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Type refinements #162

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Type refinements #162

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50e9164
Add parent type argument to NullaryType
Avaq Jun 26, 2017
e983ea2
Reorder types based on new ordering scheme
Avaq Jun 27, 2017
c5f1130
Add refinement support to UnaryType constructor
Avaq Jun 27, 2017
90b7aa3
Add refinement support to BinaryType constructor
Avaq Jun 29, 2017
fa55a10
Remove no longer necessary null-check
Avaq Jun 29, 2017
75a55dd
Incorporate PR feedback
Avaq Jun 29, 2017
aada3db
Add refinement support to RecordType constructor
Avaq Jun 30, 2017
96d562c
Document how to use record type refinement
Avaq Jun 30, 2017
7b0ac2c
Incorporate PR feedback
Avaq Jun 30, 2017
6d6960b
:warning: Change env from Array Any to Array Type
Avaq Jun 30, 2017
02ea18c
Rephrase the documentation using "one" over "we"
Avaq Jun 30, 2017
017a376
Add assertions for record extension
Avaq Jun 30, 2017
1ae62f4
Aleviate minor complaints about documentation
Avaq Jul 5, 2017
4b90668
In-line Options record definition with create definition
Avaq Jul 5, 2017
9708db1
Add Strict type constructor
Avaq Jul 5, 2017
cc92cd2
Rephrase documentation on additional record fields
Avaq Jul 5, 2017
2fce7d9
Incorporate PR feedback
Avaq Jul 5, 2017
f1da1c4
Take all enumerable properties into account for strict record types
Avaq Jul 5, 2017
e08290c
Let record and strict types acknowledge all enumerable properties
Avaq Jul 10, 2017
7b57bc0
WIP: Level Strict and NonEmpty in terms of approach
Avaq Jul 10, 2017
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27 changes: 12 additions & 15 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -797,17 +797,16 @@
//. the type comprising every [`String`][] value except `''`.
//.
//. The given type must satisfy the [Monoid][] and [Setoid][] specifications.
var NonEmpty = UnaryType(
'sanctuary-def/NonEmpty',
functionUrl('NonEmpty'),
Any,
function(x) {
function NonEmpty(parent) {
function test(x) {
return Z.Monoid.test(x) &&
Z.Setoid.test(x) &&
!Z.equals(x, Z.empty(x.constructor));
},
function(monoid) { return [monoid]; }
);
}
function extract(monoid) { return [monoid]; }
var t = UnaryTypeWithUrl('sanctuary-def/NonEmpty', parent, test, extract);
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Using parent as an actual parent type, like I'm doing here, seems like a good idea. Now NonEmpty String will (correctly) be a "refinement" of String.

However, as indicated by the failing unit test, it causes a value of [1] for $NonEmpty($Array($String)), for example, to generate this error message:

NonEmpty (Array String)
         ^^^^^^^^^^^^^^
               1

1) 1 :: Number

The value at position 1 is not a member of ‘Array String’.

Where we would want:

NonEmpty (Array String)
                ^^^^^^
                  1

1) 1 :: Number

The value at position 1 is not a member of ‘String’.

I'm not sure why this happens. Replacing parent with Any solves the issue.

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The problem is that

$.NonEmpty($.Array($.String)).validate([1, 2, 3]).value.propPath

evaluates to ['$1'] rather than ['$1', '$1'] because we first validate the parent type and, if validation fails, make no adjustment to propPath to account for the extra level of nesting introduced by $.NonEmpty.

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That seems like an issue that will bite us in some other way, one day. I don't yet see a solution.

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@Avaq Avaq Jul 10, 2017 •
edited
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In it's general form, I think the issue could be described as: When the validation of a refined type fails on its parent type, the reported propPath may not correctly correspond to the location of the value as it exists in the refined type

We even encounter this issue if we refine a record type to be "strict", as has always been the suggestion:

const User = $.RecordType({ name: $.String, password: $.String });
const StrictUser = $.NullaryType('', '', User, x => Object.keys(x).length ===
                                                    User.keys.length);

const validation = StrictUser.validate({ name: 'bob', password: 1 });
// propPath = [ 'password' ]

StrictUser.types[validation.value.propPath[0]] // => undefined
// the above expression should never return undefined, as the propPath must
// correspond to the types mapping. It does because our propPath is actually
// corresponding to another types mapping!

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@Avaq Avaq Jul 10, 2017 •
edited
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The same problem, biting us somewhere else:

const Point = $.RecordType($.Any, { x: $.Number, y: $.Number });
const Point3D = $.RecordType(Point, { z: $.Number });

const validation = Point3D.validate({ x: 1, y: 'two', z: 3 });
// propPath = [ 'y' ]

Point3D.types[validation.value.propPath[0]] // => undefined

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This is particularly problematic, because the property names described by propPath might exist in both the parent type and the refinement, and validate does not tell us which it was.

return t(parent);
}

//# Nullable :: Type -> Type
//.
Expand Down Expand Up @@ -839,13 +838,11 @@
//. Constructor for strict record types.
//. `$.Strict($.Record($.Any, {name: $.String}))`, for example, is the type
//. comprising every object with exactly one field, `name`, of type `String`.
function Strict(t) {
return NullaryType('sanctuary-def/Strict',
functionUrl('Strict'),
t,
function test(x) {
return t.keys.length === keys(x).length;
});
function Strict(parent) {
function test(x) { return parent.keys.length === keys(x).length; }
function extract(record) { return [record]; }
var t = UnaryTypeWithUrl('sanctuary-def/Strict', parent, test, extract);
return t(parent);
}

//# StrMap :: Type -> Type
Expand Down