3.5. ADR Dragon Create Noname

  • EN: Dragon on creation display error if it does not have name

  • PL: Smok przy tworzeniu wyświetla błąd jeżeli nie ma imienia

3.5.1. Option 1

>>> print('Dragon must have a name')
Dragon must have a name

Good:

  • Easy to use

  • User friendly

Bad:

  • You should never print in a class

  • Hard to catch programmatically

  • Less verbose than exception

Example:

>>> dragon = Dragon()
Dragon must have a name

Decision:

  • Rejected, hard to catch programmatically

3.5.2. Option 2

>>> logging.error('Dragon must have a name')
ERROR:root:Dragon must have a name

Good:

  • Easy to use

  • User friendly (more or less)

  • Way better than print

Bad:

  • Hard to catch programmatically

  • Less verbose than exception

Example:

>>> dragon = Dragon()
ERROR:root:Dragon must have a name

Decision:

  • Rejected, hard to catch programmatically

3.5.3. Option 3

>>> raise NameError
Traceback (most recent call last):
NameError:

Good:

  • Easy to use

  • Easy to understand

  • Much better than print and logging

  • Easy to catch programmatically

Bad:

  • Without message it is hard to understand what happened

  • Less user friendly

Example:

>>> dragon = Dragon()
Traceback (most recent call last):
NameError:

Decision:

  • Rejected, without message it is hard to understand what happened

3.5.4. Option 4

>>> raise NameError('Dragon must have a name')
Traceback (most recent call last):
NameError: Dragon must have a name

Good:

  • Easy to use

  • Easy to understand

  • Easy to catch programmatically

  • Verbose

Bad:

  • Requires default value for name, and later checking it

Example:

>>> dragon = Dragon()
Traceback (most recent call last):
NameError: Dragon must have a name

Implementation:

>>> class Dragon:
...     name: str
...
...     def __init__(self, name: str = None) -> None:
...         if name is None:
...             raise NameError('Dragon must have a name')
...         self.name = name

Decision:

  • Candidate

3.5.5. Option 5

>>> dragon = Dragon()
Traceback (most recent call last):
TypeError: Dragon.__init__() missing 1 required positional argument: 'name'

Good:

  • Easy to use

  • Easy to understand

  • Much better than print and logging

  • Easy to catch programmatically

  • Verbose

  • Works out of the box (no code required)

  • Less code to maintain

  • Standard Python message that all developers know

Bad:

  • Very technical error message (not user friendly)

Example:

>>> dragon = Dragon()  
Traceback (most recent call last):
TypeError: ...

Implementation:

>>> class Dragon:
...     name: str
...
...     def __init__(self, name: str, /) -> None: ...

Decision:

  • Candidate

3.5.6. Decision

>>> dragon = Dragon()
Traceback (most recent call last):
TypeError: Dragon.__init__() missing 1 required positional argument: 'name'

Rationale:

  • Easy to use and understand

  • Easy to catch programmatically

  • Works out of the box (no code required)

  • Standard Python message that all developers know

  • Less code to maintain

Implementation:

>>> class Dragon:
...     def __init__(self, name: str, /) -> None: ...