From 36009e3ca78cb92914e72a59633ea219d601fc4f Mon Sep 17 00:00:00 2001
From: Max Semenik <maxsem.wiki@gmail.com>
Date: Tue, 28 Nov 2017 18:51:25 -0800
Subject: [PATCH] Shell: skip null parameters

Right now they're treated as empty strings, however
this doesn't allow skipping parameters in the middle like
 $params = [
     'foo',
     $x ? '--bar' : null,
     '--baz',
 ];

In some cases this matters, e.g. `ls` works while `ls ''` doesn't.

Also, fix spacing problems the new tests uncovered:
* Extra space when using params()
* Missing space when combining params() and unsafeParams()

Change-Id: Icb29d4c48ae7f92fb5635e3865346c98f47abb01
---
 includes/shell/Command.php                   | 11 +++++++++--
 includes/shell/Shell.php                     |  5 ++++-
 tests/phpunit/includes/shell/CommandTest.php | 11 +++++++++++
 tests/phpunit/includes/shell/ShellTest.php   |  1 +
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/includes/shell/Command.php b/includes/shell/Command.php
index 264c3b48cc..998b3ed905 100644
--- a/includes/shell/Command.php
+++ b/includes/shell/Command.php
@@ -106,6 +106,7 @@ class Command {
 
 	/**
 	 * Adds parameters to the command. All parameters are sanitized via Shell::escape().
+	 * Null values are ignored.
 	 *
 	 * @param string|string[] $args,...
 	 * @return $this
@@ -117,13 +118,14 @@ class Command {
 			// treat it as a list of arguments
 			$args = reset( $args );
 		}
-		$this->command .= ' ' . Shell::escape( $args );
+		$this->command = trim( $this->command . ' ' . Shell::escape( $args ) );
 
 		return $this;
 	}
 
 	/**
 	 * Adds unsafe parameters to the command. These parameters are NOT sanitized in any way.
+	 * Null values are ignored.
 	 *
 	 * @param string|string[] $args,...
 	 * @return $this
@@ -135,7 +137,12 @@ class Command {
 			// treat it as a list of arguments
 			$args = reset( $args );
 		}
-		$this->command .= implode( ' ', $args );
+		$args = array_filter( $args,
+			function ( $value ) {
+				return $value !== null;
+			}
+		);
+		$this->command = trim( $this->command . ' ' . implode( ' ', $args ) );
 
 		return $this;
 	}
diff --git a/includes/shell/Shell.php b/includes/shell/Shell.php
index 6e4fd02a13..084e10e793 100644
--- a/includes/shell/Shell.php
+++ b/includes/shell/Shell.php
@@ -142,7 +142,7 @@ class Shell {
 	 * PHP 5.2.6+ (bug backported to earlier distro releases of PHP).
 	 *
 	 * @param string $args,... strings to escape and glue together, or a single array of
-	 *     strings parameter
+	 *     strings parameter. Null values are ignored.
 	 * @return string
 	 */
 	public static function escape( /* ... */ ) {
@@ -156,6 +156,9 @@ class Shell {
 		$first = true;
 		$retVal = '';
 		foreach ( $args as $arg ) {
+			if ( $arg === null ) {
+				continue;
+			}
 			if ( !$first ) {
 				$retVal .= ' ';
 			} else {
diff --git a/tests/phpunit/includes/shell/CommandTest.php b/tests/phpunit/includes/shell/CommandTest.php
index 81fae33c84..f7275e14e8 100644
--- a/tests/phpunit/includes/shell/CommandTest.php
+++ b/tests/phpunit/includes/shell/CommandTest.php
@@ -1,6 +1,7 @@
 <?php
 
 use MediaWiki\Shell\Command;
+use Wikimedia\TestingAccessWrapper;
 
 /**
  * @group Shell
@@ -103,6 +104,16 @@ class CommandTest extends PHPUnit_Framework_TestCase {
 		$this->assertRegExp( '/^.+no-such-file.*$/m', $result->getStderr() );
 	}
 
+	/**
+	 * Test that null values are skipped by params() and unsafeParams()
+	 */
+	public function testNullsAreSkipped() {
+		$command = TestingAccessWrapper::newFromObject( new Command );
+		$command->params( 'echo', 'a', null, 'b' );
+		$command->unsafeParams( 'c', null, 'd' );
+		$this->assertEquals( "'echo' 'a' 'b' c d", $command->command );
+	}
+
 	public function testT69870() {
 		$commandLine = wfIsWindows()
 			// 333 = 331 + CRLF
diff --git a/tests/phpunit/includes/shell/ShellTest.php b/tests/phpunit/includes/shell/ShellTest.php
index 1e91074fd4..7c96c3c856 100644
--- a/tests/phpunit/includes/shell/ShellTest.php
+++ b/tests/phpunit/includes/shell/ShellTest.php
@@ -25,6 +25,7 @@ class ShellTest extends PHPUnit_Framework_TestCase {
 			'simple' => [ [ 'true' ], "'true'" ],
 			'with args' => [ [ 'convert', '-font', 'font name' ], "'convert' '-font' 'font name'" ],
 			'array' => [ [ [ 'convert', '-font', 'font name' ] ], "'convert' '-font' 'font name'" ],
+			'skip nulls' => [ [ 'ls', null ], "'ls'" ],
 		];
 	}
 }
-- 
2.20.1