Added YamlParser.display()

* renders events with proper tag and anchor names

server/server.nim

@@ -35,7 +35,7 @@ routes:
           output = "+STR\n"
           parser = newYamlParser()
           events = parser.parse(newStringStream(@"input"))
-        for event in events: output.add($event & "\n")
+        for event in events: output.add(parser.display(event) & "\n")
         output &= "-STR"
         resultNode["code"] = %0
         resultNode["output"] = %output

yaml/parser.nim

@@ -1083,3 +1083,46 @@ proc anchorName*(p: YamlParser, anchor: AnchorId): string {.raises: [].} =
   for representation, value in p.anchors:
     if value == anchor: return representation
   return ""
+
+proc renderAttrs(p: YamlParser, tag: TagId, anchor: AnchorId): string =
+  result = ""
+  case tag
+  of yTagQuestionmark: discard
+  of yTagExclamationmark: result = " !"
+  else:
+    let tagUri = p.taglib.uri(tag)
+    if tagUri.startsWith(yamlTagRepositoryPrefix):
+      result = " !!" & tagUri[yamlTagRepositoryPrefix.len..^1]
+    else:
+      result = " !<" & tagUri & ">"
+
+proc display*(p: YamlParser, event: YamlStreamEvent): string
+    {.raises: [KeyError].} =
+  ## Generate a representation of the given event with proper visualization of
+  ## anchor and tag (if any). The generated representation is conformant to the
+  ## format used in the yaml test suite.
+  ##
+  ## This proc is an informed version of ``$`` on ``YamlStreamEvent`` which can
+  ## properly display the anchor and tag name as it occurs in the input.
+  ## However, it shall only be used while using the streaming API because after
+  ## finishing the parsing of a document, the parser drops all information about
+  ## anchor and tag names.
+  case event.kind
+  of yamlEndMap: result = "-MAP"
+  of yamlEndSeq: result = "-SEQ"
+  of yamlStartDoc: result = "+DOC"
+  of yamlEndDoc: result = "-DOC"
+  of yamlStartMap: result = "+MAP" & p.renderAttrs(event.mapTag, event.mapAnchor)
+  of yamlStartSeq: result = "+SEQ" & p.renderAttrs(event.seqTag, event.seqAnchor)
+  of yamlScalar:
+    result = "=VAL" & p.renderAttrs(event.scalarTag, event.scalarAnchor)
+    when defined(yamlScalarRepInd):
+      case event.scalarRep
+      of srPlain: result &= " :"
+      of srSingleQuoted: result &= " \'"
+      of srDoubleQuoted: result &= " \""
+      of srLiteral: result &= " |"
+      of srFolded: result &= " >"
+    else: result &= " :"
+    result &= yamlTestSuiteEscape(event.scalarContent)
+  of yamlAlias: result = "=ALI *" & p.anchorName(event.aliasTarget)

yaml/private/internal.nim

@@ -27,3 +27,12 @@ template yAssert*(e: typed) =
         except: discard
       echo "[NimYAML] Please report this bug."
       quit 1
+
+proc yamlTestSuiteEscape*(s: string): string =
+  result = ""
+  for c in s:
+    case c
+    of '\l': result.add("\\n")
+    of '\c': result.add("\\c")
+    of '\\': result.add("\\\\")
+    else: result.add(c)

yaml/stream.nim

@@ -253,19 +253,9 @@ proc renderAttrs(tag: TagId, anchor: AnchorId): string =
   else: result &= " !<" & $tag & ">"
   if anchor != yAnchorNone: result &= " &" & $anchor
 
-proc yamlEscape(s: string): string =
-  result = ""
-  for c in s:
-    case c
-    of '\l': result.add("\\n")
-    of '\c': result.add("\\c")
-    of '\\': result.add("\\\\")
-    else: result.add(c)
-
 proc `$`*(event: YamlStreamEvent): string {.raises: [].} =
   ## outputs a human-readable string describing the given event.
   ## This string is compatible to the format used in the yaml test suite.
-  result = $event.kind & '('
   case event.kind
   of yamlEndMap: result = "-MAP"
   of yamlEndSeq: result = "-SEQ"
@@ -283,7 +273,7 @@ proc `$`*(event: YamlStreamEvent): string {.raises: [].} =
       of srLiteral: result &= " |"
       of srFolded: result &= " >"
     else: result &= " :"
-    result &= yamlEscape(event.scalarContent)
+    result &= yamlTestSuiteEscape(event.scalarContent)
   of yamlAlias: result = "=ALI *" & $event.aliasTarget
 
 proc tag*(event: YamlStreamEvent): TagId {.raises: [FieldError].} =