1 files changed, 41 insertions, 0 deletions
diff --git a/lib/core/hotcodereloading.nim b/lib/core/hotcodereloading.nim
new file mode 100644
index 000000000..3a876885c
--- /dev/null
+++ b/lib/core/hotcodereloading.nim
@@ -0,0 +1,41 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2019 Nim contributors
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## Unstable API.
+
+when defined(hotcodereloading):
+  import
+    std/macros
+
+  template beforeCodeReload*(body: untyped) =
+    hcrAddEventHandler(true, proc = body) {.executeOnReload.}
+
+  template afterCodeReload*(body: untyped) =
+    hcrAddEventHandler(false, proc = body) {.executeOnReload.}
+
+  macro hasModuleChanged*(module: typed): untyped =
+    if module.kind != nnkSym or module.symKind != nskModule:
+      error "hasModuleChanged expects a module symbol", module
+    return newCall(bindSym"hcrHasModuleChanged", newLit(module.signatureHash))
+
+  proc hasAnyModuleChanged*(): bool = hcrReloadNeeded()
+
+  when not defined(js):
+    template performCodeReload* =
+      when isMainModule:
+        {.warning: "Code residing in the main module will not be changed from calling a code-reload".}
+      hcrPerformCodeReload()
+  else:
+    template performCodeReload* = discard
+else:
+  template beforeCodeReload*(body: untyped) = discard
+  template afterCodeReload*(body: untyped) = discard
+  template hasModuleChanged*(module: typed): bool = false
+  proc hasAnyModuleChanged*(): bool = false
+  template performCodeReload*() = discard