feature(json_annotation): get the message from FormatException

Improves error output with improperly formatted URIs, for example

Fixes #233

Author: kevmoo

json_annotation/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.2.9
+
+* When `FormatException` is caught in "checked mode", use the `message`
+  property when creating `CheckedFromJsonException`.
+
 ## 0.2.8
 
 * Added `$checkKeys` helper function and deprecated `$checkAllowedKeys`.

json_annotation/lib/src/checked_helpers.dart

@@ -96,6 +96,12 @@ class CheckedFromJsonException implements Exception {
       return error.message?.toString();
     } else if (error is BadKeyException) {
       return error.message;
+    } else if (error is FormatException) {
+      var message = error.message;
+      if (error.offset != null) {
+        message = '$message at offset ${error.offset}.';
+      }
+      return message;
     }
     return null;
   }

json_annotation/pubspec.yaml

@@ -1,5 +1,5 @@
 name: json_annotation
-version: 0.2.8
+version: 0.2.9-dev
 description: >-
   Classes and helper functions that support JSON code generation via the
   `json_serializable` package.

json_serializable/pubspec.yaml

@@ -13,7 +13,7 @@ dependencies:
 
   # Use a tight version constraint to ensure that a constraint on
   # `json_annotation`. Properly constrains all features it provides.
-  json_annotation: '>=0.2.8 <0.2.9'
+  json_annotation: '>=0.2.9 <0.2.10'
   meta: ^1.1.0
   path: ^1.3.2
   source_gen: ^0.8.2
@@ -27,3 +27,7 @@ dev_dependencies:
   logging: ^0.11.3+1
   test: ^1.0.0
   yaml: ^2.1.13
+
+dependency_overrides:
+  json_annotation:
+    path: ../json_annotation

json_serializable/test/yaml/yaml_test.dart

@@ -140,7 +140,7 @@ builders:
   builder_name:
     builder_factories: ["scssBuilder"]
     configLocation: "user@host:invalid/uri"''':
-      '''line 4, column 21 of file.yaml: Could not create `Builder`. Unsupported value for `configLocation`.
+      '''line 4, column 21 of file.yaml: Could not create `Builder`. Unsupported value for `configLocation`. Illegal scheme character at offset 4.
     configLocation: "user@host:invalid/uri"
                     ^^^^^^^^^^^^^^^^^^^^^^^'''
 };