Better handling of .arcconfig files.

Summary:
Throw a useful error message when an `.arcconfig` file is not valid JSON.

Depends on D9697.

Test Plan:
Modified an `.arcconfig` file to be invalid JSON.

```
> arc lint
Usage Exception: Your '~/.arcrc' file is not a valid JSON file.

Parse error on line 18 at column 4: Expected: 'STRING' - It appears you have an extra trailing comma
```

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9681

src/configuration/ArcanistConfigurationManager.php

@@ -63,13 +63,13 @@ public function getConfigFromAnySource($key, $default = null) {
   }
 
   /**
-   * For the advanced case where you want customized configuratin handling.
+   * For the advanced case where you want customized configuration handling.
    *
    * Reads the configuration from all available sources, returning a map (array)
    * of results, with the source as key. Missing values will not be in the map,
    * so an empty array will be returned if no results are found.
    *
-   * The map is ordered by the cannonical sources precedence, which is:
+   * The map is ordered by the canonical sources precedence, which is:
    * runtime > local > project > user > system
    *
    * @param key   Key to read
@@ -198,10 +198,12 @@ public function readUserConfigurationFile() {
         }
 
         $user_config_data = Filesystem::readFile($user_config_path);
-        $user_config = json_decode($user_config_data, true);
-        if (!is_array($user_config)) {
-          throw new ArcanistUsageException(
-            "Your '~/.arcrc' file is not a valid JSON file.");
+        try {
+          $user_config = phutil_json_decode($user_config_data);
+        } catch (PhutilJSONParserException $ex) {
+          throw new PhutilProxyException(
+            "Your '~/.arcrc' file is not a valid JSON file.".
+            $ex);
         }
       } else {
         $console->writeLog(
@@ -290,8 +292,14 @@ public function readSystemArcConfig() {
             'Config: Reading system configuration file "%s"...',
             $system_config_path));
         $file = Filesystem::readFile($system_config_path);
-        if ($file) {
-          $system_config = json_decode($file, true);
+        try {
+          $system_config = phutil_json_decode($file);
+        } catch (PhutilJSONParserException $ex) {
+          throw new PhutilProxyException(
+            pht(
+              "Your '%s' file is not a valid JSON file.",
+              $system_config_path),
+            $ex);
         }
       } else {
         $console->writeLog(
@@ -324,7 +332,7 @@ public function applyRuntimeArcConfig($args) {
     return $this->runtimeConfig;
   }
 
-    public function readDefaultConfig() {
+  public function readDefaultConfig() {
     $settings = new ArcanistSettings();
     return $settings->getDefaultSettings();
   }

src/workingcopyidentity/ArcanistWorkingCopyIdentity.php

@@ -201,17 +201,13 @@ public static function newFromRootAndConfigFile(
   }
 
   private static function parseRawConfigFile($raw_config, $from_where) {
-    $proj = json_decode($raw_config, true);
-
-    if (!is_array($proj)) {
-      throw new Exception(
-        "Unable to parse '.arcconfig' file '{$from_where}'. The file contents ".
-        "should be valid JSON.\n\n".
-        "FILE CONTENTS\n".
-        substr($raw_config, 0, 2048));
+    try {
+      return phutil_json_decode($raw_config);
+    } catch (PhutilJSONParserException $ex) {
+      throw new PhutilProxyException(
+        pht("Unable to parse '.arcconfig' file '%s'.", $from_where),
+        $ex);
     }
-
-    return $proj;
   }
 
   private function __construct($root, array $config) {
@@ -297,15 +293,13 @@ public function getProjectConfig($key, $default = null) {
    *
    * @task config
    */
-  public function getLocalConfig($key, $default=null) {
+  public function getLocalConfig($key, $default = null) {
     return idx($this->localConfig, $key, $default);
   }
 
   public function readLocalArcConfig() {
     if (strlen($this->localMetaDir)) {
-      $local_path = Filesystem::resolvePath(
-        'arc/config',
-        $this->localMetaDir);
+      $local_path = Filesystem::resolvePath('arc/config', $this->localMetaDir);
 
       $console = PhutilConsole::getConsole();
 
@@ -316,9 +310,12 @@ public function readLocalArcConfig() {
             'Config: Reading local configuration file "%s"...',
             $local_path));
 
-        $file = Filesystem::readFile($local_path);
-        if ($file) {
-          return json_decode($file, true);
+        try {
+          return phutil_json_decode($local_path);
+        } catch (PhutilJSONParserException $ex) {
+          throw new PhutilProxyException(
+            pht("Failed to parse '%s' as JSON.", $local_path),
+            $ex);
         }
       } else {
         $console->writeLog(
@@ -327,8 +324,8 @@ public function readLocalArcConfig() {
             'Config: Did not find local configuration at "%s".',
             $local_path));
       }
-
     }
+
     return array();
   }