Added support for optionally matching keys of an object

balena-io-modules · Jun 11, 2016 · 1fb436e · 1fb436e
1 parent bff277a
commit 1fb436e
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Showing 5 changed files with 28 additions and 6 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,4 @@
+* Added support for optionally matching keys of an object, eg `@{ foo?: true }`
 * Added support for matching some keys of an object against corresponding rules,
 	eg `%{ foo: FooRule }`
 * Added support for matching all keys of an object against corresponding rules,

diff --git a/lib/ometajs/core.js b/lib/ometajs/core.js
@@ -694,12 +694,23 @@
 			var ruleKeys = Object.keys(x),
 				result = {};
 			if(matchAllInput) {
-				this._pred(ruleKeys.length === Object.keys(v).length);
+				var inputLength = Object.keys(v).length;
+				this._pred(ruleKeys.length >= inputLength);
 			}
 			for(var i = 0; i < ruleKeys.length; i++) {
-				var key = ruleKeys[i];
-				this._pred(v.hasOwnProperty(key));
-				result[key] = this._applyWithArgs('applyFn', x[key], v[key]);
+				var key = ruleKeys[i],
+					exists = v.hasOwnProperty(key),
+					ruleFn = x[key][0],
+					required = x[key][1];
+				if(required) {
+					this._pred(exists);
+				} else if(!exists) {
+					continue;
+				}
+				result[key] = this._applyWithArgs('applyFn', ruleFn, v[key]);
+			}
+			if(matchAllInput) {
+				this._pred(Object.keys(result).length === inputLength);
 			}
 			return v;
 		},

diff --git a/src/bs-ometa-compiler.ometajs b/src/bs-ometa-compiler.ometajs
@@ -64,7 +64,10 @@ export ometa BSOMetaParser {
   objectRules    = {{}}:o
                    (objectRule:x ',' -> x)*:a
                    objectRule:x                                        -> a.concat([x]),
-  objectRule     = BSJSParser.jsonPropName:n ":" expr:x                -> [n, x],
+  objectRule     = BSJSParser.jsonPropName:n
+                   ( "?" -> false
+                   |     -> true
+                   ):required ":" expr:x                               -> [n, x, required],
   param          = ":" name:n                                          -> n,
   ruleName       = name
                  | spaces tsString,
@@ -109,6 +112,8 @@ export ometa BSOMetaTranslator {
   Lookahead  transFn:x                     -> ['this._lookahead(',     x, ')']                                     .join(''),
   Object     [ ( [ string:key
                    transFn:x
+                   (true|false):required
+                   {['[', x, ',', required, ']'].join('')}:x
                  ]
                  -> [JSON.stringify(key), x].join(':')
                )+:o

diff --git a/test/files/simple.ometajs b/test/files/simple.ometajs
@@ -35,4 +35,8 @@ export ometa Simple {
 			%{ 'simple': true, 'simpler': true }
 			-> 'should fail'
 		|	-> 'ok'
+	,
+	ObjectRulesMatchOptional =
+		@{ 'simple': true, 'simpler'?: true }
+		-> 'ok'
 }
diff --git a/test/unit/api-test.js b/test/unit/api-test.js
@@ -25,7 +25,8 @@ var testMatches = {
 	ObjectRulesMatchAll1: { 'simple': true },
 	ObjectRulesMatchAll2: { 'simple': true, 'simpler': true },
 	ObjectRulesMatchPartial1: { 'simple': true, 'simpler': true },
-	ObjectRulesMatchPartial2: { 'simple': true }
+	ObjectRulesMatchPartial2: { 'simple': true },
+	ObjectRulesMatchOptional: { 'simple': true }
 };
 
 var runTests = function(test, grammar) {