On 19/02/2015 23:57, MRAB wrote:
On 2015-02-19 22:50, Serhiy Storchaka wrote:> Different patterns for
TypeError messages are used in the stdlib:
>
> expected X, Y found
> expected X, found Y
> expected X, but Y found
> expected X instance, Y found
> X expected, not Y
> expect X, not Y
> need X, Y found
> X is required, not Y
> Z must be X, not Y
> Z should be X, not Y
>
> and more.
>
> What the pattern is most preferable?
>
Stylistically, if the first part is in the active voice, then the
second part should also be in the active voice:
expected X, but found Y
The active voice tends to be simpler and easier to parse than the
passive voice.
I think that the word "but" adds clarity here.
Strictly speaking, that message is OK only if it's expecting X itself;
if, in fact, it's expecting an instance of X, then you should really be
saying something along the lines of:
expected X instance, but found Y instance
or:
expected instance of X, but found instance of Y
To me that is a purist argument, but in practice
expected int, but found tuple
is perfectly clear (I have received such messages myself!), and extra
verbiage is just clutter.
Identifying Z may be helpful however, so my feeling would be to stick to
2 patterns - the one above and
Z should be int, not tuple
(You may prefer e.g. "got" to "found", or "must" to "should". But
ideally the usage should be the same throughout.)
Rob Cliffe
> Some messages use the article before X or Y. Should the article be
> used or omitted?
>
Messages tend not to be complete sentences anyway, so I think that it
would be fitting to omit articles.
> Some messages (only in C) truncate actual type name (%.50s, %.80s,
> %.200s, %.500s). Should type name be truncated at all and for how
> limit? Type names newer truncated in TypeError messages raised in
> Python code.
>
Truncating type names is probably not a good idea.
> Some messages enclose actual type name with single quotes ('%s',
> '%.200s'). Should type name be quoted? It is uncommon if type name
> contains spaces.
>
I think that it should be quoted only if it's expecting those
characters, e.g. if it's expecting a closing parenthesis, then it
should say ')'. If, on the other hand, it's expecting a certain type,
then it should give that type unquoted.
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