Val err details #12

bheylin · 2021-07-05T16:45:05Z

I've added more detail to the ValidationError.

ValidationError::source_type field stores the name of the source type
ValidationError::message stores an error message.
ValidationError::new::<T>(message) fills in the source_type name based on T and stores the message.
I've removed PartialEq (you should always pair PartialEq and Eq) as it was only being used for equality comparisons in the integration tests. Using assert_matches! allows you to avoid equality tests as the pattern matching system does not use equality tests.

- ValidationError should have more detail. - ValidationError::message should maybe have a String so people can use format! to generate the messages.

bheylin · 2021-07-05T16:51:39Z

Looks like my merge went completely wrong.

bheylin · 2021-07-05T17:03:11Z

I reverted the mis-merge of the master branch.

bheylin · 2021-07-05T17:06:31Z

Maybe this closes #5 ?

teenjuna · 2021-07-06T02:34:33Z

It looks like you're deleting .github/workflows/rust.yml

teenjuna · 2021-07-06T02:36:41Z

Why not use assert!(matches!(...)) instead of assert_matches!(...)? I kind of like the first variant more. And it needs no dependency.

prae_macro/src/lib.rs

teenjuna · 2021-07-06T02:47:05Z

I wonder if the fields of the ValidationError should be public. Perhaps we should make it private and use only for the message?

teenjuna · 2021-07-06T02:50:10Z

I also think we should add value: Option<T> field. It could be used by Guarded<_>::new to return provided value in case of fail. Reference:
https://github.com/PabloMansanet/tightness/blob/master/src/core.rs#L95

teenjuna · 2021-07-06T02:57:11Z

Although all of this is starting to be a bit messy. Looking from a UX point of view, the error should say something like failed to create Username from " ": provided value is invalid. For this we need 1) the name of the source type 2) provided value. In case of Guarded<_>::new it should also probably return provided value back (as it owns it)....

teenjuna · 2021-07-06T03:03:13Z

Another idea: we can create two separate default errors for construction/mutation:

ConstructionError<T>(T). Possible message: failed to construct Username(" "): provided value is invalid. It should also contain the value, so the user can take the ownership back.
MutationError<T>. Possible message: failed to mutate Username("valid name") to Username(" "): provided value is invalid.

bheylin · 2021-07-06T07:13:58Z

It looks like you're deleting .github/workflows/rust.yml

I'll sort this out later today, I'm just starting my day here 😉

Why not use assert!(matches!(...)) instead of assert_matches!(...)? I kind of like the first variant more. And it needs no dependency.

assert_matches! outputs a clearer assertion message, assert!(matches!(...)) just outputs that the match fails.

I wonder if the fields of the ValidationError should be public. Perhaps we should make it private and use only for the message?

I was wondering the same. I see this code as a first draft. In the case of this type, making the fields private makes sense as who knows how we want to represent the source_type in future. I also think the we may want to make the message field type String so that it's plays better with format! and constructing messages in general.

I also think we should add value: Option<T> field. It could be used by Guarded<_>::new to return provided value in case of fail. Reference:
https://github.com/PabloMansanet/tightness/blob/master/src/core.rs#L95

I'll take a look at your proposed solutions later on. But one way or the other having access to the input value is critical for a decent error message.

teenjuna · 2021-07-06T08:46:31Z

I'll sort this out later today, I'm just starting my day here 😉

Of course :)

assert_matches! outputs a clearer assertion message, assert!(matches!(...)) just outputs that the match fails.

Fair

I was wondering the same. I see this code as a first draft. In the case of this type, making the fields private makes sense as who knows how we want to represent the source_type in future. I also think the we may want to make the message field type String so that it's plays better with format! and constructing messages in general.

I thought about the String too. We need to think about the use-cases

remove the period.

- String allows for error messages constructed using format! and such macros.

bheylin · 2021-07-07T14:01:39Z

Another idea: we can create two separate default errors for construction/mutation:

1. `ConstructionError<T>(T)`. Possible message: `failed to construct Username("  "): provided value is invalid`. It should also contain the value, so the user can take the ownership back.

2. `MutationError<T>`. Possible message: `failed to mutate Username("valid name") to Username("  "): provided value is invalid`.

I like the idea of separate errors for the separate actions. I'll take a look at adding the value now.

