adds EAV helpers

mod.ts

@@ -0,0 +1,51 @@
+export type Result<
+  T,
+  E extends Error = Error,
+> = T | E;
+
+export type CustomError<M extends string> = Error & { message: M };
+
+export function addMsg<M extends string, E extends Error>(
+  error: E,
+  message: M,
+): CustomError<`${M}\n${string}`> {
+  return Object.assign(error, {
+    message: message +
+      `\n${error.message.split("\n").map((line) => "  " + line).join("\n")}`,
+  }) as CustomError<`${M}\n${string}`>;
+}
+
+export function Err<M extends string>(message: M): CustomError<M> {
+  return new Error(message) as CustomError<M>;
+}
+
+export function Try<T extends (...args: any[]) => any>(
+  func: T,
+): (...args: Parameters<T>) => ReturnType<T> | Error {
+  return (...args: Parameters<T>) => {
+    try {
+      return func(...args);
+    } catch (error) {
+      return error;
+    }
+  };
+}
+
+// deno-lint-ignore no-explicit-any
+export function isErr<T extends Error>(value: Result<any>): value is T {
+  return value instanceof Error;
+}
+
+export function Ok<T>(value: Result<T>): T | null {
+  if (value instanceof Error) {
+    return null;
+  }
+  return value;
+}
+
+export function Unwrap<T>(value: Result<T>): T {
+  if (value instanceof Error) {
+    throw value;
+  }
+  return value;
+}