Add `util.inspect.custom` support to `util.inspect/Bun.inspect/console.log` (#4194)

* start work on util.inspect.custom

* asdf

* finish util inspect custom inspect

* inspect

* fix tests

* revert

* tidy

* revert

* oops

* test

* fix issues

1 files changed, 155 insertions, 0 deletions

diff --git a/test/js/node/util/custom-inspect.test.js b/test/js/node/util/custom-inspect.test.js
new file mode 100644
index 000000000..06cad262a
--- /dev/null
+++ b/test/js/node/util/custom-inspect.test.js
@@ -0,0 +1,155 @@
+// this file is compatible with jest to test node.js' util.inspect as well as bun's
+
+const util = require("util");
+
+test("util.inspect.custom exists", () => {
+  expect(util.inspect.custom).toEqual(Symbol.for("nodejs.util.inspect.custom"));
+});
+
+const customSymbol = util.inspect.custom;
+
+for (const [name, inspect] of process.versions.bun
+  ? [
+      ["util.inspect", util.inspect],
+      ["Bun.inspect", Bun.inspect],
+    ]
+  : [["util.inspect", util.inspect]]) {
+  test(name + " calls inspect.custom", () => {
+    const obj = {
+      [customSymbol]() {
+        return "42";
+      },
+    };
+
+    expect(inspect(obj)).toBe("42");
+  });
+
+  test(name + " calls inspect.custom recursivly", () => {
+    const obj = {
+      [customSymbol]() {
+        return {
+          [customSymbol]() {
+            return "42";
+          },
+        };
+      },
+    };
+
+    expect(inspect(obj)).toBe("42");
+  });
+
+  test(name + " calls inspect.custom recursivly nested", () => {
+    const obj = {
+      [customSymbol]() {
+        return {
+          prop: {
+            [customSymbol]() {
+              return "42";
+            },
+          },
+        };
+      },
+    };
+
+    expect(inspect(obj).replace(/\s/g, "")).toBe("{prop:42}");
+  });
+
+  test(name + " calls inspect.custom recursivly nested 2", () => {
+    const obj = {
+      prop: {
+        [customSymbol]() {
+          return {
+            [customSymbol]() {
+              return "42";
+            },
+          };
+        },
+      },
+    };
+
+    expect(inspect(obj).replace(/\s/g, "")).toBe("{prop:42}");
+  });
+
+  test(name + " calls inspect.custom with valid options", () => {
+    const obj = {
+      [customSymbol](depth, options, inspect) {
+        expect(this === obj).toBe(true);
+        expect(inspect).toBe(util.inspect);
+        expect(options.stylize).toBeDefined();
+        expect(depth).toBeDefined(2);
+        return "good";
+      },
+    };
+
+    expect(inspect(obj).replace(/\s/g, "")).toBe("good");
+  });
+
+  test(name + " stylize function works without color", () => {
+    const obj = {
+      [customSymbol](depth, options, inspect) {
+        expect(options.stylize).toBeDefined();
+        expect(options.stylize("foo", "whatever")).toBe("foo");
+        expect(options.stylize("hello", "string")).toBe("hello");
+        return "good";
+      },
+    };
+
+    expect(inspect(obj).replace(/\s/g, "")).toBe("good");
+  });
+
+  test(name + " stylize function works with color", () => {
+    const obj = {
+      [customSymbol](depth, options, inspect) {
+        expect(options.stylize).toBeDefined();
+        expect(options.stylize("foo", "invalid")).toBe("foo");
+        expect(options.stylize("foo", "boolean")).toBe("\u001b[33mfoo\u001b[39m");
+        expect(options.stylize("hello", "string")).toBe("\u001b[32mhello\u001b[39m");
+        return "good";
+      },
+    };
+
+    expect(inspect(obj, { colors: true }).replace(/\s/g, "")).toBe("good");
+  });
+
+  test(name + " stylize function gives correct depth", () => {
+    const obj = {
+      [customSymbol](depth, options, inspect) {
+        return [depth, options.depth];
+      },
+    };
+    expect(inspect(obj, { depth: 3 }).replace(/\s/g, "")).toBe("[3,3]");
+  });
+  test(name + " stylize function gives correct depth", () => {
+    const obj = {
+      prop: {
+        [customSymbol](depth, options, inspect) {
+          return [depth, options.depth];
+        },
+      },
+    };
+    expect(inspect(obj, { depth: 3 }).replace(/\s/g, "")).toBe("{prop:[2,3]}");
+  });
+  test(name + " non-callable does not get called", () => {
+    const obj = {
+      [customSymbol]: 512,
+    };
+    expect(inspect(obj, { depth: 3 }).replace(/\s/g, "")).toBe("{[Symbol(nodejs.util.inspect.custom)]:512}");
+  });
+
+  const exceptions = [new Error("don't crash!"), 42];
+
+  test.each(exceptions)(name + " handles exceptions %s", err => {
+    const obj = {
+      [customSymbol]() {
+        throw err;
+      },
+    };
+
+    if (Bun.inspect === inspect) {
+      // make sure this doesnt crash
+      expect(inspect(obj)).toBeString();
+    } else {
+      expect(() => inspect(obj)).toThrow();
+    }
+  });
+}