diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
index defdbb03..d4f29121 100644
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -612,6 +612,7 @@ phutil_register_library_map(array(
     'PhutilArgumentUsageException' => 'parser/argument/exception/PhutilArgumentUsageException.php',
     'PhutilArgumentWorkflow' => 'parser/argument/workflow/PhutilArgumentWorkflow.php',
     'PhutilArray' => 'utils/PhutilArray.php',
+    'PhutilArrayCheck' => 'utils/PhutilArrayCheck.php',
     'PhutilArrayTestCase' => 'utils/__tests__/PhutilArrayTestCase.php',
     'PhutilArrayWithDefaultValue' => 'utils/PhutilArrayWithDefaultValue.php',
     'PhutilAsanaFuture' => 'future/asana/PhutilAsanaFuture.php',
@@ -1619,6 +1620,7 @@ phutil_register_library_map(array(
       'ArrayAccess',
       'Iterator',
     ),
+    'PhutilArrayCheck' => 'Phobject',
     'PhutilArrayTestCase' => 'PhutilTestCase',
     'PhutilArrayWithDefaultValue' => 'PhutilArray',
     'PhutilAsanaFuture' => 'FutureProxy',
diff --git a/src/lint/linter/ArcanistTextLinter.php b/src/lint/linter/ArcanistTextLinter.php
index c7c4af52..b10c5c46 100644
--- a/src/lint/linter/ArcanistTextLinter.php
+++ b/src/lint/linter/ArcanistTextLinter.php
@@ -261,8 +261,7 @@ final class ArcanistTextLinter extends ArcanistLinter {
         self::LINT_TRAILING_WHITESPACE,
         pht(
           'This line contains trailing whitespace. Consider setting '.
-          'up your editor to automatically remove trailing whitespace, '.
-          'you will save time.'),
+          'up your editor to automatically remove trailing whitespace.'),
         $string,
         '');
     }
diff --git a/src/lint/linter/__tests__/ArcanistLinterTestCase.php b/src/lint/linter/__tests__/ArcanistLinterTestCase.php
index a6dc69b5..85144bc2 100644
--- a/src/lint/linter/__tests__/ArcanistLinterTestCase.php
+++ b/src/lint/linter/__tests__/ArcanistLinterTestCase.php
@@ -64,8 +64,6 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
       $contents,
       array(null, null));
 
-    $basename = basename($file);
-
     if ($config) {
       $config = phutil_json_decode($config);
     } else {
@@ -87,6 +85,14 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
     $caught_exception = false;
 
     try {
+      $path_name = idx($config, 'path');
+
+      if ($path_name !== null) {
+        $basename = basename($path_name);
+      } else {
+        $basename = basename($file);
+      }
+
       $tmp = new TempFile($basename);
       Filesystem::writeFile($tmp, $data);
       $full_path = (string)$tmp;
@@ -97,7 +103,6 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
       }
 
       $dir = dirname($full_path);
-      $path = basename($full_path);
 
       $working_copy = ArcanistWorkingCopyIdentity::newFromRootAndConfigFile(
         $dir,
@@ -106,26 +111,25 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
       $configuration_manager = new ArcanistConfigurationManager();
       $configuration_manager->setWorkingCopyIdentity($working_copy);
 
-
       $engine = new ArcanistUnitTestableLintEngine();
       $engine->setWorkingCopy($working_copy);
       $engine->setConfigurationManager($configuration_manager);
 
-      $path_name = idx($config, 'path', $path);
-      $engine->setPaths(array($path_name));
+      $engine->setPaths(array($basename));
 
       $linter->setEngine($engine);
-      $linter->addPath($path_name);
-      $linter->addData($path_name, $data);
+      $linter->addPath($basename);
+      $linter->addData($basename, $data);
 
       foreach (idx($config, 'config', array()) as $key => $value) {
         $linter->setLinterConfigurationValue($key, $value);
       }
 
       $engine->addLinter($linter);
-      $engine->addFileData($path_name, $data);
+      $engine->addFileData($basename, $data);
 
       $results = $engine->run();
+
       $this->assertEqual(
         1,
         count($results),
@@ -187,9 +191,20 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
       $message = new ArcanistLintMessage();
 
