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Return parsed type rather than type itself
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Closes #4
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@Avaq
Avaq committed Apr 13, 2017
1 parent c52f2ae commit 2114da6
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Showing 2 changed files with 105 additions and 54 deletions.
92 changes: 58 additions & 34 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -20,39 +20,27 @@
//. purpose: the [`typeof`][1] operator and [`Object.prototype.toString`][2].
//. Each has pros and cons, but neither supports user-defined types.
//.
//. This package specifies an [algorithm][3] for deriving a _type identifier_
//. from any JavaScript value, and exports an implementation of the algorithm.
//. Authors of algebraic data types may follow this specification in order to
//. make their data types compatible with the algorithm.
//. This package exports a function which derives a _type identifier_ from any
//. JavaScript value, and a [specification][3] for customizing the type
//. isdentifier of a value.
//.
//. ### Algorithm
//.
//. 1. Take any JavaScript value `x`.
//.
//. 2. If `x` is `null` or `undefined`, go to step 6.
//.
//. 3. If `x.constructor` evaluates to `null` or `undefined`, go to step 6.
//.
//. 4. If `x.constructor.prototype === x`, go to step 6. This check prevents a
//. prototype object from being considered a member of its associated type.
//.
//. 5. If `typeof x.constructor['@@type']` evaluates to `'string'`, return
//. the value of `x.constructor['@@type']`.
//.
//. 6. Return the [`Object.prototype.toString`][2] representation of `x`
//. without the leading `'[object '` and trailing `']'`.
//.
//. ### Compatibility
//. ### Specification
//.
//. For an algebraic data type to be compatible with the [algorithm][3]:
//.
//. - every member of the type must have a `constructor` property pointing
//. - every member of the type MUST have a `constructor` property pointing
//. to an object known as the _type representative_;
//.
//. - the type representative must have a `@@type` property; and
//. - the type representative MUST have a `@@type` property;
//.
//. - the type representative's `@@type` property (the _type identifier_)
//. must be a string primitive, ideally `'<npm-package-name>/<type-name>'`.
//. MUST be a string primitive; and
//.
//. - the `@@type` property SHOULD have format:
//. `'<namespace>/<name>@<version>'` - where `namespace` SHOULD equal the
//. NPM package name which defines the type, `name` SHOULD be the unique
//. name of the type, and `version` MAY be a numeric value representing
//. the version of the type.
//.
//. For example:
//.
Expand Down Expand Up @@ -88,17 +76,21 @@
//. var Identity = require('my-package').Identity;
//. var type = require('sanctuary-type-identifiers');
//.
//. type(null); // => 'Null'
//. type(true); // => 'Boolean'
//. type([1, 2, 3]); // => 'Array'
//. type(Identity); // => 'Function'
//. type(Identity(0)); // => 'my-package/Identity'
//. type(null); // => {namespace: null, name: 'Null', version: null}
//. type(true); // => {namespace: null, name: 'Boolean', version: null}
//. type([1, 2, 3]); // => {namespace: null, name: 'Array', version: null}
//. type(Identity); // => {namespace: null, name: 'Function', version: null}
//. type(Identity(0)); // => {
//. // namespace: 'my-package',
//. // name: 'Identity',
//. // version: null
//. // }
//. ```
//.
//.
//. [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/typeof
//. [2]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString
//. [3]: #algorithm
//. [3]: #specification

(function(f) {

Expand All @@ -119,14 +111,46 @@
// $$type :: String
var $$type = '@@type';

// type :: Any -> String
// RPARSE :: RegExp
var RPARSE = /^(?:([^/\n\r]+)\/)?(.+?)(?:@(\d+))?$/;

// TypeIdentifier :: (a, b, c) -> TypeIdentifier a b c
function TypeIdentifier(namespace, name, version) {
return {
namespace: namespace,
name: name,
version: version
};
}

// parseTypeIdentifier :: String
// -> TypeIdentifier String? String Number?
function parseTypeIdentifier(s) {
var parsed = RPARSE.exec(s);
// parsed is null if the string was empty, or contained newlines
if (!parsed) return TypeIdentifier(null, s, null);
return TypeIdentifier(
parsed[1] || null,
parsed[2],
parsed[3] ? parseInt(parsed[3], 10) : null
);
}