- The message field is removed as there is no need for custom error messages yet. - The type alias is passed given to the Error so it can print it.

teenjuna · 2021-07-07T16:09:46Z

README.md

@@ -47,12 +47,12 @@ let mut u = Username::new(" valid name \n\n").unwrap();
 assert_eq!(u.get(), "valid name"); // now we're talking!

 // This also works for mutations:
-assert!(matches!(u.try_mutate(|u| *u = "   ".to_owned()), Err(prae::ValidationError)));
+assert!(matches!(u.try_mutate(|u| *u = "   ".to_owned()), Err(prae::ConstructionError<String>)));


Shouldn't it be MutationError<String>?

Yea I didn't add the mutation error yet

I want to argue that the generic bound E should be removed. See the comment below.

bheylin · 2021-07-07T16:10:27Z

With the current arch of the validate fn and the ConstructionError the usage is quite clunky if you don't want to make a custom error.

prae::define! {
        pub Username: String
        validate |u| -> Option<prae::ConstructionError::<String>> {
            if u.is_empty() {
                Some(prae::ConstructionError::new("Username", u.clone()))
            } else {
                None
            }
        }
    }

I think that the validate closure should return a Result<(), Err> as that is idiomatic and means that the ? operator can be used in the closure.

use prae;

#[derive(Debug)]
pub struct UsernameError;

prae::define! {
    pub Username: String
    validate |u| -> Result<(), UsernameError> {
        if u.is_empty() {
            Err(UsernameError{})
        } else {
            Ok(())
        }
    }
}

I think prae::Guarded::new should always return a ConstructionError.
The signature should change to pub fn new<V: Into<T>>(v: V) -> Result<Self, ConstructionError> {.
When the user wants to use a custom error it's simply made the std::error::Error::source of ConstructionError.

I would like to capture errors returned from the validate closure of type String and concat that onto the existing ConstructionError message.

lazy_static! {
    static ref SOME_REGEX: Regex = Regex::new(r"^[a-zA-Z0-9 \-]{1,100}$").unwrap();
}

prae::define! {
    pub Username: String
    validate |u| -> Result<(), String> {
        if SOME_REGEX.is_match(s) {
            Ok(())
        } else {
            Err(format!("match failed for regex {}", regex))
        }
    }
}

That would generate an error:

failed to create Username from \"\": provided value is invalid
match failed for regex ^[a-zA-Z0-9 \-]{1,100}$

teenjuna · 2021-07-07T16:11:48Z

prae/tests/ensure.rs

-        un.try_mutate(|u| *u = "".to_owned()).unwrap_err(),
-        prae::ValidationError
-    );
+    let _error: prae::ConstructionError<String> = un.try_mutate(|u| *u = "".to_owned()).unwrap_err();


Why not assert_matches!?

I'll put assert_matches back in. I was having trouble getting the match to compile using the generic param, but all I need is a turbo fish.

The assert_matches! are restored.

teenjuna · 2021-07-07T16:12:52Z

prae/src/core.rs

+    T: fmt::Debug
+{
+    /// The name of the type where this ConstructionError originated.
+    guarded_type_name: String,


Not sure it should be String since we know the type during compile time

I want to print the alias, how would I store that?

The type is quite a mouthful 😄

but.. it could be a &'static str...

Nice catch, the change is pushed.

Yeah, I meant the &'static str, sorry for not being clear

teenjuna · 2021-07-07T16:23:30Z

I think that the validate closure should return a Result<(), Err> as that is idiomatic and means that the ? operator can be used in the closure.

Good point. I agree.

I think prae::Guarded::new should always return a ConstructionError.
The signature should change to pub fn new<V: Into<T>>(v: V) -> Result<Self, ConstructionError> {.
When the user wants to use a custom error it's simply made the std::error::Error::source of ConstructionError.

I don't think it should. The reason why it's generic is because it's meant to be as flexible as possible and return any error. The ConstructionError and MutationError are just convenient default errors. Anyway, it's late in my area, so I'm gonna read your proposal again in the morning.

Also, I have an idea about possible design that will allow user to return custom messages, but I didn't finish it so I also do it a bit later (haven't much time today :)). Anyway, thank you for your help, we'll finish it soon :)

bheylin · 2021-07-07T16:27:16Z

I don't think it should. The reason why it's generic is because it's meant to be as flexible as possible and return any error. The ConstructionError and MutationError are just convenient default errors. Anyway, it's late in my area, so I'm gonna read your proposal again in the morning.

