Code contracts, do you use them?
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In particular, I was just perusing the Code Contracts[^] class in .NET 4 / 4.5, so I thought I'd take a quick survey of the community: 1. Do you routinely verify the expected parameter values that your method receives? 2. Do you verify post-conditions (you're method is returning something correct)? 3. Do you use the Contract class, or are you happy with Debug.Assert... and its variants? 4. Do you use your own variant, something like the Contract class? Just curious. :) Marc
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Computational Types in C# and F##1 and #3 all the time. I use
Debug.Assert()to validate incoming parameters ofinternalandprivatemethods, and throwArgumentExceptionin the case of failingpublicandprotected virtualmethods (i.e. APIs my clients can call). /raviMy new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com
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In particular, I was just perusing the Code Contracts[^] class in .NET 4 / 4.5, so I thought I'd take a quick survey of the community: 1. Do you routinely verify the expected parameter values that your method receives? 2. Do you verify post-conditions (you're method is returning something correct)? 3. Do you use the Contract class, or are you happy with Debug.Assert... and its variants? 4. Do you use your own variant, something like the Contract class? Just curious. :) Marc
Reverse Engineering Legacy Applications
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Computational Types in C# and F##1 & #2 yes - #3 & #4 no because I'd not heard of them. Gets my five for something new to me, and I'll have a look in more detail later.
Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water
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In particular, I was just perusing the Code Contracts[^] class in .NET 4 / 4.5, so I thought I'd take a quick survey of the community: 1. Do you routinely verify the expected parameter values that your method receives? 2. Do you verify post-conditions (you're method is returning something correct)? 3. Do you use the Contract class, or are you happy with Debug.Assert... and its variants? 4. Do you use your own variant, something like the Contract class? Just curious. :) Marc
Reverse Engineering Legacy Applications
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Computational Types in C# and F#1. Yes, for externally visible access points (property setters, public methods and constructors) if it matters – it's surprising how rarely it seems to matter in the real world, though. Most variables are constrained only by the type you choose for them. 2. This is what unit tests are for. I don't put checks inside the code. You're in full control of what you return, so there's no excuse for it being 'incorrect'. 3. I use a unit testing framework and whatever assertions it provides, not in-code assertions. 4. No
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1, 2 and 3 - yes. 4 - used to.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
Pete O'Hanlon wrote:
4 - used to.
Any reason you stopped? And thanks for the reply! Marc
Reverse Engineering Legacy Applications
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Computational Types in C# and F# -
#1 and #3 all the time. I use
Debug.Assert()to validate incoming parameters ofinternalandprivatemethods, and throwArgumentExceptionin the case of failingpublicandprotected virtualmethods (i.e. APIs my clients can call). /raviMy new year resolution: 2048 x 1536 Home | Articles | My .NET bits | Freeware ravib(at)ravib(dot)com
Cool, thanks for the reply! (BTW, I'm impressed that you take the time to highlight your
codepieces!) MarcReverse Engineering Legacy Applications
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Pete O'Hanlon wrote:
4 - used to.
Any reason you stopped? And thanks for the reply! Marc
Reverse Engineering Legacy Applications
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Computational Types in C# and F#Because we started using MS Code Contracts. We talked about them before[^].
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
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lewax00 wrote:
I didn't even know that existed. I'll probably use it now.
:cool: For further reading: Contracts[^] - this has moved out of the "research" dept. and into .NET 4 and 4.5 I liked this article.[^] Marc
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Computational Types in C# and F# -
#1 & #2 yes - #3 & #4 no because I'd not heard of them. Gets my five for something new to me, and I'll have a look in more detail later.
Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water
OriginalGriff wrote:
Gets my five for something new to me, and I'll have a look in more detail later.
:cool: and thanks! Marc
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Computational Types in C# and F# -
1. Yes, for externally visible access points (property setters, public methods and constructors) if it matters – it's surprising how rarely it seems to matter in the real world, though. Most variables are constrained only by the type you choose for them. 2. This is what unit tests are for. I don't put checks inside the code. You're in full control of what you return, so there's no excuse for it being 'incorrect'. 3. I use a unit testing framework and whatever assertions it provides, not in-code assertions. 4. No
BobJanova wrote:
This is what unit tests are for. I don't put checks inside the code. You're in full control of what you return, so there's no excuse for it being 'incorrect'.