       $severity = idx($parts, 0);
-      $line     = idx($parts, 1);
-      $char     = idx($parts, 2);
-      $code     = idx($parts, 3);
+      $line = idx($parts, 1);
+      if ($line === '') {
+        $line = null;
+      }
+
+      $char = idx($parts, 2);
+      if ($char === '') {
+        $char = null;
+      }
+
+      $code = idx($parts, 3);
+      if ($code === '') {
+        $code = null;
+      }
 
       if ($severity !== null) {
         $message->setSeverity($severity);
@@ -256,46 +271,14 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
     }
 
     if ($missing || $surprising) {
-      $expected = pht('EXPECTED MESSAGES');
-      if ($missing) {
-        foreach ($missing as $message) {
-          $expected .= sprintf(
-            "\n  %s: %s %s",
-            pht(
-              '%s at line %d, char %d',
-              $message->getSeverity(),
-              $message->getLine(),
-              $message->getChar()),
-            $message->getCode(),
-            $message->getName());
-        }
-      } else {
-        $expected .= "\n  ".pht('No messages');
-      }
-
-      $actual = pht('UNEXPECTED MESSAGES');
-      if ($surprising) {
-        foreach ($surprising as $message) {
-          $actual .= sprintf(
-            "\n  %s: %s %s",
-            pht(
-              '%s at line %d, char %d',
-              $message->getSeverity(),
-              $message->getLine(),
-              $message->getChar()),
-            $message->getCode(),
-            $message->getName());
-        }
-      } else {
-        $actual .= "\n  ".pht('No messages');
-      }
-
       $this->assertFailure(
         sprintf(
-          "%s\n\n%s\n\n%s",
-          pht("Lint failed for '%s'.", $file),
-          $expected,
-          $actual));
+          "%s\n%s%s",
+          pht(
+            'Lint emitted an unexpected set of messages for file "%s".',
+            $file),
+          $this->renderMessages(pht('MISSING MESSAGES'), $missing),
+          $this->renderMessages(pht('SURPLUS MESSAGES'), $surprising)));
     }
   }
 
@@ -312,15 +295,78 @@ abstract class ArcanistLinterTestCase extends PhutilTestCase {
   /**
    * Compare properties of @{class:ArcanistLintMessage} instances.
    *
-   * The expectation is that if one (or both) of the properties is null, then
-   * we don't care about its value.
-   *
    * @param  wild
    * @param  wild
    * @return bool
    */
   private static function compareLintMessageProperty($x, $y) {
-    return $x === null || $y === null || $x === $y;
+    if ($x === null) {
+      return true;
+    }
+
+    return ($x === $y);
+  }
+
+  private function renderMessages($header, array $messages) {
+    if (!$messages) {
+      $display = tsprintf(
+        "%s\n",
+        pht('(No messages.)'));
+    } else {
+      $lines = array();
+      foreach ($messages as $message) {
+        $line = $message->getLine();
+        if ($line === null) {
+          $display_line = pht('<null>');
+        } else {
+          $display_line = $line;
+        }
+
+        $char = $message->getChar();
+        if ($char === null) {
+          $display_char = pht('<null>');
+        } else {
+          $display_char = $char;
+        }
+
+        $code = $message->getCode();
+        $name = $message->getName();
+        if ($code !== null && $name !== null) {
+          $display_code = pht('%s: %s', $code, $name);
+        } else if ($code !== null) {
+          $display_code = pht('%s', $code);
+        } else {
+          $display_code = null;
+        }
+
+        $severity = $message->getSeverity();
+
+        if ($display_code === null) {
+          $display_message = pht(
+            'Message with severity "%s" at "%s:%s"',
+            $severity,
+            $display_line,
+            $display_char);
+        } else {
+          $display_message = pht(
+            'Message with severity "%s" at "%s:%s" (%s)',
+            $severity,
+            $display_line,
+            $display_char,
+            $display_code);
+        }
+
+        $lines[] = tsprintf(
+          "    %s\n",
+          $display_message);
+      }
+      $display = implode('', $lines);
+    }
+
+    return tsprintf(
+      "%s\n%B\n",
+      $header,
+      $display);
   }
 