// parseNativeType :: Any -> TypeIdentifier Null String Null
function parseNativeType(x) {
var parsed = Object.prototype.toString.call(x)
.slice('[object '.length, -']'.length);
return TypeIdentifier(null, parsed, null);
}

// type :: Any -> String
function type(x) {
return x != null &&
x.constructor != null &&
x.constructor.prototype !== x &&
typeof x.constructor[$$type] === 'string' ?
x.constructor[$$type] :
Object.prototype.toString.call(x).slice('[object '.length, -']'.length);
parseTypeIdentifier(x.constructor[$$type]) :
parseNativeType(x);
}

return type;
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67 changes: 47 additions & 20 deletions test/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ function Identity(x) {
Identity['@@type'] = 'my-package/Identity';


var MaybeTypeRep = {'@@type': 'my-package/Maybe'};
var MaybeTypeRep = {'@@type': 'my-package/Maybe@1'};

// Nothing :: Maybe a
var Nothing = {constructor: MaybeTypeRep, isNothing: true, isJust: false};
Expand All @@ -33,25 +33,52 @@ function Just(x) {
return {constructor: MaybeTypeRep, isNothing: false, isJust: true, value: x};
}

function mock($$type) {
return {constructor: {'@@type': $$type}};
}

function parsed(namespace, name, version) {
return {namespace: namespace, name: name, version: version};
}

function named(name) {
return parsed(null, name, null);
}

test('type', function() {
eq(type(null), 'Null');
eq(type(undefined), 'Undefined');
eq(type({constructor: null}), 'Object');
eq(type({constructor: {'@@type': null}}), 'Object');
eq(type({constructor: {'@@type': new String('')}}), 'Object');
eq(type(Identity(42)), 'my-package/Identity');
eq(type(Identity), 'Function');
eq(type(Identity.prototype), 'Object');
eq(type(Nothing), 'my-package/Maybe');
eq(type(Just(0)), 'my-package/Maybe');
eq(type(Nothing.constructor), 'Object');

eq(type(false), 'Boolean');
eq(type(0), 'Number');
eq(type(''), 'String');

eq(type(new Boolean(false)), 'Boolean');
eq(type(new Number(0)), 'Number');
eq(type(new String('')), 'String');
eq(type(null), named('Null'));
eq(type(undefined), named('Undefined'));

eq(type({constructor: null}), named('Object'));
eq(type(mock(null)), named('Object'));
eq(type(mock(new String(''))), named('Object'));
eq(type(mock('Type')), named('Type'));

eq(type(mock('package/Type')), parsed('package', 'Type', null));
eq(type(mock('package/Type/X')), parsed('package', 'Type/X', null));
eq(type(mock('')), parsed(null, '', null));
eq(type(mock('/Type')), parsed(null, '/Type', null));
eq(type(mock('@0')), parsed(null, '@0', null));
eq(type(mock('foo/\n@1')), parsed(null, 'foo/\n@1', null));
eq(type(mock('Type@0')), parsed(null, 'Type', 0));
eq(type(mock('Type@1')), parsed(null, 'Type', 1));
eq(type(mock('Type@999')), parsed(null, 'Type', 999));
eq(type(mock('Type@X')), parsed(null, 'Type@X', null));
eq(type(mock('package/Type@1')), parsed('package', 'Type', 1));
eq(type(mock('package////@3@2@1@1')), parsed('package', '///@3@2@1', 1));

eq(type(Identity(42)), parsed('my-package', 'Identity', null));
eq(type(Identity), named('Function'));
eq(type(Identity.prototype), named('Object'));
eq(type(Nothing), parsed('my-package', 'Maybe', 1));
eq(type(Just(0)), parsed('my-package', 'Maybe', 1));
eq(type(Nothing.constructor), named('Object'));

eq(type(false), named('Boolean'));
eq(type(0), named('Number'));
eq(type(''), named('String'));

eq(type(new Boolean(false)), named('Boolean'));
eq(type(new Number(0)), named('Number'));
eq(type(new String('')), named('String'));
});

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