Romaji to Kana Converter: Angular & Express — Chapter 7, Exercise 1
=====================================================================

TASK
Run ng generate environments in a fresh copy of the project (or a
scratch project if you don't want to touch the real one yet), and
inspect the real generated files and angular.json changes. Confirm
environment.ts and environment.development.ts exist with the shape
this chapter describes, and confirm the fileReplacements block was
added automatically under the development configuration.

SOLUTION

  $ ng generate environments
  CREATE src/environments/environment.ts (31 bytes)
  CREATE src/environments/environment.development.ts (31 bytes)
  UPDATE angular.json (...)

Inspecting the two generated files -- both start out identical,
before this chapter's own edits:

  // src/environments/environment.ts
  export const environment = {

  };

  // src/environments/environment.development.ts
  export const environment = {

  };

Inspecting angular.json's own "development" build configuration
confirms the real, automatically-added block:

  "configurations": {
    "development": {
      "fileReplacements": [
        {
          "replace": "src/environments/environment.ts",
          "with": "src/environments/environment.development.ts"
        }
      ],
      ...
    },
    "production": {
      ...
      // no fileReplacements entry here at all -- production uses
      // environment.ts directly, unreplaced
    }
  }

After that, editing the two files by hand to add apiBaseUrl (empty in
environment.ts, 'http://localhost:4000' in environment.development.ts)
is exactly the chapter's own two code blocks.

WHY THIS WORKS AS AN ANSWER
----------------------------
It confirms directly, rather than assuming from the chapter's own
prose, that current Angular genuinely does not create any environment
files on its own -- there is nothing under src/environments/ at all
until ng generate environments is run explicitly -- and that the real
fileReplacements wiring only exists under the "development"
configuration, never "production," which is exactly why a plain
ng build with no configuration flag ends up bundling environment.ts
completely unmodified.