fix: env handling and inheritance

src/Command.php

@@ -10,15 +10,14 @@ use ValueError;
 /**
  * A process builder, providing fine-grained control over how a new process
  * should be spawned.
- *
- * TODO: Wonky env handling.
  */
 final class Command implements Stringable
 {
     public readonly string $program;
 
     private array $args;
-    private ?array $envs = null;
+    private ?array $environment = null;
+    private bool $environmentInherit = true;
     private ?string $cwd = null;
 
     private ?Stdio $stdin = null;
@@ -26,7 +25,17 @@ final class Command implements Stringable
     private ?Stdio $stderr = null;
 
     /**
+     * Constructs a new Command for launching the program at path program, with
+     * the following default configuration:
      *
+     * - No arguments to the program
+     * - Inherit the current process's environment
+     * - Inherit the current process's working directory
+     * - Inherit stdin/stdout/stderr for spawn or status, but create pipes for
+     *   output
+     *
+     * Builder methods are provided to change these defaults and otherwise
+     * configure the process.
      */
     public function __construct(string $program)
     {
@@ -40,6 +49,22 @@ final class Command implements Stringable
 
     /**
      * Adds an argument to pass to the program.
+     *
+     * Only one argument can be passed per use. So instead of:
+     *
+     * ```
+     * $command->arg('-C /path/to/repo');
+     * ```
+     *
+     * usage would be:
+     *
+     * ```
+     * $command
+     *     ->arg('-C')
+     *     ->arg('/path/to/repo');
+     * ```
+     *
+     * To pass multiple arguments see {@see Command::args()}.
      */
     public function arg(string|Stringable $arg): static
     {
@@ -50,6 +75,8 @@ final class Command implements Stringable
     /**
      * Adds multiple arguments to pass to the program.
      *
+     * To pass a single argument see {@see Command::arg()}.
+     *
      * @param iterable<string|Stringable> $args
      */
     public function args(iterable $args): static
@@ -63,22 +90,45 @@ final class Command implements Stringable
 
     /**
      * Inserts or updates an explicit environment variable mapping.
+     *
+     * This method allows you to add an environment variable mapping to the
+     * spawned process or overwrite a previously set value. You can use
+     * {@see Command::envs()} to set multiple environment variables
+     * simultaneously.
+     *
+     * Child processes will inherit environment variables from their parent
+     * process by default. Environment variables explicitly set using
+     * {@see Command::env()} take precedence over inherited variables. You can
+     * disable environment variable inheritance entirely using
+     * {@see Command::envClear()} or for a single key using
+     * {@see Command::envRemove()}.
      */
     public function env(string $key, string|Stringable $val): static
     {
-        $this->envs[$key] = $val;
+        $this->environment[$key] = $val;
         return $this;
     }
 
     /**
      * Inserts or updates multiple environment variable mappings.
      *
+     * This method allows you to add multiple environment variable mappings to
+     * the spawned process or overwrite previously set values. You can use
+     * {@see Command::env()} to set a single environment variable.
+     *
+     * Child processes will inherit environment variables from their parent
+     * process by default. Environment variables explicitly set using
+     * {@see Command::envs()} take precedence over inherited variables. You can
+     * disable environment variable inheritance entirely using
+     * {@see Command::envClear()} or for a single key using
+     * {@see Command::envRemove()}.
+     *
      * @param iterable<string, string|Stringable> $vars
      */
     public function envs(iterable $vars): static
     {
         foreach ($vars as $key => $val) {
-            $this->envs[$key] = (string) $val;
+            $this->environment[$key] = (string) $val;
         }
 
         return $this;
@@ -87,27 +137,42 @@ final class Command implements Stringable
     /**
      * Removes an explicitly set environment variable and prevents inheriting it
      * from a parent process.
+     *
+     * This method will remove the explicit value of an environment variable set
+     * via {@see Command::env()} or {@see Command::envs()}. In addition, it will
+     * prevent the spawned child process from inheriting that environment
+     * variable from its parent process.
+     *
+     * After calling {@see Command::envRemove()}, the value associated with its
+     * key from {@see Command::getEnvs()} will be `NULL`.
+     *
+     * To clear all explicitly set environment variables and disable all
+     * environment variable inheritance, you can use {@see Command::envClear()}.
      */
     public function envRemove(string $key): static
     {
-        if (is_null($this->envs)) {
+        $this->environment[$key] = null;
-            $this->envs = getenv();
-        }
-
-        if (isset($this->envs[$key])) {
-            unset($this->envs[$key]);
-        }
-
         return $this;
     }
 
     /**
      * Clears all explicitly set environment variables and prevents inheriting
      * any parent process environment variables.
+     *
+     * This method will remove all explicitly added environment variables set
+     * via {@see Command::env()} or {@see Command::envs()}. In addition, it will
+     * prevent the spawned child process from inheriting any environment
+     * variable from its parent process.
+     *
+     * After calling {@see Command::envClear()}, the array from
+     * {@see Command::getEnvs()} will be empty.
+     *
+     * You can use {@see Command::envRemove()} to clear a single mapping.
      */
     public function envClear(): static
     {
-        $this->envs = [];
+        $this->environmentInherit = false;
+        $this->environment = [];
         return $this;
     }
 
@@ -266,10 +331,17 @@ final class Command implements Stringable
 
     /**
      * Returns the environment variables set for the child process.
+     *
+     * Environment variables explicitly set using {@see Command::env(),
+     * {@see Command::envs()}, and {@see Command::envRemove} can be retrieved
+     * with this method.
+     *
+     * Note that this output does not include environment variables inherited
+     * from the parent process.
      */
     public function getEnvs(): array
     {
-        return $this->envs;
+        return $this->environment ?? [];
     }
 
     /**
@@ -310,7 +382,16 @@ final class Command implements Stringable
             ));
         }
 
-        $proc = proc_open($command, $descriptorSpec, $pipes, $this->cwd, $this->envs);
+        $environment = $this->environment;
+        if (is_array($environment) && $this->environmentInherit) {
+            foreach (getenv() as $key => $val) {
+                if (!array_key_exists($key, $environment)) {
+                    $environment[$key] = $val;
+                }
+            }
+        }
+
+        $proc = proc_open($command, $descriptorSpec, $pipes, $this->cwd, $environment);
         if ($proc === false) {
             throw new CommandException(sprintf(
                 'Program "%s" failed to start',