Reflow and format help message (#133)

Use concatenated `''` rather than `'''` so that we can break lines
separately in the source from where we want them broken in the output

Author: natebosch

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.4+1
+
+* Give more information when `dartfmt` fails.
+
 ## 0.5.4
 
 * Update to latest `build`, `build_runner`, and `build_test` releases.

lib/src/builder.dart

@@ -78,10 +78,12 @@ class GeneratorBuilder extends Builder {
       genPartContent = formatter.format(genPartContent);
     } catch (e, stack) {
       buildStep.logger.severe(
-          '''Error formatting generated source code for ${library.identifier}
-which was output to ${_generatedFile(buildStep.inputId).path}.\n
-This may indicate an issue in the generated code or in the formatter.\n
-Please check the generated code and file an issue on source_gen if appropriate.''',
+          'Error formatting generated source code for ${library.identifier}'
+          'which was output to ${_generatedFile(buildStep.inputId).path}.\n'
+          'This may indicate an issue in the generated code or in the '
+          'formatter.\n'
+          'Please check the generated code and file an issue on source_gen if '
+          'appropriate.',
           e,
           stack);
     }

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 0.5.4
+version: 0.5.4+1
 author: Dart Team <[email protected]>
 description: Automatic sourcecode generation for Dart
 homepage: https://github.com/dart-lang/source_gen