Apply suggestions from code review

Author: eemeli

spec/formatting.md

@@ -260,8 +260,10 @@ the following steps are taken:
 
 3. Perform _option resolution_.
 
-4. Determine the **_<dfn>function context</dfn>_** for calling the function implementation.
-   This includes:
+4. Determine the _function context_ for calling the _function handler_.
+
+   The **_<dfn>function context</dfn>_** contains the context necessary for
+   the _function handler_ to resolve the _expression_. This includes:
 
    - The current _locale_,
      potentially including a fallback chain of locales.

spec/u-namespace.md

@@ -27,18 +27,20 @@ language tags,
 or an implementation-defined list of such tags.
 
 Replaces the _locale_ defined in the _function context_ for this _expression_.
-The value is ignored when set on _markup_.
+
+If this option is set on _markup_, a _Bad Option_ error is emitted
+and the value of the `u:locale` option is ignored.
 
 During processing, the `u:locale` option
-is always removed from the resolved mapping of _options_.
+MUST be removed from the resolved mapping of _options_
+before calling the _function handler_.
 
 Values matching the following ABNF are always accepted:
 ```abnf
-u-locale-option = langtag *(o "," o langtag)
+u-locale-option = unicode_bcp47_locale_id *(o "," o unicode_bcp47_locale_id)
 ```
-using `langtag` as defined in [BCP 47](https://www.rfc-editor.org/rfc/bcp/bcp47.txt).
-Note that `langtag` is the rule for "normal language tags",
-and does not include private-use or grandfathered tags.
+using `unicode_bcp47_locale_id` as defined for
+[Unicode Locale Identifier](https://cldr-smoke.unicode.org/spec/main/ldml/tr35.html#unicode_bcp47_locale_id).
 
 Implementations MAY support additional language tags,
 such as private-use or grandfathered tags,
@@ -53,10 +55,13 @@ and the value of the `u:locale` option is ignored.
 
 Replaces the base directionality defined in
 the _function context_ for this _expression_.
-The value is ignored when set on _markup_.
+
+If this option is set on _markup_, a _Bad Option_ error is emitted
+and the value of the `u:dir` option is ignored.
 
 During processing, the `u:dir` option
-is always removed from the resolved mapping of _options_.
+MUST be removed from the resolved mapping of _options_
+before calling the _function handler_.
 
 Accepts the following string values:
 - `ltr`: left-to-right directionality

test/tests/u-options.json

@@ -7,7 +7,7 @@
   },
   "tests": [
     {
-      "src": "{#tag u:id=x u:dir=rtl u:locale=ar}content{/ns:tag u:id=x}",
+      "src": "{#tag u:id=x}content{/ns:tag u:id=x}",
       "exp": "content",
       "expParts": [
         {
@@ -28,6 +28,27 @@
         }
       ]
     },
+    {
+      "src": "{#tag u:dir=rtl u:locale=ar}content{/ns:tag}",
+      "exp": "content",
+      "expErrors": [{ "type": "bad-option" }, { "type": "bad-option" }],
+      "expParts": [
+        {
+          "type": "markup",
+          "kind": "open",
+          "name": "tag"
+        },
+        {
+          "type": "literal",
+          "value": "content"
+        },
+        {
+          "type": "markup",
+          "kind": "close",
+          "name": "tag"
+        }
+      ]
+    },
     {
       "src": "hello {4.2 :number u:locale=fr}",
       "exp": "hello 4,2"