standard init template; macros.recordFields

std_shims.nimble

@@ -0,0 +1,11 @@
+mode = ScriptMode.Verbose
+
+packageName   = "std_shims"
+version       = "0.1.0"
+author        = "Status Research & Development GmbH"
+description   = "APIs available in the latests version of Nim, backported to older stable releases"
+license       = "Apache License 2.0"
+skipDirs      = @["tests"]
+
+requires "nim >= 0.19.0"
+

std_shims/macros_shim.nim

@@ -0,0 +1,84 @@
+import
+  macros
+
+export
+  macros
+
+type
+  FieldDescription* = object
+    name*: NimNode
+    isPublic*: bool
+    typ*: NimNode
+    pragmas*: NimNode
+
+iterator recordFields*(typeImpl: NimNode): FieldDescription =
+  # TODO: This doesn't support inheritance yet
+  let
+    objectType = typeImpl[2]
+    recList = objectType[2]
+
+  if recList.len > 0:
+    var traversalStack = @[(recList, 0)]
+    while true:
+      assert traversalStack.len > 0
+
+      let (recList, idx) = traversalStack[^1]
+      let n = recList[idx]
+      inc traversalStack[^1][1]
+
+      if idx == recList.len - 1:
+        discard traversalStack.pop
+
+      case n.kind
+      of nnkRecWhen:
+        for i in countdown(n.len - 1, 0):
+          let branch = n[i]
+          case branch.kind:
+          of nnkElifBranch:
+            traversalStack.add (branch[1], 0)
+          of nnkElse:
+            traversalStack.add (branch[0], 0)
+          else:
+            assert false
+
+        continue
+
+      of nnkRecCase:
+        assert n.len > 0
+        for i in countdown(n.len - 1, 1):
+          let branch = n[i]
+          case branch.kind
+          of nnkOfBranch:
+            traversalStack.add (branch[^1], 0)
+          of nnkElse:
+            traversalStack.add (branch[0], 0)
+          else:
+            assert false
+
+        traversalStack.add (newTree(nnkRecCase, n[0]), 0)
+        continue
+
+      of nnkIdentDefs:
+        let fieldType = n[^2]
+        for i in 0 ..< n.len - 2:
+          var field: FieldDescription
+          field.name = n[i]
+
+          if field.name.kind == nnkPostfix:
+            field.isPublic = true
+            field.name = field.name[1]
+
+          if field.name.kind == nnkPragmaExpr:
+            field.pragmas = field.name[1]
+            field.name = field.name[0]
+
+          yield field
+
+      of nnkNilLit, nnkDiscardStmt, nnkCommentStmt, nnkEmpty:
+        discard
+
+      else:
+        assert false
+
+      if traversalStack.len == 0: break
+

std_shims/objects.nim

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+template init*(lvalue: var auto, args: varargs[typed]) =
+  mixin init
+  lvalue = init(type(lvalue), args)
+