Handle existing composer.json better

Change the "conflicting files check" from an error to a warning, and
include a bit more information about what is actually going on.

Closes #61.

lib/admin-page.php

@@ -503,38 +503,28 @@ function classicpress_check_can_migrate() {
 	echo "\n</p>\n";
 	echo "</td></tr>\n";
 
-	// Check: Conflicting files
-	$conflicting_files = classicpress_check_conflicting_files();
-	if ( count( $conflicting_files ) > 0 ) {
-		$preflight_checks['conflicting_files'] = false;
-		echo "<tr>\n<td>$icon_preflight_fail</td>\n<td>\n";
-	} else {
-		$preflight_checks['conflicting_files'] = true;
-		echo "<tr>\n<td>$icon_preflight_pass</td>\n<td>\n";
-	}
-	echo "<p>\n";
-	if ( $preflight_checks['conflicting_files'] ) {
+	// Check: Existing `composer.json` file
+	$composer_json_exists = file_exists( ABSPATH . 'composer.json' );
+	if ( $composer_json_exists ) {
+		echo "<tr>\n<td>$icon_preflight_warn</td>\n<td>\n";
+		echo "<p>\n";
 		_e(
-			'No conflicting files were found.',
+			'An existing <code>composer.json</code> file was detected on your site. This file will be <strong class="cp-emphasis">overwritten</strong> during migration.',
 			'switch-to-classicpress'
 		);
-	} else {
+		echo "<br>\n";
 		_e(
-			'Conflicting files detected. These are files that would be <strong class="cp-emphasis">unexpectedly overwritten</strong> during migration.',
+			'If you have previously installed ClassicPress on this site, then you can ignore this warning.',
 			'switch-to-classicpress'
 		);
 		echo "<br>\n";
 		_e(
-			'If you have JavaScript enabled, you can see a list of conflicting files <strong>in your browser console</strong>.',
+			'If you are using <code>composer.json</code> to manage dependencies for this site, then you should <strong class="cp-emphasis">back up this file</strong> before continuing, and restore it after the migration.',
 			'switch-to-classicpress'
 		);
-		echo "\n<script>console.log(";
-		echo "\n'conflicting files, remove them and refresh in order to proceed:',\n";
-		echo wp_json_encode( $conflicting_files );
-		echo "\n);</script>";
+		echo "\n</p>\n";
+		echo "</td></tr>\n";
 	}
-	echo "\n</p>\n";
-	echo "</td></tr>\n";
 
 	// Check: Core files checksums
 	$modified_files = classicpress_check_core_files();
@@ -611,8 +601,7 @@ function classicpress_check_can_migrate() {
 	if (
 		$preflight_checks['wp_version'] &&
 		$preflight_checks['php_version'] &&
-		$preflight_checks['wp_http_supports_ssl'] &&
-		$preflight_checks['conflicting_files']
+		$preflight_checks['wp_http_supports_ssl']
 	) {
 		update_option( 'classicpress_preflight_checks', $preflight_checks, false );
 		return true;

lib/check-core-files.php

@@ -42,24 +42,3 @@ function classicpress_check_core_files( $locale = 'en_US' ) {
 	}
 	return $modified;
 }
-
-/**
- * Check for known conflicting files.
- *
- * @since 1.0.0
- *
- * @return array An array of conflicting filenames (empty if no conflits).
- */
-function classicpress_check_conflicting_files() {
-	$files = array(
-		'composer.json',
-	);
-
-	$conflict = array();
-	foreach ( $files as $file ) {
-		if ( file_exists( ABSPATH . $file ) ) {
-			$conflict[] = $file;
-		}
-	}
-	return $conflict;
-}

lib/update.php

@@ -241,8 +241,7 @@ function classicpress_override_upgrade_page() {
 		! is_array( $preflight_checks ) ||
 		empty( $preflight_checks['wp_version'] ) ||
 		empty( $preflight_checks['php_version'] ) ||
-		empty( $preflight_checks['wp_http_supports_ssl'] ) ||
-		empty( $preflight_checks['conflicting_files'] )
+		empty( $preflight_checks['wp_http_supports_ssl'] )
 	) {
 		return;
 	}