create/src/Mod/Fem/coding_conventions.md

FEM coding_conventions

These coding rules apply to FEM module code only. Other modules or the base system may use different coding rules especially in naming policy of Python.

Spelling

• Be mindful of spelling. Spell checks are quite often neglected.

• Utilize codespell to discover and quickly correct spelling errors.

  # Find typos
  codespell -q 2 -S *.ts -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez src/Mod/Fem/
  # Interactively fix said typos
  codespell -i 3 -w -S *.ts -L childs,dof,dum,methode,nd,normaly,uint,vertexes,freez src/Mod/Fem/
  

  Notes:

  1. We recommend running the dev version as it uses the most up to date typo dictionaries.
  2. To find the most amount of typos we recommend running a quick pip install --upgrade
     See the codespell docs for more info.

Python and C++

Code formatting

• All files should have a license header
• Unix line endings will be used:
  • a .gitattributes file has been added to ensure line endings of text files are LF
  • use ?w=1 in link address to suppress line ending changes on github
• never use mixed line endings on one file
• 4 Spaces for indent (in this file too ;-))
• no trailing white spaces

Python

Code formatting

• except W503 all Python code is pep8 compliant
• maximal line length is 100
• double quotes as string identifier

Imports

• Python imports should be grouped into three groups:
  • Standard library imports
  • One empty line
  • Third-party imports
  • One empty line
  • FreeCAD-specific imports from module FreeCAD
  • One empty line
  • Other FreeCAD non Gui imports
  • One empty line
  • FreeCAD Gui imports:
    • The import of Gui modules should be guarded by a 'if FreeCAD.GuiUp:'
    • On Gui only modules the guard is not needed
    • Same as above but without an empty line
    • Standard library imports
    • Third-party Gui imports
    • FreeCAD-specific imports from module FreeCADGui
    • other FreeCAD Gui imports
• Each group should be sorted alphabetically
• First the import imports, than the from imports
• On from imports firs the one dot, than two dot and so on imports
• Only one import per line
• Even for from mymodule import mymethod should only be one method
• The above paragraphs highly reduces merge conflicts
• Star import should not be used at all (from mymodule import *)

Naming policy

• snake_case_names
• ClassNames, variable_names_without_capitals and CONSTANTS_USE_CAPITALS, functions_without_capitals
• Function expected to return a value should indicate what is expected, so is_mesh_valid is a good name, but check_mesh is not a good name
• Class names, method names and variable that are locally and not supposed to be used for scripting should start with underscore like _MyInternalClass

Python code formatting tools

• flake8 in source code directory on Linux shell

find src/Mod/Fem/ -name "*\.py" | grep -v InitGui.py | xargs -I [] flake8 --ignore=E266,W503 --max-line-length=100 []

• LGTM
• TODO: check pylint
• Automatic code formatter will not be used for existent code
• For new code if someone would like to use a code formatter black should be used

Coding

• print() vs. FreeCAD.Console.PrintMessage()
  • FreeCAD.Console.PrintMessage() or Log or Error should be used
  • print() should be used for debugging only
  • forum topic
  • BTW: Console prints need a new line where as print does not need one
• type checking:
  • do not use hasattr(obj, "Proxy") and obj.Proxy.Type
  • use method is_of_typ(obj, "TypeString") from module femtool.femutils
• ActiveDocument
  • try to avoid the use of App.ActiveDocument or FreeCAD.ActiveDocument
  • instead try to use some_obj.Document instead
  • try to avoid the use of Gui.ActiveDocument or FreeCADGui.ActiveDocument
  • instead try to use some_obj.ViewObject.Document or some_view_obj.Document
  • activeDocument() is more robust than ActiveDocument
  • forum topic
  • FreeCAD Python console
    • in code examples which will be copied in FreeCAD Python console
    • it is common to use App.ActiveDocument.some_obj or method

Documenting

Python style is preferred over Doxygen style - see ccx tools module in fem tools package - see forum topic

C++

Naming policy

• CamelCase names

Code formatting

• slashes
  • Do not use to many slashes in a row. This could cause trouble with Doxygen.
  • see PR with comment

Icons

Naming plicy

• Command icons use the command name.
• see forum topic