Allow @container: @set on @type

This change addresses w3c/json-ld-syntax#34

Author: kazarena

ld/api_compact.go

@@ -14,7 +14,9 @@
 
 package ld
 
-import "sort"
+import (
+	"sort"
+)
 
 // Compact operation compacts the given input using the context
 // according to the steps in the Compaction Algorithm:
@@ -98,6 +100,9 @@ func (api *JsonLdApi) Compact(activeCtx *Context, activeProperty string, element
 			expandedValue := elem[expandedProperty]
 
 			if expandedProperty == "@id" || expandedProperty == "@type" {
+
+				alias := activeCtx.CompactIri(expandedProperty, nil, true, false)
+
 				var compactedValue interface{}
 
 				compactedValues := make([]interface{}, 0)
@@ -107,16 +112,16 @@ func (api *JsonLdApi) Compact(activeCtx *Context, activeProperty string, element
 					compactedValues = append(compactedValues, cv)
 				}
 
-				if len(compactedValues) == 1 {
+				cont := activeCtx.GetContainer(alias)
+				isTypeContainer := expandedProperty == "@type" && (len(cont) > 0 && cont[0] == "@set")
+				if len(compactedValues) == 1 && (!activeCtx.processingMode(1.1) || !isTypeContainer) {
 					compactedValue = compactedValues[0]
 				} else {
 					compactedValue = compactedValues
 				}
-
-				alias := activeCtx.CompactIri(expandedProperty, nil, true, false)
+				
 				compValArray, isArray := compactedValue.([]interface{})
-				AddValue(result, alias, compactedValue, isArray && len(compValArray) == 0, true)
-
+				AddValue(result, alias, compactedValue, isArray && (len(compValArray) == 0 || isTypeContainer), true)
 				continue
 			}
 

ld/context.go

@@ -340,11 +340,6 @@ func (c *Context) createTermDefinition(context map[string]interface{}, term stri
 
 	defined[term] = false
 
-	if IsKeyword(term) {
-		return NewJsonLdError(KeywordRedefinition, term)
-	}
-
-	delete(c.termDefinitions, term)
 	value := context[term]
 	mapValue, isMap := value.(map[string]interface{})
 	idValue, hasID := mapValue["@id"]
@@ -365,6 +360,18 @@ func (c *Context) createTermDefinition(context map[string]interface{}, term stri
 		return NewJsonLdError(InvalidTermDefinition, value)
 	}
 
+	if IsKeyword(term) {
+		vmap, isMap := value.(map[string]interface{})
+		isTypeContainerAsSet := term == "@type" && isMap && vmap["@container"] == "@set"
+		if c.processingMode(1.1) && isTypeContainerAsSet {
+			// this is the only case were redefining a keyword is allowed
+		} else {
+			return NewJsonLdError(KeywordRedefinition, term)
+		}
+	}
+
+	delete(c.termDefinitions, term)
+
 	// casting the value so it doesn't have to be done below everytime
 	val := mapValue
 
@@ -468,7 +475,7 @@ func (c *Context) createTermDefinition(context map[string]interface{}, term stri
 			// 15)
 		} else if vocabValue, containsVocab := c.values["@vocab"]; containsVocab {
 			definition["@id"] = vocabValue.(string) + term
-		} else {
+		} else if term != "@type" {
 			return NewJsonLdError(InvalidIRIMapping, "relative term definition without vocab mapping")
 		}
 	}
@@ -596,6 +603,10 @@ func (c *Context) createTermDefinition(context map[string]interface{}, term stri
 		}
 
 		definition["@container"] = container
+
+		if term == "@type" {
+			definition["@id"] = "@type"
+		}
 	}
 
 	// scoped contexts