 }
diff --git a/src/lint/linter/__tests__/chmod/empty_executable.lint-test b/src/lint/linter/__tests__/chmod/empty_executable.lint-test
index cf8980b6..695d3b8e 100644
--- a/src/lint/linter/__tests__/chmod/empty_executable.lint-test
+++ b/src/lint/linter/__tests__/chmod/empty_executable.lint-test
@@ -1,5 +1,5 @@
 ~~~~~~~~~~
-warning:0:0:CHMOD1:Invalid Executable
+warning:::CHMOD1:Invalid Executable
 ~~~~~~~~~~
 ~~~~~~~~~~
 {"mode": "0755"}
diff --git a/src/lint/linter/__tests__/cpplint/googlestyle.lint-test b/src/lint/linter/__tests__/cpplint/googlestyle.lint-test
index 5417f073..0c5b1b79 100644
--- a/src/lint/linter/__tests__/cpplint/googlestyle.lint-test
+++ b/src/lint/linter/__tests__/cpplint/googlestyle.lint-test
@@ -1,10 +1,21 @@
 #include "library.cpp"
 #include <stdio>
 
+void main()
+{
+}
+~~~~~~~~~
+warning
+warning:2
+warning:5
+~~~~~~~~~~
+#include "library.cpp"
+#include <stdio>
+
 void main()
 {
 }
 ~~~~~~~~~~
-warning:0:
-warning:2:
-warning:5:
+{
+  "path": "example.cpp"
+}
diff --git a/src/lint/linter/__tests__/filename/bad_filename.lint-test b/src/lint/linter/__tests__/filename/bad_filename.lint-test
index 12ec5757..28b7e560 100644
--- a/src/lint/linter/__tests__/filename/bad_filename.lint-test
+++ b/src/lint/linter/__tests__/filename/bad_filename.lint-test
@@ -1,5 +1,5 @@
 ~~~~~~~~~~
-error:0:0:NAME1:Bad Filename
+error:::NAME1:Bad Filename
 ~~~~~~~~~~
 ~~~~~~~~~~
 {"path": "bad@filename"}
diff --git a/src/lint/linter/__tests__/php/fatal.lint-test b/src/lint/linter/__tests__/php/fatal.lint-test
index 6d3c7b82..04bd5c86 100644
--- a/src/lint/linter/__tests__/php/fatal.lint-test
+++ b/src/lint/linter/__tests__/php/fatal.lint-test
@@ -4,4 +4,4 @@ function f() {
   $this = "cannot be re-assigned";
 }
 ~~~~~~~~~
-error:4:0:PHP2:Fatal Error
+error:4::PHP2:Fatal Error
diff --git a/src/lint/linter/__tests__/php/syntax.lint-test b/src/lint/linter/__tests__/php/syntax.lint-test
index 279fb7af..098a9f68 100644
--- a/src/lint/linter/__tests__/php/syntax.lint-test
+++ b/src/lint/linter/__tests__/php/syntax.lint-test
@@ -4,4 +4,4 @@ function f() {
   this is bad syntax;
 }
 ~~~~~~~~~
-error:4:0:PHP1:Parse Error
+error:4::PHP1:Parse Error
diff --git a/src/lint/linter/__tests__/ruby/hello.lint-test b/src/lint/linter/__tests__/ruby/hello.lint-test
index f6693b6c..a9bf9016 100644
--- a/src/lint/linter/__tests__/ruby/hello.lint-test
+++ b/src/lint/linter/__tests__/ruby/hello.lint-test
@@ -1,4 +1,4 @@
 def hello()
   puts "hello world"
 ~~~~~~~~~~
-error:2:0:RUBY:Syntax Error
+error:2::RUBY:Syntax Error
diff --git a/src/lint/linter/__tests__/text/empty.lint-test b/src/lint/linter/__tests__/text/empty.lint-test
index 72fb27ca..d4bf5989 100644
--- a/src/lint/linter/__tests__/text/empty.lint-test
+++ b/src/lint/linter/__tests__/text/empty.lint-test
@@ -1,4 +1,4 @@
 
