refactor(@angular/cli): centralize environment variable parsing

packages/angular/cli/src/utilities/environment-options.ts

@@ -6,28 +6,63 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-function isPresent(variable: string | undefined): variable is string {
-  return typeof variable === 'string' && variable !== '';
-}
+/** A set of strings that are considered "truthy" when parsing environment variables. */
+const TRUTHY_VALUES = new Set(['1', 'true']);
 
-function isDisabled(variable: string | undefined): boolean {
-  return isPresent(variable) && (variable === '0' || variable.toLowerCase() === 'false');
-}
+/** A set of strings that are considered "falsy" when parsing environment variables. */
+const FALSY_VALUES = new Set(['0', 'false']);
 
-function isEnabled(variable: string | undefined): boolean {
-  return isPresent(variable) && (variable === '1' || variable.toLowerCase() === 'true');
+/**
+ * Checks if an environment variable is present and has a non-empty value.
+ * @param variable The environment variable to check.
+ * @returns `true` if the variable is a non-empty string.
+ */
+function isPresent(variable: string | undefined): variable is string {
+  return typeof variable === 'string' && variable !== '';
 }
 
-function optional(variable: string | undefined): boolean | undefined {
+/**
+ * Parses an environment variable into a boolean or undefined.
+ * @returns `true` if the variable is truthy ('1', 'true').
+ * @returns `false` if the variable is falsy ('0', 'false').
+ * @returns `undefined` if the variable is not present or has an unknown value.
+ */
+function parseTristate(variable: string | undefined): boolean | undefined {
   if (!isPresent(variable)) {
     return undefined;
   }
 
-  return isEnabled(variable);
+  const value = variable.toLowerCase();
+  if (TRUTHY_VALUES.has(value)) {
+    return true;
+  }
+  if (FALSY_VALUES.has(value)) {
+    return false;
+  }
+
+  return undefined;
 }
 
-export const analyticsDisabled = isDisabled(process.env['NG_CLI_ANALYTICS']);
-export const isCI = isEnabled(process.env['CI']);
-export const disableVersionCheck = isEnabled(process.env['NG_DISABLE_VERSION_CHECK']);
-export const ngDebug = isEnabled(process.env['NG_DEBUG']);
-export const forceAutocomplete = optional(process.env['NG_FORCE_AUTOCOMPLETE']);
+/** Disables all analytics reporting when the `NG_CLI_ANALYTICS` environment variable is set to '0' or 'false'. */
+export const analyticsDisabled = parseTristate(process.env['NG_CLI_ANALYTICS']) === false;
+
+/** Identifies when the CLI is running in a Continuous Integration environment. */
+export const isCI = parseTristate(process.env['CI']) === true;
+
+/** Disables the automatic version check when the `NG_DISABLE_VERSION_CHECK` environment variable is enabled. */
+export const disableVersionCheck = parseTristate(process.env['NG_DISABLE_VERSION_CHECK']) === true;
+
+/** Enables debugging messages when the `NG_DEBUG` environment variable is enabled. */
+export const ngDebug = parseTristate(process.env['NG_DEBUG']) === true;
+
+/**
+ * Forces the autocomplete script to be generated.
+ * The `NG_FORCE_AUTOCOMPLETE` environment variable can be 'true', 'false', or undefined (for default behavior).
+ */
+export const forceAutocomplete = parseTristate(process.env['NG_FORCE_AUTOCOMPLETE']);
+
+/**
+ * When enabled, forces TTY mode.
+ * The `NG_FORCE_TTY` environment variable can be 'true', 'false', or undefined (for default behavior).
+ */
+export const forceTty = parseTristate(process.env['NG_FORCE_TTY']);

packages/angular/cli/src/utilities/tty.ts

@@ -6,17 +6,16 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-function _isTruthy(value: undefined | string): boolean {
-  // Returns true if value is a string that is anything but 0 or false.
-  return value !== undefined && value !== '0' && value.toUpperCase() !== 'FALSE';
-}
+import { forceTty, isCI } from './environment-options';
 
+/**
+ * Determines if the `stream` is a TTY.
+ *
+ * @param stream A NodeJS stream to check. Defaults to `process.stdout`.
+ * @returns `true` if the `stream` is a TTY, `false` otherwise. This detection is overridden
+ * by the `NG_FORCE_TTY` environment variable. In a CI environment, this will also be `false`
+ * unless `NG_FORCE_TTY` is set.
+ */
 export function isTTY(stream: NodeJS.WriteStream = process.stdout): boolean {
-  // If we force TTY, we always return true.
-  const force = process.env['NG_FORCE_TTY'];
-  if (force !== undefined) {
-    return _isTruthy(force);
-  }
-
-  return !!stream.isTTY && !_isTruthy(process.env['CI']);
+  return forceTty ?? (!!stream.isTTY && !isCI);
 }