Implemented anchors and aliases

private/lex.nim

@@ -181,6 +181,8 @@ proc plainScalarPart[T](lex: YamlLexer): bool
 proc blockScalarHeader[T](lex: YamlLexer): bool
 proc blockScalar[T](lex: YamlLexer): bool
 proc tagHandle[T](lex: YamlLexer): bool
+proc anchor[T](lex: YamlLexer): bool
+proc alias[T](lex: YamlLexer): bool
 proc streamEnd(lex: YamlLexer): bool
 
 # implementation
@@ -589,6 +591,15 @@ proc insideLine[T](lex: YamlLexer): bool =
   of '!':
     lex.nextState = tagHandle[T]
     result = false
+  of '&':
+    lex.nextState = anchor[T]
+    result = false
+  of '*':
+    lex.nextState = alias[T]
+    result = false
+  of '@', '`':
+    raise generateError[T](lex,
+        "Reserved characters cannot start a plain scalar")
   else:
     lex.nextState = plainScalarPart[T]
     result = false
@@ -758,6 +769,29 @@ proc tagHandle[T](lex: YamlLexer): bool =
   else: lex.nextState = insideLine[T]
   result = true
 
+proc anchorName[T](lex: YamlLexer) =
+  debug("lex: anchorName")
+  while true:
+    lex.advance(T)
+    case lex.c
+    of spaceOrLineEnd, '[', ']', '{', '}', ',': break
+    else: lex.buf.add(lex.c)
+  while lex.c in space: lex.advance(T)
+  if lex.c in lineEnd: lex.nextState = expectLineEnd[T]
+  else: lex.nextState = insideLine[T]
+
+proc anchor[T](lex: YamlLexer): bool =
+  debug("lex: anchor")
+  anchorName[T](lex)
+  lex.cur = ltAnchor
+  result = true
+
+proc alias[T](lex: YamlLexer): bool =
+  debug("lex: alias")
+  anchorName[T](lex)
+  lex.cur = ltAlias
+  result = true
+
 proc streamEnd(lex: YamlLexer): bool =
   debug("lex: streamEnd")
   lex.cur = ltStreamEnd

test/tlex.nim

@@ -4,7 +4,8 @@ import unittest, strutils
 
 const tokensWithValue =
     {ltScalarPart, ltQuotedScalar, ltYamlVersion, ltTagShorthand, ltTagUri,
-     ltUnknownDirective, ltUnknownDirectiveParams, ltLiteralTag}
+     ltUnknownDirective, ltUnknownDirectiveParams, ltLiteralTag, ltAnchor,
+     ltAlias}
 
 type
   TokenWithValue = object
@@ -125,6 +126,8 @@ proc th(handle, suffix: string): TokenWithValue =
   TokenWithValue(kind: ltTagHandle, handle: handle, suffix: suffix)
 proc lt(v: string): TokenWithValue =
   TokenWithValue(kind: ltLiteralTag, value: v)
+proc an(v: string): TokenWithValue = TokenWithValue(kind: ltAnchor, value: v)
+proc al(v: string): TokenWithValue = TokenWithValue(kind: ltAlias, value: v)
 
 suite "Lexer":
   test "Empty document":
@@ -202,4 +205,9 @@ suite "Lexer":
 
   test "Literal tag handle":
     assertEquals("!<tag:yaml.org,2002:str> string", i(0),
-        lt("tag:yaml.org,2002:str"), sp("string"), se())
+        lt("tag:yaml.org,2002:str"), sp("string"), se())
+
+  test "Anchors and aliases":
+    assertEquals("&a foo: {&b b: *a, *b : c}", i(0), an("a"), sp("foo"), mv(),
+        oo(), an("b"), sp("b"), mv(), al("a"), c(), al("b"), mv(), sp("c"),
+        oc(), se())