 
 ~~~~~~~~~~
-error:0:0:TXT10:Empty File
+error:::TXT10:Empty File
diff --git a/src/lint/linter/__tests__/xhpast/empty.lint-test b/src/lint/linter/__tests__/xhpast/empty.lint-test
index 22cca1cd..c0b9b003 100644
--- a/src/lint/linter/__tests__/xhpast/empty.lint-test
+++ b/src/lint/linter/__tests__/xhpast/empty.lint-test
@@ -1,4 +1,4 @@
 <?php
 
 ~~~~~~~~~~
-warning:0:0:XHP82:Empty File
+warning:::XHP82:Empty File
diff --git a/src/utils/PhutilArrayCheck.php b/src/utils/PhutilArrayCheck.php
new file mode 100644
index 00000000..1b8ce131
--- /dev/null
+++ b/src/utils/PhutilArrayCheck.php
@@ -0,0 +1,278 @@
+<?php
+
+final class PhutilArrayCheck
+  extends Phobject {
+
+  private $instancesOf;
+  private $uniqueMethod;
+  private $context;
+
+  private $object;
+  private $method;
+
+  public function setInstancesOf($instances_of) {
+    $this->instancesOf = $instances_of;
+    return $this;
+  }
+
+  public function getInstancesOf() {
+    return $this->instancesOf;
+  }
+
+  public function setUniqueMethod($unique_method) {
+    $this->uniqueMethod = $unique_method;
+    return $this;
+  }
+
+  public function getUniqueMethod() {
+    return $this->uniqueMethod;
+  }
+
+  public function setContext($object, $method) {
+    if (is_array($object)) {
+      foreach ($object as $idx => $value) {
+        if (!is_object($value)) {
+          throw new Exception(
+            pht(
+              'Expected an object, string, or list of objects for "object" '.
+              'context. Got a list ("%s"), but the list item at index '.
+              '"%s" (with type "%s") is not an object.',
+              phutil_describe_type($object),
+              $idx,
+              phutil_describe_type($value)));
+        }
+      }
+    } else if (!is_object($object) && !is_string($object)) {
+      throw new Exception(
+        pht(
+          'Expected an object, string, or list of objects for "object" '.
+          'context, got "%s".',
+          phutil_describe_type($object)));
+    }
+
+    if (!is_string($method)) {
+      throw new Exception(
+        pht(
+          'Expected a string for "method" context, got "%s".',
+          phutil_describe_type($method)));
+    }
+
+    $argv = func_get_args();
+    $argv = array_slice($argv, 2);
+
+    $this->context = array(
+      'object' => $object,
+      'method' => $method,
+      'argv' => $argv,
+    );
+
+    return $this;
+  }
+
+  public function checkValues($maps) {
+    foreach ($maps as $idx => $map) {
+      $maps[$idx] = $this->checkValue($map);
+    }
+
+    $unique = $this->getUniqueMethod();
+    if ($unique === null) {
+      $result = array();
+
+      foreach ($maps as $map) {
+        foreach ($map as $value) {
+          $result[] = $value;
+        }
+      }
+    } else {
+      $items = array();
+      foreach ($maps as $idx => $map) {
+        foreach ($map as $key => $value) {
+          $items[$key][$idx] = $value;
+        }
+      }
+
+      foreach ($items as $key => $values) {
+        if (count($values) === 1) {
+          continue;
+        }
+        $this->raiseValueException(
+          pht(
+            'Unexpected return value from calls to "%s(...)". More than one '.
+            'object returned a value with unique key "%s". This key was '.
+            'returned by objects with indexes: %s.',
+            $unique,
+            $key,
+            implode(', ', array_keys($values))));
+      }
+
+      $result = array();
+      foreach ($items as $key => $values) {
+        $result[$key] = head($values);
+      }
+    }
+
+    return $result;
+  }
+
+  public function checkValue($items) {
+    if (!$this->context) {
+      throw new PhutilInvalidStateException('setContext');
+    }
+
+    if (!is_array($items)) {
+      $this->raiseValueException(
+        pht(
+          'Expected value to be a list, got "%s".',
+          phutil_describe_type($items)));
+    }
+
+    $instances_of = $this->getInstancesOf();
+    if ($instances_of !== null) {
+      foreach ($items as $idx => $item) {
+        if (!($item instanceof $instances_of)) {
+          $this->raiseValueException(
+            pht(
+              'Expected value to be a list of objects which are instances of '.
