Fix vCard 3 REV and KEY value handling

Bring the remaining vCard 3 REV and KEY behavior into line with RFC
2426.

For REV, serialize VALUE=date using the date form instead of incorrectly
emitting VALUE=date-time with a timestamp payload.

For KEY, stop defaulting constructed values to VALUE=uri. The vCard 3
specification defines KEY as binary by default and allows it to be reset
to text, but not to uri. Tighten both construction and parsing
accordingly: reject VALUE=uri for KEY, enforce the relationship between
VALUE=binary and ENCODING=b, and reject VALUE=text when ENCODING=b is
present.

Update the regression coverage to reflect the spec boundary: PHOTO,
LOGO, and SOUND may round-trip as uris; KEY may contain text that looks
like a URI; KEY does not allow VALUE=uri; and vCard 3 KEY parameters
still require name=value syntax.

AI-Assisted: yes
AI-Tool: OpenAI Codex / gpt-5.4 xhigh

src/vcard/vcard3.nim

@@ -609,11 +609,22 @@ func newVC3_Class*(value: string, group = none[string]()): VC3_Class =
 
 func newVC3_Key*(
   value: string,
-  valueType = some("uri"),
+  valueType = none[string](),
   keyType = none[string](),
   isInline = false,
   group = none[string]()): VC3_Key =
 
+  if valueType.isSome:
+    if valueType.get == $vtUri:
+      raise newException(ValueError,
+        "KEY content does not support the '" & $vtUri & "' value type")
+    elif valueType.get == $vtBinary and not isInline:
+      raise newException(ValueError,
+        "KEY content with VALUE=binary must also specify ENCODING=b")
+    elif valueType.get == $vtText and isInline:
+      raise newException(ValueError,
+        "KEY content with ENCODING=b cannot use VALUE=text")
+
   return assignFields(
     VC3_Key(name: $pnKey, binaryType: keyType),
     value, valueType, keyType, isInline, group)
@@ -855,7 +866,7 @@ proc serialize(r: VC3_Rev): string =
   if r.valueType.isSome and r.valueType.get == "date-time":
     result &= ";VALUE=date-time:" & r.value.format(DATETIME_FMT)
   elif r.valueType.isSome and r.valueType.get == "date":
-    result &= ";VALUE=date-time:" & r.value.format(DATETIME_FMT)
+    result &= ";VALUE=date:" & r.value.format(DATE_FMT)
   else:
     result &= r.value.format(DATETIME_FMT)
 
@@ -1264,11 +1275,20 @@ proc parseContentLines*(p: var VCardParser): seq[VC3_Property] =
       result.add(newVC3_Class(group = group, value = p.readValue))
 
     of $pnKey:
+      let valueType = params.getSingleValue("VALUE")
       let isInline = params.existsWithValue("ENCODING", "B")
+      if valueType.isSome:
+        if valueType.get == $vtUri:
+          p.error("invalid VALUE for KEY content. " &
+                  "Expected '" & $vtText & "' or '" & $vtBinary & "'")
+        elif valueType.get == $vtBinary and not isInline:
+          p.error("KEY content with VALUE=binary must also specify ENCODING=b")
+        elif valueType.get == $vtText and isInline:
+          p.error("KEY content with ENCODING=b cannot use VALUE=text")
       result.add(newVC3_Key(
         group = group,
         value = p.readBinaryValue(isInline, "KEY"),
-        valueType = params.getSingleValue("VALUE"),
+        valueType = valueType,
         keyType = params.getSingleValue("TYPE"),
         isInline = isInline))
 

tests/tvcard3.nim

@@ -182,21 +182,44 @@ suite "vcard/vcard3":
       serialized.contains("SOUND;ENCODING=b;TYPE=WAVE:" & payload)
       serialized.contains("KEY;ENCODING=b;TYPE=PGP:" & payload)
 
-  test "spec: uri-backed binary properties round-trip as uris":
+  test "spec: PHOTO, LOGO, and SOUND may round-trip as uris":
     let serialized = $parseSingleVCard3(vcard3Doc(
       "VERSION:3.0",
       "FN:John Smith",
       "N:Smith;John;;;",
       "PHOTO;VALUE=uri:http://example.test/photo.jpg",
       "LOGO;VALUE=uri:http://example.test/logo.gif",
-      "SOUND;VALUE=uri:http://example.test/sound.wav",
-      "KEY;VALUE=uri:http://example.test/key.asc"))
+      "SOUND;VALUE=uri:http://example.test/sound.wav"))
 
     check:
       serialized.contains("PHOTO;VALUE=uri:http://example.test/photo.jpg")
       serialized.contains("LOGO;VALUE=uri:http://example.test/logo.gif")
       serialized.contains("SOUND;VALUE=uri:http://example.test/sound.wav")
-      serialized.contains("KEY;VALUE=uri:http://example.test/key.asc")
+
+  test "spec: KEY does not allow uri values":
+    expect(VCardParsingError):
+      discard parseVCards(vcard3Doc(
+        "VERSION:3.0",
+        "FN:John Smith",
+        "N:Smith;John;;;",
+        "KEY;VALUE=uri:http://example.test/key.asc"))
+
+  test "spec: KEY may contain text values that look like uris":
+    let serialized = $parseSingleVCard3(vcard3Doc(
+      "VERSION:3.0",
+      "FN:John Smith",
+      "N:Smith;John;;;",
+      "KEY;TYPE=PGP:http://example.test/key.pgp"))
+
+    check serialized.contains("KEY;TYPE=PGP:http://example.test/key.pgp")
+
+  test "spec: KEY parameters must use name=value syntax in vCard 3":
+    expect(VCardParsingError):
+      discard parseVCards(vcard3Doc(
+        "VERSION:3.0",
+        "FN:John Smith",
+        "N:Smith;John;;;",
+        "KEY;PGP:http://example.test/key.pgp"))
 
   test "spec: quoted parameter values are accepted":
     let parsed = parseSingleVCard3(vcard3Doc(