Agreed, though there seems to be an interest / suport for post conditions: Postconditions have been harder to express until now, but this attitude is likely to encourage their enforcement in release builds too: a guarantee that the method really will never silently return a value that the contract forbids or leave the object in an invalid state. Source[^] Marc
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Because we started using MS Code Contracts. We talked about them before[^].
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
Pete O'Hanlon wrote:
Because we started using MS Code Contracts. We talked about them before[^].
hahahaha! Just call me Emu (the bird apparently has no memory of the previous day's events.) I certainly didn't remember that. Thank you for the link! Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
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Computational Types in C# and F# -
#1 & #2 yes - #3 & #4 no because I'd not heard of them. Gets my five for something new to me, and I'll have a look in more detail later.
Ideological Purity is no substitute for being able to stick your thumb down a pipe to stop the water
And I thought you hung on my every word: Article 1[^] and Article 2[^]
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
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lewax00 wrote:
I didn't even know that existed. I'll probably use it now.
:cool: For further reading: Contracts[^] - this has moved out of the "research" dept. and into .NET 4 and 4.5 I liked this article.[^] Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
My Blog
Computational Types in C# and F# -
In particular, I was just perusing the Code Contracts[^] class in .NET 4 / 4.5, so I thought I'd take a quick survey of the community: 1. Do you routinely verify the expected parameter values that your method receives? 2. Do you verify post-conditions (you're method is returning something correct)? 3. Do you use the Contract class, or are you happy with Debug.Assert... and its variants? 4. Do you use your own variant, something like the Contract class? Just curious. :) Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
My Blog
Computational Types in C# and F#1. Yes, I routinely check inputs when the inputs matter, which is not always the case. 2. In some cases, usually the higher levels in the architecture will do more post-condition checking, as they tend to be aggregating lower-level results. 3. Don't use Code Contracts. I'm happy with if(condition) throw new... 4. see 3
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And I thought you hung on my every word: Article 1[^] and Article 2[^]
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
Pete O'Hanlon wrote:
And I thought you hung on my every word:
Those two articles are better than anything else I've read on the subject. Marc
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Computational Types in C# and F# -
Thanks, the article looks pretty in depth (only skimmed it for now, but it's bookmarked for later) :thumbsup:
lewax00 wrote:
Thanks, the article looks pretty in depth
And Pete's articles (he links to them here[^] are the best I've encountered on the subject of the
Contractclass. MarcReverse Engineering Legacy Applications
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Computational Types in C# and F# -
Pete O'Hanlon wrote:
And I thought you hung on my every word:
Those two articles are better than anything else I've read on the subject. Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
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Computational Types in C# and F#Gosh shucks. :-O Who am I kidding? I lap up the attention.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
-
In particular, I was just perusing the Code Contracts[^] class in .NET 4 / 4.5, so I thought I'd take a quick survey of the community: 1. Do you routinely verify the expected parameter values that your method receives? 2. Do you verify post-conditions (you're method is returning something correct)? 3. Do you use the Contract class, or are you happy with Debug.Assert... and its variants? 4. Do you use your own variant, something like the Contract class? Just curious. :) Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
My Blog
Computational Types in C# and F#I've tried it, and stopped using it. The problem with Code Contracts is three-fold:
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It's a boil-the-ocean proposition. Everything must use Code Contracts (including 3rd party libs!) or you'll drown in false positives.
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It lacks language support. This code will give false positives, warning you that list might be a null reference:
private readonly List<int> list = new List<int>();
...
void DoSomething()
{
Console.Write(list.Length);
}Another example of the pain of no language support is when it comes to declaring contracts on interfaces. You actually have to create a dummy class that implements the interface, then put contracts on that. YUCK!