All good, get some rest 😉 We'll talk about it soon.

teenjuna · 2021-07-08T08:42:48Z

So, I looked at it and it seems to me that bringing ConstructionError and MutationError is just impossible with the current code. I don't want to break the usage of the validate with Error::source as its usage will be inconvenient.

Possible solution will be to split the Guarded into EnsureGuarded and ValidateGuarded (as it was in the beginning, if you look at commits history), where EnsureGuarded will explicitly return ConstructionError and MutationError, but it will complicate both the API and the implementation of the macro.

I think right now we can just revert to the HEAD and add information about the type to the ValidatationError, like so:

pub struct ValidationError<T> {
    _ty: PhantomData<T>,
}

impl<T> fmt::Debug for ValidationError<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(
            f,
            "failed to construct/mutate {}: provided value is not valid",
            std::any::type_name::<T>()
        )
    }
}

impl<T> fmt::Display for ValidationError<T> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        <Self as fmt::Debug>::fmt(self, f)
    }
}

impl<T> std::error::Error for ValidationError<T> {}

And change the tests to use assert_matches instead of directly comparing it.

I propose to focus on another topics right now and return to this later. The fact that a user will see the message failed to construct/mutate Username: provided value is not valid is nice for now.

What do you think?

teenjuna · 2021-07-08T11:07:34Z

Although we could probably define ConstructionError<E> and MutationError<E> that are generic over some error E, which can be custom error defined in validate, or just a &'static str for the default error with ensure. In case of custom error, these errors can implement Into<E>, which should allow to use ? to cast them with the Result<..., E> (not sure, didn't test it). Then we can use them in all cases

- There was a plan to have two errors, one for Construction and another for Mutation. This is not going ahead due to it requiring major arch changes.

bheylin · 2021-07-09T10:08:27Z

So, I looked at it and it seems to me that bringing ConstructionError and MutationError is just impossible with the current code. I don't want to break the usage of the validate with Error::source as its usage will be inconvenient.

Agreed for the increase in complexity doesn't justify the value of having a MutationErrorthat provides the value you're mutating. I would argue that knowing the value you're try to mutate to is all you really care about anyway.

I'm happy with the implementation as it is, a single ValidationError that allows me to see the alias name and the value that failed to validate.

bheylin · 2021-07-09T10:12:25Z

Although we could probably define ConstructionError<E> and MutationError<E> that are generic over some error E, which can be custom error defined in validate, or just a &'static str for the default error with ensure. In case of custom error, these errors can implement Into<E>, which should allow to use ? to cast them with the Result<..., E> (not sure, didn't test it). Then we can use them in all cases

I think this is also needless complexity for the value of having two Errors types. Let's keep it to one Error type until the need arises to make two.

bheylin · 2021-07-09T10:14:09Z

I would like to implement validate returning a Result<(), E> in a separate branch so that this change is just enough to fix #5.

teenjuna · 2021-07-09T11:20:09Z

prae/src/lib.rs

 #[cfg(test)]
 mod test_deps {
+    use assert_matches as _;
    use serde as _;
    use serde_json as _;
 }


Btw, why is this necessary?

I mean the whole test_deps business

I added the lint to warn about unused crate dependencies.

#![warn(unused_crate_dependencies)]

But it give's false positives when buliding the separate integration test binaries.

❯ cargo test Compiling prae_macro v0.2.1 (/home/brianh/Projects/third_party/prae/prae_macro) Compiling prae v0.4.5 (/home/brianh/Projects/third_party/prae/prae) warning: external crate `assert_matches` unused in `prae`: remove the dependency or add `use assert_matches as _;` | note: the lint level is defined here --> prae/src/lib.rs:71:9 | 71 | #![warn(unused_crate_dependencies)] | ^^^^^^^^^^^^^^^^^^^^^^^^^ = help: remove unnecessary dependency `assert_matches` warning: external crate `serde` unused in `prae`: remove the dependency or add `use serde as _;` | = help: remove unnecessary dependency `serde` warning: external crate `serde_json` unused in `prae`: remove the dependency or add `use serde_json as _;` | = help: remove unnecessary dependency `serde_json` warning: 3 warnings emitted Finished test [unoptimized + debuginfo] target(s) in 0.73s Running unittests (target/debug/deps/prae-dc495198ddde61f3)

