.path).to eq(expected_dir)
       expect(fake_lib.installed?).to be false
     end
+
+    it "knows whether libraries exist in the manager" do
+      expect(backend.library_available?("OneWire")).to be true
+
+      # TODO: replace with a less offensive library name guaranteed never to exist?
+      expect(backend.library_available?("fuck")).to be false
+    end
   end
 
   context "board_manager" do