PyCharm 2018.3 Help


Flow is a static type checker that brings type annotations to JavaScript. PyCharm recognizes Flow structures and provides syntax highlighting for them on all operating systems.

Installing Flow

  • Open the built-in PyCharm Terminal (Alt+F12) and at the command prompt, type:
    • npm install --global flow-bin to install Flow globally.

    • npm install --save-dev flow-bin to install Flow as a development dependency.

Configuring Flow in PyCharm

To have PyCharm recognize Flow structures, provide correct syntax highlighting, report errors properly, and avoid false-positive error highlighting, change the JavaScript language level to Flow, add a .flowconfig configuration file to your project, and supply every file to be checked with a // @flow comment on top.

To change the language level to Flow

  1. In the Settings/Preferences dialog (Ctrl+Alt+S), click JavaScript under Languages and Frameworks. The JavaScript page opens.

  2. From the JavaScript Language Version drop-down list, choose Flow.

  3. In the Flow package or executable field, specify the path to the node_modules\flow-bin package or the Flow binary executable file. To use node_modules\.bin\flow make sure the path to Node.js is added to the PATH environment variable.

  4. In the Use Flow server for: area, specify the basis for coding assistance by selecting or clearing the following checkboxes:
    • Type checking: When this checkbox is selected, syntax and error highlighting is provided based on the data received from the Flow server. When the checkbox is cleared, only the basic internal PyCharm highlighting is available.

    • Navigation, code completion, and type hinting: When this checkbox is selected, suggestion lists for reference resolution and code completiong contain both suggestions retrieved from integration with Flow and suggestions calculated by PyCharm. When the checkbox is cleared, references are resolved through PyCharm calculation only.

    The checkboxes are available only when the path to the Flow executable file is specified.
  5. Keep the Save all modified files automatically checkbox selected to ensure that Flow is applied continuously because Flow checks the current files only after all the other modified files are saved.

To generate a .flowconfig configuration file in your project

  • Open the embedded Terminal (Alt+F12) and type flow init at the command prompt.

To enable Flow in a file

  • Add a // @flow comment at the top of it: just type flow, press Tab, and PyCharm will expand it into // @flow.

Last modified: 27 February 2019

See Also

Language and Framework-Specific Guidelines: