feat: allow first arg in test step to be a function (#17096)

cli/js/40_testing.js

@@ -1265,10 +1265,10 @@
        */
       origin: desc.origin,
       /**
-       * @param nameOrTestDefinition {string | TestStepDefinition}
-       * @param fn {(t: TestContext) => void | Promise<void>}
+       * @param nameOrFnOrOptions {string | TestStepDefinition | ((t: TestContext) => void | Promise<void>)}
+       * @param maybeFn {((t: TestContext) => void | Promise<void>) | undefined}
        */
-      async step(nameOrTestDefinition, fn) {
+      async step(nameOrFnOrOptions, maybeFn) {
         if (MapPrototypeGet(testStates, desc.id).finalized) {
           throw new Error(
             "Cannot run test step after parent scope has finished execution. " +
@@ -1277,16 +1277,29 @@
         }
 
         let stepDesc;
-        if (typeof nameOrTestDefinition === "string") {
-          if (!(ObjectPrototypeIsPrototypeOf(FunctionPrototype, fn))) {
+        if (typeof nameOrFnOrOptions === "string") {
+          if (!(ObjectPrototypeIsPrototypeOf(FunctionPrototype, maybeFn))) {
             throw new TypeError("Expected function for second argument.");
           }
           stepDesc = {
-            name: nameOrTestDefinition,
-            fn,
+            name: nameOrFnOrOptions,
+            fn: maybeFn,
           };
-        } else if (typeof nameOrTestDefinition === "object") {
-          stepDesc = nameOrTestDefinition;
+        } else if (typeof nameOrFnOrOptions === "function") {
+          if (!nameOrFnOrOptions.name) {
+            throw new TypeError("The step function must have a name.");
+          }
+          if (maybeFn != undefined) {
+            throw new TypeError(
+              "Unexpected second argument to TestContext.step()",
+            );
+          }
+          stepDesc = {
+            name: nameOrFnOrOptions.name,
+            fn: nameOrFnOrOptions,
+          };
+        } else if (typeof nameOrFnOrOptions === "object") {
+          stepDesc = nameOrFnOrOptions;
         } else {
           throw new TypeError(
             "Expected a test definition or name and function.",

cli/tests/testdata/test/steps/passing_steps.out

@@ -1,11 +1,17 @@
 [WILDCARD]
-running 5 tests from ./test/steps/passing_steps.ts
+running 6 tests from ./test/steps/passing_steps.ts
 description ...
   step 1 ...
     inner 1 ... ok ([WILDCARD]ms)
     inner 2 ... ok ([WILDCARD]ms)
   step 1 ... ok ([WILDCARD]ms)
 description ... ok ([WILDCARD]ms)
+description function as first arg ...
+  step1 ...
+    inner1 ... ok ([WILDCARD]ms)
+    inner1 ... ok ([WILDCARD]ms)
+  step1 ... ok ([WILDCARD]ms)
+description function as first arg ... ok ([WILDCARD]ms)
 parallel steps without sanitizers ...
   step 1 ... ok ([WILDCARD])
   step 2 ... ok ([WILDCARD])
@@ -35,4 +41,4 @@ steps buffered then streaming reporting ...
   step 2 ... ok ([WILDCARD])
 steps buffered then streaming reporting ... ok ([WILDCARD])
 
-ok | 5 passed (18 steps) | 0 failed [WILDCARD]
+ok | 6 passed (21 steps) | 0 failed [WILDCARD]

cli/tests/testdata/test/steps/passing_steps.ts

@@ -9,6 +9,15 @@ Deno.test("description", async (t) => {
   if (!success) throw new Error("Expected the step to return true.");
 });
 
+Deno.test("description function as first arg", async (t) => {
+  const success = await t.step(async function step1(t) {
+    await t.step(function inner1() {});
+    await t.step(function inner1() {});
+  });
+
+  if (!success) throw new Error("Expected the step to return true.");
+});
+
 Deno.test("parallel steps without sanitizers", async (t) => {
   // allowed
   await Promise.all([

cli/tests/unit/testing_test.ts

@@ -114,7 +114,7 @@ Deno.test(async function invalidStepArguments(t) {
       await (t as any).step(() => {});
     },
     TypeError,
-    "Expected a test definition or name and function.",
+    "The step function must have a name.",
   );
 });
 

cli/tsc/dts/lib.deno.ns.d.ts

@@ -668,6 +668,25 @@ declare namespace Deno {
       name: string,
       fn: (t: TestContext) => void | Promise<void>,
     ): Promise<boolean>;
+
+    /** Run a sub step of the parent test or step. Returns a promise
+     * that resolves to a boolean signifying if the step completed successfully.
+     *
+     * The returned promise never rejects unless the arguments are invalid.
+     *
+     * If the test was ignored the promise returns `false`.
+     *
+     * ```ts
+     * Deno.test(async function aParentTest(t) {
+     *   console.log("before the step");
+     *   await t.step(function step1(t) {
+     *     console.log("current step:", t.name);
+     *   });
+     *   console.log("after the step");
+     * });
+     * ```
+     */
+    step(fn: (t: TestContext) => void | Promise<void>): Promise<boolean>;
   }
 
   /** @category Testing */