Oh, now I get it. I'll add a comment referencing the related issue: rust-lang/rust#57274

teenjuna · 2021-07-09T11:23:08Z

prae_macro/src/lib.rs

                let f: fn(&Self::Target) -> bool = #closure;
-                if f(v) { None } else { Some(prae::ValidationError) }
+                if f(v) { None } else { Some(prae::ValidationError::<#ty>::new(stringify!(#ident), v.clone()) ) }


What if the type is not clone? In this case the user will use Guarded::mutate instead of Guarded::try_mutate, but they both use validate

Yeah, exactly. The following code works on HEAD but not on this branch:

#[derive(Debug)] struct User { name: String, } prae::define! { ValidUser: User ensure |u: &User| !u.name.is_empty() }

It's either clone, copy or have the error manage reference lifetimes. I would like to avoid having lifetimes as that constraint will leak into the users code.

Maybe we can add a nicer message though, instead of a compile error emanating from the proc macro?

I guess it's also can't be done with the current code. Introducing ConstructionError<E> and MutationError<E> should solve the issue, since we'll be able to insert the value: T inside Guarded::new and Guarded::try_mutate

I don't see a way around cloning, as we have to clone at some point so the error can store the value, or.... you convert the value to a string which requires T: Debug or T: DIsplay.

Requiring Clone on a type is a reasonable expectation given that it's trivial to implement and it's the exception that you see types that are not clone-able.

The latest commit removes the value.

Making it T: Debug and turning it into string is a reasonable workaround! But expecting the value to be always Clone is a no go, since the library must be available for as many use cases as possible. Sometimes making your value !Clone is a design choice, and we must tolerate this.

Do you want to add str_value: String or should I do it?

I can do it. I'll update the non_clone test too.

ValidationError::value is reinstated as a String, changes are pushed.

- The value would force the users type to implement `Clone`.

- This allows the error to store a value without a generic `T: Clone + Debug`

… val_err_details

teenjuna · 2021-07-09T13:53:32Z

Perfect!

ObsceneGiraffe added 2 commits July 5, 2021 18:31

Added a source_type and message field to ValidationError.

9c2a110

- ValidationError should have more detail. - ValidationError::message should maybe have a String so people can use format! to generate the messages.

Forgot the changes in lib.

84a0748

teenjuna reviewed Jul 6, 2021

View reviewed changes

prae_macro/src/lib.rs Outdated Show resolved Hide resolved

teenjuna marked this pull request as draft July 6, 2021 09:47

bheylin force-pushed the val_err_details branch from fdda5c4 to 84a0748 Compare July 7, 2021 11:25

ObsceneGiraffe added 4 commits July 7, 2021 15:42

Merge branch 'master' into val_err_details

da75369

Made the ValidationError message for Ensure closures lowercase and

545cf7c

remove the period.

Debug nad Display impls for ValidationError use the message field.

228ef1d

ValidationError::message retyped from &str to String.

bfa720a

- String allows for error messages constructed using format! and such macros.

ConstructionError includes the input value in the error mesasge.

bf23b9c

- The message field is removed as there is no need for custom error messages yet. - The type alias is passed given to the Error so it can print it.

teenjuna reviewed Jul 7, 2021

View reviewed changes

Restored the assert_matches in the tests.

25abe8f

Made the ConstructionError::guarded_type_name a &'static str.

293c758

Renamed ConstructionError back to ValidationError.

db02884

- There was a plan to have two errors, one for Construction and another for Mutation. This is not going ahead due to it requiring major arch changes.

Fixed a sloppy rename.

3adae1f

teenjuna marked this pull request as ready for review July 9, 2021 11:09

teenjuna reviewed Jul 9, 2021

View reviewed changes

teenjuna and others added 8 commits July 9, 2021 18:24

Minor fixes

5db539b

Add comment about test test_deps

6a9684a

Check if define! works with non-clonable types

426e4bc

Removed value from ValidationError.

c85f522

- The value would force the users type to implement `Clone`.

Reinstated value to ValidationError but as a String.

1cc5924

- This allows the error to store a value without a generic `T: Clone + Debug`

Remove junk file

b779b76

Merge branch 'val_err_details' of github.com:ObsceneGiraffe/prae into…

49409f8

… val_err_details

Fix comment

39e8928

teenjuna merged commit 427c71e into teenjuna:master Jul 9, 2021

bheylin deleted the val_err_details branch July 12, 2021 16:24

Val err details #12

Val err details #12

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