feat(logic): introduce path-satisfies

src/_path-satisfies.scss

@@ -0,0 +1,21 @@
+@import 'path';
+
+/// Returns `true` if the specified object property at given path satisfies the
+/// given predicate; `false` otherwise.
+///
+/// @group logic
+/// @param {Function} pred
+/// @param {List} path The path to use.
+/// @param {Object} map The map to retrieve the nested property from.
+/// @return {*} The data at `path` of the supplied object or null.
+///
+/// @example scss - path
+///
+///   @function is-positive($n) { @return $n > 0; }
+///   $value-is-pos: path-satisfies(is-positive, ('a', 'b'), (a: (b: 2)));
+///   @debug $value-is-pos; //=> true
+
+@function path-satisfies($pred, $path, $map) {
+    $value: path($path, $map);
+    @return if($value, call(get-function($pred), $value), false);
+}

test/_path-satisfies.spec.scss

@@ -0,0 +1,94 @@
+@import 'true';
+@import '../src/path-satisfies';
+
+@function __path-satisfies-spec-is-positive($n) {
+    @return $n > 0;
+}
+
+@function __path-satisfies-spec-has-key-y($map) {
+    @return map-has-key($map, 'y');
+}
+
+@function __path-satisfies-spec-is-map($map) {
+    @return type-of($map) == 'map';
+}
+
+@include describe('path-satisfies [function]') {
+    @include it(
+        'returns true if the specified object path satisfies the given predicate'
+    ) {
+        @include assert-equal(
+            path-satisfies(
+                __path-satisfies-spec-is-positive,
+                ('x', 2, 'y'),
+                (
+                    x: (
+                        (y: -1),
+                        (y: 1),
+                    ),
+                )
+            ),
+            true
+        );
+    }
+
+    @include it('returns false if the specified path does not exist') {
+        @include assert-equal(
+            path-satisfies(
+                __path-satisfies-spec-is-positive,
+                ('x', 'y'),
+                (
+                    x: (
+                        z: 42,
+                    ),
+                )
+            ),
+            false
+        );
+    }
+
+    @include it('handles empty paths by applying pred to data: positive') {
+        @include assert-equal(
+            path-satisfies(
+                __path-satisfies-spec-is-map,
+                (),
+                (
+                    x: (
+                        z: 42,
+                    ),
+                )
+            ),
+            true
+        );
+    }
+
+    @include it('handles empty paths by applying pred to data: negative') {
+        @include assert-equal(
+            path-satisfies(
+                __path-satisfies-spec-has-key-y,
+                (),
+                (
+                    x: (
+                        z: 42,
+                    ),
+                )
+            ),
+            false
+        );
+    }
+
+    @include it('returns false otherwise') {
+        @include assert-equal(
+            path-satisfies(
+                __path-satisfies-spec-is-positive,
+                ('x', 'y'),
+                (
+                    x: (
+                        y: 0,
+                    ),
+                )
+            ),
+            false
+        );
+    }
+}