BREAKING(console): remove Deno.customInspect (#25348)

Note: this is implemented on Deploy. However, according to @magurotuna,
a thin compatibility layer might be in the works that'd prevent
breakages for PRs such as this one.

Towards #22079

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

@@ -5216,19 +5216,6 @@ declare namespace Deno {
    */
   export const args: string[];
 
-  /**
-   * A symbol which can be used as a key for a custom method which will be
-   * called when `Deno.inspect()` is called, or when the object is logged to
-   * the console.
-   *
-   * @deprecated This will be removed in Deno 2.0. See the
-   * {@link https://docs.deno.com/runtime/manual/advanced/migrate_deprecations | Deno 1.x to 2.x Migration Guide}
-   * for migration instructions.
-   *
-   * @category I/O
-   */
-  export const customInspect: unique symbol;
-
   /** The URL of the entrypoint module entered from the command-line. It
    * requires read permission to the CWD.
    *

runtime/js/99_main.js

@@ -56,7 +56,6 @@ import * as version from "ext:runtime/01_version.ts";
 import * as os from "ext:runtime/30_os.js";
 import * as timers from "ext:deno_web/02_timers.js";
 import {
-  customInspect,
   getDefaultInspectOptions,
   getStderrNoColor,
   inspectArgs,
@@ -534,18 +533,6 @@ ObjectDefineProperties(finalDenoNs, {
   noColor: core.propGetterOnly(() => op_bootstrap_no_color()),
   args: core.propGetterOnly(opArgs),
   mainModule: core.propGetterOnly(() => op_main_module()),
-  // TODO(kt3k): Remove this export at v2
-  // See https://github.com/denoland/deno/issues/9294
-  customInspect: {
-    get() {
-      warnOnDeprecatedApi(
-        "Deno.customInspect",
-        new Error().stack,
-        'Use `Symbol.for("Deno.customInspect")` instead.',
-      );
-      return internals.future ? undefined : customInspect;
-    },
-  },
   exitCode: {
     get() {
       return os.getExitCode();

tests/specs/future/runtime_api/main.js

@@ -118,6 +118,5 @@ try {
     console.log("Deno.ListenTlsOptions.(keyFile|certFile) do nothing");
   }
 }
-console.log("Deno.customInspect is", Deno.customInspect);
 
 self.close();

tests/specs/future/runtime_api/main.out

@@ -29,4 +29,3 @@ Deno.FsFile constructor is illegal
 Deno.ConnectTlsOptions.(certFile|keyFile) do nothing
 Deno.ConnectTlsOptions.(certChain|privateKey) do nothing
 Deno.ListenTlsOptions.(keyFile|certFile) do nothing
-Deno.customInspect is undefined