jjson: added the %* macro inspired from json.nim

karax/jjson.nim

@@ -19,9 +19,12 @@ proc newJsonNode*(fields: varargs[(cstring, JsonNode)]): JsonNode =
 proc newJObject*(): JsonNode =
   result = JsonNode()
 
+proc newJArray*(elements: varargs[JsonNode]): JsonNode {.importcpp: "#".}
+
 proc newJNull*(): JsonNode = nil
 
 template `%`*(x: typed): JsonNode = cast[JsonNode](x)
+template `%`*(x: string): JsonNode = cast[JsonNode](cstring x)
 
 proc getNum*(x: JsonNode): int {.importcpp: "#".}
 
@@ -31,3 +34,34 @@ proc getFNum*(x: JsonNode): cstring {.importcpp: "#".}
 
 iterator items*(x: JsonNode): JsonNode =
   for i in 0..<len(x): yield x[i]
+
+import macros
+
+proc toJson(x: NimNode): NimNode {.compiletime.} =
+  case x.kind
+  of nnkBracket:
+    result = newCall(bindSym"newJArray")
+    for i in 0 ..< x.len:
+      result.add(toJson(x[i]))
+  of nnkTableConstr:
+    result = newCall(bindSym"newJsonNode")
+    for i in 0 ..< x.len:
+      x[i].expectKind nnkExprColonExpr
+      let key = x[i][0]
+      let a = if x[i].kind in {nnkIdent, nnkSym, nnkAccQuoted}:
+                newLit($key)
+              else:
+                key
+      result.add newTree(nnkPar, newCall(bindSym"cstring", a), toJson(x[i][1]))
+  of nnkCurly:
+    x.expectLen(0)
+    result = newCall(bindSym"newJObject")
+  of nnkNilLit:
+    result = newCall(bindSym"newJNull")
+  else:
+    result = newCall(bindSym"%", x)
+
+macro `%*`*(x: untyped): untyped =
+  ## Convert an expression to a JsonNode directly, without having to specify
+  ## `%` for every element.
+  result = toJson(x)