stdlib: Update uri_string documentation (HTML 5.2)

- Original link to HTML 5.0 specification was broken as the
  document was moved when later revisions were released.
- Form-urlencoded query string handling conforms to the
  HTML 5.2 specification that references WHATWG URL
  (10 Jan 2018).
- HTML 5.2 does not specify handling of non-UTF-8
  form-urlencoded query strings, but it is still supported
  as described in HTML 5.0.

Change-Id: I44603bb501530b16651ecbb9a26ea64e119f83d9

2 files changed, 19 insertions, 11 deletions

diff --git a/lib/stdlib/doc/src/uri_string.xml b/lib/stdlib/doc/src/uri_string.xml
index 6b52ffdd4d..88d4600611 100644
--- a/lib/stdlib/doc/src/uri_string.xml
+++ b/lib/stdlib/doc/src/uri_string.xml
@@ -32,7 +32,11 @@
   <description>
     <p>This module contains functions for parsing and handling URIs
     (<url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>) and
-    form-urlencoded query strings (<url href="https://www.w3.org/TR/html5/forms.html">HTML5</url>).
+    form-urlencoded query strings (<url href="https://www.w3.org/TR/html52/">HTML 5.2</url>).
+    </p>
+    <p>
+    Parsing and serializing non-UTF-8 form-urlencoded query strings are also supported
+    (<url href="https://www.w3.org/TR/html50/">HTML 5.0</url>).
     </p>
     <p>A URI is an identifier consisting of a sequence of characters   matching the syntax
     rule named <em>URI</em> in <url href="https://www.ietf.org/rfc/rfc3986.txt">RFC 3986</url>.
@@ -152,8 +156,10 @@
         <p>Composes a form-urlencoded <c><anno>QueryString</anno></c> based on a
 	<c><anno>QueryList</anno></c>, a list of non-percent-encoded key-value pairs.
         Form-urlencoding is defined in section
-	4.10.22.6 of the <url href="https://www.w3.org/TR/html5/forms.html">HTML5</url>
-	specification.
+	4.10.21.6 of the <url href="https://www.w3.org/TR/html52/">HTML 5.2</url>
+	specification and in section 4.10.22.6 of the
+	<url href="https://www.w3.org/TR/html50/">HTML 5.0</url> specification for
+	non-UTF-8 encodings.
 	</p>
 	<p>See also the opposite operation <seealso marker="#dissect_query/1">
 	<c>dissect_query/1</c></seealso>.
@@ -210,12 +216,11 @@
         <p>Dissects an urlencoded <c><anno>QueryString</anno></c> and returns a
 	<c><anno>QueryList</anno></c>, a list of non-percent-encoded key-value pairs.
         Form-urlencoding is defined in section
-	4.10.22.6 of the <url href="https://www.w3.org/TR/html5/forms.html">HTML5</url>
-	specification.
+	4.10.21.6 of the <url href="https://www.w3.org/TR/html52/">HTML 5.2</url>
+	specification and in section 4.10.22.6 of the
+	<url href="https://www.w3.org/TR/html50/">HTML 5.0</url> specification for
+	non-UTF-8 encodings.
 	</p>
-	<p>It is not as strict for its input as the decoding algorithm defined by
-	<url href="https://www.w3.org/TR/html5/forms.html">HTML5</url>
-	and accepts all unicode characters.</p>
 	<p>See also the opposite operation <seealso marker="#compose_query/1">
 	<c>compose_query/1</c></seealso>.
 	</p>
diff --git a/lib/stdlib/src/uri_string.erl b/lib/stdlib/src/uri_string.erl
index ed3a2a10ac..28d36ea229 100644
--- a/lib/stdlib/src/uri_string.erl
+++ b/lib/stdlib/src/uri_string.erl
@@ -403,7 +403,8 @@ transcode(URIString, Options) when is_list(URIString) ->
 %%-------------------------------------------------------------------------
 %% Functions for working with the query part of a URI as a list
 %% of key/value pairs.
-%% HTML5 - 4.10.22.6 URL-encoded form data
+%% HTML 5.2 - 4.10.21.6 URL-encoded form data - WHATWG URL (10 Jan 2018) - UTF-8
+%% HTML 5.0 - 4.10.22.6 URL-encoded form data - non UTF-8
 %%-------------------------------------------------------------------------
 
 %%-------------------------------------------------------------------------
@@ -1773,7 +1774,8 @@ get_separator(_L) ->
     <<"&">>.
 
 
-%% HTML5 - 4.10.22.6 URL-encoded form data - encoding
+%% HTML 5.2 - 4.10.21.6 URL-encoded form data - WHATWG URL (10 Jan 2018) - UTF-8
+%% HTML 5.0 - 4.10.22.6 URL-encoded form data - encoding (non UTF-8)
 form_urlencode(Cs, [{encoding, latin1}]) when is_list(Cs) ->
     B = convert_to_binary(Cs, utf8, utf8),
     html5_byte_encode(base10_encode(B));
@@ -1868,7 +1870,8 @@ dissect_query_value(<<>>, IsList, Acc, Key, Value) ->
     lists:reverse([{K,V}|Acc]).
 
 
-%% Form-urldecode input based on RFC 1866 [8.2.1]
+%% HTML 5.2 - 4.10.21.6 URL-encoded form data - WHATWG URL (10 Jan 2018) - UTF-8
+%% HTML 5.0 - 4.10.22.6 URL-encoded form data - decoding (non UTF-8)
 form_urldecode(true, B) ->
     Result = base10_decode(form_urldecode(B, <<>>)),
     convert_to_list(Result, utf8);