+              '"%s", but item with index "%s" is "%s".',
+              $instances_of,
+              $idx,
+              phutil_describe_type($item)));
+        }
+      }
+    }
+
+    $unique = $this->getUniqueMethod();
+    if ($unique !== null) {
+      if ($instances_of === null) {
+        foreach ($items as $idx => $item) {
+          if (!is_object($item)) {
+            $this->raiseValueException(
+              pht(
+                'Expected value to be a list of objects to support calling '.
+                '"%s" to generate unique keys, but item with index "%s" is '.
+                '"%s".',
+                $unique,
+                $idx,
+                phutil_describe_type($item)));
+          }
+        }
+      }
+
+      $map = array();
+
+      foreach ($items as $idx => $item) {
+        $key = call_user_func(array($item, $unique));
+
+        if (!is_string($key) && !is_int($key)) {
+          $this->raiseValueException(
+            pht(
+              'Expected method "%s->%s()" to return a string or integer for '.
+              'use as a unique key, got "%s" from object at index "%s".',
+              get_class($item),
+              $unique,
+              phutil_describe_type($key),
+              $idx));
+        }
+
+        $key = phutil_string_cast($key);
+
+        $map[$key][$idx] = $item;
+      }
+
+      $result = array();
+      foreach ($map as $key => $values) {
+        if (count($values) === 1) {
+          $result[$key] = head($values);
+          continue;
+        }
+
+        $classes = array();
+        foreach ($values as $value) {
+          $classes[] = get_class($value);
+        }
+        $classes = array_fuse($classes);
+
+        if (count($classes) === 1) {
+          $class_display = head($classes);
+        } else {
+          $class_display = sprintf(
+            '[%s]',
+            implode(', ', $classes));
+        }
+
+        $index_display = array();
+        foreach ($values as $idx => $value) {
+          $index_display[] = pht(
+            '"%s" (%s)',
+            $idx,
+            get_class($value));
+        }
+        $index_display = implode(', ', $index_display);
+
+        $this->raiseValueException(
+          pht(
+            'Expected method "%s->%s()" to return a unique key, got "%s" '.
+            'from %s object(s) at indexes: %s.',
+            $class_display,
+            $unique,
+            $key,
+            phutil_count($values),
+            $index_display));
+      }
+
+      $items = $result;
+    }
+
+    return $items;
+  }
+
+  private function raiseValueException($message) {
+    $context = $this->context;
+
+    $object = $context['object'];
+    $method = $context['method'];
+    $argv = $context['argv'];
+
+    if (is_array($object)) {
+      $classes = array();
+      foreach ($object as $item) {
+        $classes[] = get_class($item);
+      }
+      $classes = array_fuse($classes);
+      $n = count($object);
+
+      $object_display = sprintf(
+        '[%s]<%d>->%s',
+        implode(', ', $classes),
+        $n,
+        $method);
+    } else if (is_object($object)) {
+      $object_display = sprintf(
+        '%s->%s',
+        get_class($object),
+        $method);
+    } else {
+      $object_display = sprintf(
+        '%s::%s',
+        $object,
+        $method);
+    }
+
+    if (count($argv)) {
+      $call_display = sprintf(
+        '%s(...)',
+        $object_display);
+    } else {
+      $call_display = sprintf(
+        '%s()',
+        $object_display);
+    }
+
+    throw new Exception(
+      pht(
+        'Unexpected return value from call to "%s": %s.',
+        $call_display,
+        $message));
+  }
+
+}
diff --git a/src/workflow/ArcanistLiberateWorkflow.php b/src/workflow/ArcanistLiberateWorkflow.php
index c8aa224f..1a85cbbc 100644
--- a/src/workflow/ArcanistLiberateWorkflow.php
+++ b/src/workflow/ArcanistLiberateWorkflow.php
@@ -29,7 +29,8 @@ EOTEXT
         ->setHelp(
           pht('Perform a clean rebuild, ignoring caches. Thorough, but slow.')),
       $this->newWorkflowArgument('argv')
-        ->setWildcard(true),
+        ->setWildcard(true)
+        ->setIsPathArgument(true),
     );
   }