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Poor library support. Most libraries, even the .NET framework itself or its subsets, don't do Code Contracts well, or at all. I remember doing some Silverlight code a year or two ago, and many of the methods were missing obvious contracts.
These things combined result in many false positives. To get rid of those false positives, you must write code to reassure the contract checker that everything's gonna be OK. Not fun. Not worth it. Bottom line: contracts could be great. But it needs broad support from libraries and languages, and that doesn't exist today, and probably won't tomorrow.
My Messianic Jewish blog: Kineti L'Tziyon My software blog: Debugger.Break() Judah Himango
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I've tried it, and stopped using it. The problem with Code Contracts is three-fold:
-
It's a boil-the-ocean proposition. Everything must use Code Contracts (including 3rd party libs!) or you'll drown in false positives.
-
It lacks language support. This code will give false positives, warning you that list might be a null reference:
private readonly List<int> list = new List<int>();
...
void DoSomething()
{
Console.Write(list.Length);
}Another example of the pain of no language support is when it comes to declaring contracts on interfaces. You actually have to create a dummy class that implements the interface, then put contracts on that. YUCK!
-
Poor library support. Most libraries, even the .NET framework itself or its subsets, don't do Code Contracts well, or at all. I remember doing some Silverlight code a year or two ago, and many of the methods were missing obvious contracts.
These things combined result in many false positives. To get rid of those false positives, you must write code to reassure the contract checker that everything's gonna be OK. Not fun. Not worth it. Bottom line: contracts could be great. But it needs broad support from libraries and languages, and that doesn't exist today, and probably won't tomorrow.
My Messianic Jewish blog: Kineti L'Tziyon My software blog: Debugger.Break() Judah Himango
Judah Himango wrote:
The problem with Code Contracts is three-fold:
Wow. Thank you for the detailed explanation! That provides some really valuable counterpoint. Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
My Blog
Computational Types in C# and F# -
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Gosh shucks. :-O Who am I kidding? I lap up the attention.
*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
Pete O'Hanlon wrote:
I lap up the attention.
Well, here's[^] your opportunity for more attention. :) Seriously though, I was wondering what your thoughts were on Judah's post - it seems like he brings up some significant issues. Marc
Reverse Engineering Legacy Applications
How To Think Like a Functional Programmer
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Computational Types in C# and F# -
I've tried it, and stopped using it. The problem with Code Contracts is three-fold:
-
It's a boil-the-ocean proposition. Everything must use Code Contracts (including 3rd party libs!) or you'll drown in false positives.
-
It lacks language support. This code will give false positives, warning you that list might be a null reference:
private readonly List<int> list = new List<int>();
...
void DoSomething()
{
Console.Write(list.Length);
}Another example of the pain of no language support is when it comes to declaring contracts on interfaces. You actually have to create a dummy class that implements the interface, then put contracts on that. YUCK!
-
Poor library support. Most libraries, even the .NET framework itself or its subsets, don't do Code Contracts well, or at all. I remember doing some Silverlight code a year or two ago, and many of the methods were missing obvious contracts.
These things combined result in many false positives. To get rid of those false positives, you must write code to reassure the contract checker that everything's gonna be OK. Not fun. Not worth it. Bottom line: contracts could be great. But it needs broad support from libraries and languages, and that doesn't exist today, and probably won't tomorrow.
My Messianic Jewish blog: Kineti L'Tziyon My software blog: Debugger.Break() Judah Himango
Judah Himango wrote:
- It's a boil-the-ocean proposition. Everything must use Code Contracts (including 3rd party libs!) or you'll drown in false positives.
- It lacks language support. This code will give false positives, warning you that list might be a null reference:
This should only happen if you're doing static checking. If you do runtime checking, you only see the contract checks, so the example you quote won't trigger anything. What I would expect to see here is (assuming that we can only call
DoSomethingafter it's had some data added into it).*pre-emptive celebratory nipple tassle jiggle* - Sean Ewington
"Mind bleach! Send me mind bleach!" - Nagy Vilmos
CodeStash - Online Snippet Management | My blog | MoXAML PowerToys | Mole 2010 - debugging made easier
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