Consider @preserve when compacting term values, as required for json-ld/json-ld.org#496.

Author: gkellogg

example-files/issue-496.rb

@@ -0,0 +1,23 @@
+require 'pp'
+require 'linkeddata'
+
+input = JSON.parse %({
+  "@context": {
+    "schema": "http://schema.org/",
+    "name": "schema:name",
+    "url": {"@id": "schema:url", "@type": "schema:URL"}
+  },
+  "name": "Jane Doe"
+})
+
+frame = JSON.parse %({
+  "@context": {
+    "schema": "http://schema.org/",
+    "name": "schema:name",
+    "url": { "@id": "schema:url", "@type": "schema:URL"}
+  },
+  "name": {},
+  "url": {"@default": {"@value": "http://example.com", "@type": "schema:URL"}}
+})
+
+pp JSON::LD::API.frame(input, frame, logger: Logger.new(STDERR))

example-files/issue-499-frame.json

@@ -0,0 +1,13 @@
+{"@context": ["http://schema.org", {
+    "maintainer": {"@type": "@id"}
+  }],
+ "@embed": "@always",
+ "author": {
+   "familyName": {},
+   "affiliation": 
+     {"@default": "@null"}
+  },
+ "maintainer": {
+   "familyName": { "@default": "none" }
+ }
+}

example-files/issue-499.json

@@ -0,0 +1,13 @@
+{
+  "@context": "http://schema.org",
+  "@type": "SoftwareSourceCode",
+  "author": 
+    {
+      "@type": "Person",
+      "givenName": "Carl",
+      "familyName": "Boettiger",
+      "email": "cboettig@gmail.com",
+      "@id": "http://orcid.org/0000-0002-1642-628X"
+    },
+  "maintainer": "http://orcid.org/0000-0002-1642-628X"
+}

example-files/mitar-in.jsonld

@@ -1,6 +1,7 @@
 {
   "@context": {
     "@vocab": "http://example/",
+    "@version": 1.1,
     "B": {"@context": {"c": "http://example.org/c"}}
   },
   "a": {

example-files/workergnome-issue-35.rb

@@ -0,0 +1,38 @@
+require 'linkeddata'
+
+graph = RDF::Graph.new
+graph << [RDF::URI("http://www.museum.com/fish"), 
+          RDF.type, 
+          RDF::URI("http://www.cidoc-crm.org/cidoc-crm/E55_Type")]
+
+unframed_json = JSON::LD::API::fromRdf(graph)
+
+
+# Using this frame:
+frame = {
+  "@context"=> [
+    "https://linked.art/ns/context/1/full.jsonld",
+    {"crm" => "http://www.cidoc-crm.org/cidoc-crm/"}
+  ]
+}
+
+# This works
+puts JSON::LD::API.frame(unframed_json, frame, base: "http://www.example.com")
+
+# But this doesn't.
+begin
+  puts JSON::LD::API.frame(unframed_json, frame)
+rescue JSON::LD::JsonLdError::InvalidBaseIRI => e
+  puts "This doesn't work: #{e}"
+end
+
+
+# But using this frame:
+frame = {
+  "@context"=> [
+    {"crm" => "http://www.cidoc-crm.org/cidoc-crm/"}
+  ]
+}
+# Both of these work
+puts JSON::LD::API.frame(unframed_json, frame, base: "http://www.example.com")
+puts JSON::LD::API.frame(unframed_json, frame)

lib/json/ld/compact.rb

@@ -101,6 +101,17 @@ def compact(element, property: nil)
             next
           end
 
+          if expanded_property == '@preserve'
+            # Compact using `property`
+            compacted_value = compact(expanded_value, property: property)
+            #log_debug("@preserve") {"compacted_value: #{compacted_value.inspect}"}
+
+            unless compacted_value.is_a?(Array) && compacted_value.empty?
+              result['@preserve'] = compacted_value
+            end
+            next
+          end
+
           if expanded_property == '@index' && context.container(property) == '@index'
             #log_debug("@index") {"drop @index"}
             next

lib/json/ld/context.rb

@@ -1023,6 +1023,9 @@ def compact_iri(iri, value: nil, vocab: nil, reverse: false, quiet: false, **opt
         containers = []
         tl, tl_value = "@language", "@null"
 
+        # If the value is a JSON Object with the key @preserve, use the value of @preserve.
+        value = value['@preserve'].first if value.is_a?(Hash) && value.has_key?('@preserve')
+
         # If the value is a JSON Object, then for the keywords @index, @id, and @type, if the value contains that keyword, append it to containers.
         %w(@index @id @type).each do |kw|
           containers << kw if value.has_key?(kw)

lib/json/ld/expand.rb

@@ -384,7 +384,6 @@ def expand_object(input, active_property, context, output_object, ordered: false
 
             # Initialize index value to the result of using this algorithm recursively, passing active context, key as active property, and index value as element.
             index_value = expand([value[k]].flatten, key, map_context, ordered: ordered)
-            #require 'byebug'; byebug
             index_value.each do |item|
               case container
               when '@index' then item[container] ||= k

lib/json/ld/frame.rb

@@ -215,11 +215,15 @@ def cleanup_preserve(input, bnodes_to_clear)
       result = case input
       when Array
         # If, after replacement, an array contains only the value null remove the value, leaving an empty array.
-        input.map {|o| cleanup_preserve(o, bnodes_to_clear)}.compact
+        v = input.map {|o| cleanup_preserve(o, bnodes_to_clear)}.compact
+
+        # If the array contains a single member, which is itself an array, use that value as the result
+         v.length == 1 && v.first.is_a?(Array) ? v.first : v
       when Hash
         output = Hash.new
         input.each do |key, value|
           if key == '@preserve'
+            #require 'byebug'; byebug
             # replace all key-value pairs where the key is @preserve with the value from the key-pair
             output = cleanup_preserve(value, bnodes_to_clear)
           elsif context.expand_iri(key) == '@id' && bnodes_to_clear.include?(value)