Improve error message for an invalid sniff code

src/Config.php

@@ -885,32 +885,14 @@ public function processLongArgument($arg, $pos)
                     break;
                 }
 
-                $sniffs = explode(',', substr($arg, 7));
-                foreach ($sniffs as $sniff) {
-                    if (substr_count($sniff, '.') !== 2) {
-                        $error  = 'ERROR: The specified sniff code "'.$sniff.'" is invalid'.PHP_EOL.PHP_EOL;
-                        $error .= $this->printShortUsage(true);
-                        throw new DeepExitException($error, 3);
-                    }
-                }
-
-                $this->sniffs = $sniffs;
+                $this->sniffs = $this->parseSniffCodes(substr($arg, 7), 'sniffs');
                 self::$overriddenDefaults['sniffs'] = true;
             } else if (substr($arg, 0, 8) === 'exclude=') {
                 if (isset(self::$overriddenDefaults['exclude']) === true) {
                     break;
                 }
 
-                $sniffs = explode(',', substr($arg, 8));
-                foreach ($sniffs as $sniff) {
-                    if (substr_count($sniff, '.') !== 2) {
-                        $error  = 'ERROR: The specified sniff code "'.$sniff.'" is invalid'.PHP_EOL.PHP_EOL;
-                        $error .= $this->printShortUsage(true);
-                        throw new DeepExitException($error, 3);
-                    }
-                }
-
-                $this->exclude = $sniffs;
+                $this->exclude = $this->parseSniffCodes(substr($arg, 8), 'exclude');
                 self::$overriddenDefaults['exclude'] = true;
             } else if (defined('PHP_CODESNIFFER_IN_TESTS') === false
                 && substr($arg, 0, 6) === 'cache='
@@ -1277,6 +1259,93 @@ public function processLongArgument($arg, $pos)
     }//end processLongArgument()
 
 
+    /**
+     * Parse supplied string into a list of validated sniff codes.
+     *
+     * @param string $input    Comma-separated string of sniff codes.
+     * @param string $argument The name of the argument which is being processed.
+     *
+     * @return array<string>
+     * @throws DeepExitException When any of the provided codes are not valid as sniff codes.
+     */
+    private function parseSniffCodes($input, $argument)
+    {
+        $errors = [];
+        $sniffs = [];
+
+        $possibleSniffs = array_filter(explode(',', $input));
+
+        if ($possibleSniffs === []) {
+            $errors[] = 'No codes specified / empty argument';
+        }
+
+        foreach ($possibleSniffs as $sniff) {
+            $sniff = trim($sniff);
+
+            $partCount = substr_count($sniff, '.');
+            if ($partCount === 2) {
+                // Correct number of parts.
+                $sniffs[] = $sniff;
+                continue;
+            }
+
+            if ($partCount === 0) {
+                $errors[] = 'Standard codes are not supported: '.$sniff;
+            } else if ($partCount === 1) {
+                $errors[] = 'Category codes are not supported: '.$sniff;
+            } else if ($partCount === 3) {
+                $errors[] = 'Message codes are not supported: '.$sniff;
+            } else {
+                $errors[] = 'Too many parts: '.$sniff;
+            }
+
+            if ($partCount > 2) {
+                $parts    = explode('.', $sniff, 4);
+                $sniffs[] = $parts[0].'.'.$parts[1].'.'.$parts[2];
+            }
+        }//end foreach
+
+        $sniffs = array_reduce(
+            $sniffs,
+            static function ($carry, $item) {
+                $lower = strtolower($item);
+
+                foreach ($carry as $found) {
+                    if ($lower === strtolower($found)) {
+                        // This sniff is already in our list.
+                        return $carry;
+                    }
+                }
+
+                $carry[] = $item;
+
+                return $carry;
+            },
+            []
+        );
+
+        if ($errors !== []) {
+            $error  = 'ERROR: The --'.$argument.' option only supports sniff codes.'.PHP_EOL;
+            $error .= 'Sniff codes are in the form "Standard.Category.Sniff".'.PHP_EOL;
+            $error .= PHP_EOL;
+            $error .= 'The following problems were detected:'.PHP_EOL;
+            $error .= '* '.implode(PHP_EOL.'* ', $errors).PHP_EOL;
+
+            if ($sniffs !== []) {
+                $error .= PHP_EOL;
+                $error .= 'Perhaps try --'.$argument.'="'.implode(',', $sniffs).'" instead.'.PHP_EOL;
+            }
+
+            $error .= PHP_EOL;
+            $error .= $this->printShortUsage(true);
+            throw new DeepExitException(ltrim($error), 3);
+        }
+
+        return $sniffs;
+
+    }//end parseSniffCodes()
+
+
     /**
      * Processes an unknown command line argument.
      *