2 files changed, 29 insertions, 19 deletions

diff --git a/std/flags/mod.ts b/std/flags/mod.ts
index b334cb5b8..3afaf111f 100644
--- a/std/flags/mod.ts
+++ b/std/flags/mod.ts
@@ -51,13 +51,13 @@ export interface ArgParsingOptions {
   /** A function which is invoked with a command line parameter not defined in
    * the `options` configuration object. If the function returns `false`, the
    * unknown option is not added to `parsedArgs`. */
-  unknown?: (i: unknown) => unknown;
+  unknown?: (arg: string, key?: string, value?: unknown) => unknown;
 }
 
 interface Flags {
   bools: Record<string, boolean>;
   strings: Record<string, boolean>;
-  unknownFn: (i: unknown) => unknown;
+  unknownFn: (arg: string, key?: string, value?: unknown) => unknown;
   allBools: boolean;
 }
 
@@ -107,7 +107,7 @@ export function parse(
     default: defaults = {},
     stopEarly = false,
     string = [],
-    unknown = (i: unknown): unknown => i,
+    unknown = (i: string): unknown => i,
   }: ArgParsingOptions = {}
 ): Args {
   const flags: Flags = {
@@ -198,7 +198,7 @@ export function parse(
     arg: string | undefined = undefined
   ): void {
     if (arg && flags.unknownFn && !argDefined(key, arg)) {
-      if (flags.unknownFn(arg) === false) return;
+      if (flags.unknownFn(arg, key, val) === false) return;
     }
 
     const value = !get(flags.strings, key) && isNumber(val) ? Number(val) : val;
diff --git a/std/flags/unknown_test.ts b/std/flags/unknown_test.ts
index 90c638b67..0d822144d 100755
--- a/std/flags/unknown_test.ts
+++ b/std/flags/unknown_test.ts
@@ -4,12 +4,12 @@ import { parse } from "./mod.ts";
 
 Deno.test(function booleanAndAliasIsNotUnknown(): void {
   const unknown: unknown[] = [];
-  function unknownFn(arg: unknown): boolean {
-    unknown.push(arg);
+  function unknownFn(arg: string, k?: string, v?: unknown): boolean {
+    unknown.push({ arg, k, v });
     return false;
   }
   const aliased = ["-h", "true", "--derp", "true"];
-  const regular = ["--herp", "true", "-d", "true"];
+  const regular = ["--herp", "true", "-d", "false"];
   const opts = {
     alias: { h: "herp" },
     boolean: "h",
@@ -18,20 +18,27 @@ Deno.test(function booleanAndAliasIsNotUnknown(): void {
   parse(aliased, opts);
   parse(regular, opts);
 
-  assertEquals(unknown, ["--derp", "-d"]);
+  assertEquals(unknown, [
+    { arg: "--derp", k: "derp", v: "true" },
+    { arg: "-d", k: "d", v: "false" },
+  ]);
 });
 
 Deno.test(function flagBooleanTrueAnyDoubleHyphenArgumentIsNotUnknown(): void {
   const unknown: unknown[] = [];
-  function unknownFn(arg: unknown): boolean {
-    unknown.push(arg);
+  function unknownFn(arg: string, k?: string, v?: unknown): boolean {
+    unknown.push({ arg, k, v });
     return false;
   }
   const argv = parse(["--honk", "--tacos=good", "cow", "-p", "55"], {
     boolean: true,
     unknown: unknownFn,
   });
-  assertEquals(unknown, ["--tacos=good", "cow", "-p"]);
+  assertEquals(unknown, [
+    { arg: "--tacos=good", k: "tacos", v: "good" },
+    { arg: "cow", k: undefined, v: undefined },
+    { arg: "-p", k: "p", v: "55" },
+  ]);
   assertEquals(argv, {
     honk: true,
     _: [],
@@ -40,8 +47,8 @@ Deno.test(function flagBooleanTrueAnyDoubleHyphenArgumentIsNotUnknown(): void {
 
 Deno.test(function stringAndAliasIsNotUnkown(): void {
   const unknown: unknown[] = [];
-  function unknownFn(arg: unknown): boolean {
-    unknown.push(arg);
+  function unknownFn(arg: string, k?: string, v?: unknown): boolean {
+    unknown.push({ arg, k, v });
     return false;
   }
   const aliased = ["-h", "hello", "--derp", "goodbye"];
@@ -54,13 +61,16 @@ Deno.test(function stringAndAliasIsNotUnkown(): void {
   parse(aliased, opts);
   parse(regular, opts);
 
-  assertEquals(unknown, ["--derp", "-d"]);
+  assertEquals(unknown, [
+    { arg: "--derp", k: "derp", v: "goodbye" },
+    { arg: "-d", k: "d", v: "moon" },
+  ]);
 });
 
 Deno.test(function defaultAndAliasIsNotUnknown(): void {
   const unknown: unknown[] = [];
-  function unknownFn(arg: unknown): boolean {
-    unknown.push(arg);
+  function unknownFn(arg: string, k?: string, v?: unknown): boolean {
+    unknown.push({ arg, k, v });
     return false;
   }
   const aliased = ["-h", "hello"];
@@ -78,8 +88,8 @@ Deno.test(function defaultAndAliasIsNotUnknown(): void {
 
 Deno.test(function valueFollowingDoubleHyphenIsNotUnknown(): void {
   const unknown: unknown[] = [];
-  function unknownFn(arg: unknown): boolean {
-    unknown.push(arg);
+  function unknownFn(arg: string, k?: string, v?: unknown): boolean {
+    unknown.push({ arg, k, v });
     return false;
   }
   const aliased = ["--bad", "--", "good", "arg"];
@@ -89,7 +99,7 @@ Deno.test(function valueFollowingDoubleHyphenIsNotUnknown(): void {
   };
   const argv = parse(aliased, opts);
 
-  assertEquals(unknown, ["--bad"]);
+  assertEquals(unknown, [{ arg: "--bad", k: "bad", v: true }]);
   assertEquals(argv, {
     "--": ["good", "arg"],
     _: [],