Accept https:// JSON Schema URIs (#98)

The JSON Schema spec calls $schema an identifier, not a literal URL, and
json-schema.org now serves both http:// and https:// forms. Tools commonly
emit https://, but `schema_module/2` and `remote_schema/1` only matched the
canonical http:// prefix and raised UnsupportedSchemaVersionError on any
https:// input.

Normalize https://json-schema.org/... to http://json-schema.org/... at the
top of both functions. No behavioural change for any other input.

Closes #97

Author: elias-ba

lib/ex_json_schema/schema.ex

@@ -163,6 +163,10 @@ defmodule ExJsonSchema.Schema do
   end
 
   defp schema_module(schema_url, default \\ Draft7)
+
+  defp schema_module("https://json-schema.org/" <> rest, default),
+    do: schema_module("http://json-schema.org/" <> rest, default)
+
   defp schema_module(@draft4_schema_url <> _, _), do: Draft4
   defp schema_module(@draft6_schema_url <> _, _), do: Draft6
   defp schema_module(@draft7_schema_url <> _, _), do: Draft7
@@ -257,6 +261,9 @@ defmodule ExJsonSchema.Schema do
   end
 
   @spec remote_schema(String.t()) :: ExJsonSchema.object()
+  defp remote_schema("https://json-schema.org/" <> rest),
+    do: remote_schema("http://json-schema.org/" <> rest)
+
   defp remote_schema(@current_draft_schema_url <> _), do: Draft7.schema()
   defp remote_schema(@draft4_schema_url <> _), do: Draft4.schema()
   defp remote_schema(@draft6_schema_url <> _), do: Draft6.schema()

test/ex_json_schema/schema_test.exs

@@ -31,6 +31,20 @@ defmodule ExJsonSchema.SchemaTest do
     assert resolve(schema) == %ExJsonSchema.Schema.Root{refs: %{}, schema: schema, version: 7}
   end
 
+  test "accepts both http:// and https:// forms of the JSON Schema URI" do
+    http_schema = %{"$schema" => "http://json-schema.org/draft-07/schema#"}
+    https_schema = %{"$schema" => "https://json-schema.org/draft-07/schema#"}
+
+    assert resolve(http_schema).version == 7
+    assert resolve(https_schema).version == 7
+
+    http_draft6 = %{"$schema" => "http://json-schema.org/draft-06/schema#"}
+    https_draft6 = %{"$schema" => "https://json-schema.org/draft-06/schema#"}
+
+    assert resolve(http_draft6).version == 6
+    assert resolve(https_draft6).version == 6
+  end
+
   test "schema is validated against its meta-schema" do
     schema = %{"properties" => "foo"}