Smalltalk › Pharo › Pharo Smalltalk Developers

About more precise default exception?

_‹ Previous Topic Next Topic _›

Classic

List

Threaded

2 messages Options

stepharong

About more precise default exception?

When I read that, I thought that errorNotIndexable would raise an
Exception different from Error.
But this is not the case and it means that people should write not so good
tests by checking Error
instead of a concrete Exception.

[[[
MyExampleSetTest >> testIllegal
self should: [ empty at: 5 ] raise: Error.
self should: [ empty at: 5 put: #zork ] raise: Error
]]]
We even have a rule that states that we should not catch on Error

at: index
"Primitive. Assumes receiver is indexable. Answer the value of an
indexable element in the receiver. Fail if the argument index is not an
Integer or is out of bounds. Essential. See Object documentation
whatIsAPrimitive. Read the class comment for a discussion about that the
fact
that the index can be a float."

<primitive: 60>
index isInteger ifTrue:
[self class isVariable
ifTrue: [self errorSubscriptBounds: index]
ifFalse: [self errorNotIndexable]].
index isNumber
ifTrue: [^self at: index asInteger]
ifFalse: [self errorNonIntegerIndex]

thoughts comments?

Clément Béra

Re: About more precise default exception?

I agree this exception should be more specific.

By the way one needs to update all the primitive mutating objects, such as at:put:, so that when it fails because it attempts to mutate a read-only object a proper error is raised instead of SubscriptOutOfBounds with an in-bound index.

Maybe an intern can create a specific error for your case, add an error for read-only object and write / update tests for everything.

On Sun, Jan 22, 2017 at 6:28 PM, stepharong <[hidden email]> wrote:

When I read that, I thought that errorNotIndexable would raise an Exception different from Error.
But this is not the case and it means that people should write not so good tests by checking Error
instead of a concrete Exception.

[[[
MyExampleSetTest >> testIllegal
self should: [ empty at: 5 ] raise: Error.
self should: [ empty at: 5 put: #zork ] raise: Error
]]]
We even have a rule that states that we should not catch on Error

at: index
"Primitive. Assumes receiver is indexable. Answer the value of an
indexable element in the receiver. Fail if the argument index is not an
Integer or is out of bounds. Essential. See Object documentation
whatIsAPrimitive. Read the class comment for a discussion about that the fact
that the index can be a float."

<primitive: 60>
index isInteger ifTrue:
[self class isVariable
ifTrue: [self errorSubscriptBounds: index]
ifFalse: [self errorNotIndexable]].
index isNumber
ifTrue: [^self at: index asInteger]
ifFalse: [self errorNonIntegerIndex]

thoughts comments?