Cleaned up errors reporting.

README.md

@@ -77,7 +77,7 @@ squeezeBlank     | Same as `-s`                  | bool
 showNonPrinting  | Same as `-v`                  | bool
 
 * `paths` and `output` are required.
-* `output` should be an [IOSink](https://api.dart.dev/dart-io/IOSink-class.html) like `stdout` or a [File](https://api.dart.dev/dart-io/File/openWrite.html) stream.
+* `output` should be an [IOSink](https://api.dart.dev/dart-io/IOSink-class.html) such as `stdout` or a [File](https://api.dart.dev/dart-io/File/openWrite.html) stream.
 * `input` can be [stdin](https://api.dart.dev/dart-io/Stdin-class.html).
 
 The remaining optional parameters are similar to the [GNU cat](https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html#cat-invocation) utility.

bin/dcat.dart

@@ -22,6 +22,8 @@ const showTabsFlag = 'show-tabs';
 const squeezeBlank = 'squeeze-blank';
 const versionFlag = 'version';
 
+const _homePage = 'https://github.com/ethauvin/dcat';
+
 /// Concatenates files specified in [arguments].
 ///
 /// Usage: `dcat [option] [file]…`
@@ -33,8 +35,9 @@ Future<int> main(List<String> arguments) async {
   try {
     argResults = parser.parse(arguments);
   } on FormatException catch (e) {
-    return printError(
+    await printError(
         "${e.message}\nTry '$appName --$helpFlag' for more information.");
+    return exitFailure;
   }
 
   if (argResults[helpFlag]) {
@@ -121,20 +124,19 @@ Future<ArgParser> setupArgsParser() async {
   return parser;
 }
 
-/// Prints the error [message] to [stderr].
+/// Prints an error [message] to [stderr].
-Future<int> printError(String message) async {
+Future<void> printError(String message) async {
   stderr.writeln("$appName: $message");
-  return exitFailure;
 }
 
 /// Prints the version info.
 Future<int> printVersion() async {
   print('''$appName (Dart cat) $appVersion
 Copyright (C) 2021 Erik C. Thauvin
-License: 3-Clause BSD <https://opensource.org/licenses/BSD-3-Clause>
+License 3-Clause BSD: <https://opensource.org/licenses/BSD-3-Clause>
 
-Inspired by <https://dart.dev/tutorials/server/cmdline>
+Written by Erik C. Thauvin <https://erik.thauvin.net/>
-Written by Erik C. Thauvin <https://erik.thauvin.net/>''');
+Source: $_homePage''');
   return exitSuccess;
 }
 
@@ -150,6 +152,6 @@ Examples:
   $appName f - g  Output f's contents, then standard input, then g's contents.
   $appName        Copy standard input to standard output.
 
-Source and documentation: <https://github.com/ethauvin/dcat>''');
+Source and documentation: <$_homePage>''');
   return exitSuccess;
 }

doc/api/dcat/cat.html

@@ -88,14 +88,15 @@
     bool squeezeBlank = false,
     bool showNonPrinting = false}) async {
   final result = CatResult();
-  final lastLine = _LastLine(0, _lineFeed);
+  final lastLine = _LastLine();
+
   if (paths.isEmpty) {
     if (input != null) {
       try {
         await _writeStream(input, lastLine, output, showEnds, showLineNumbers,
             numberNonBlank, showTabs, squeezeBlank, showNonPrinting);
       } catch (e) {
-        result.addMessage(exitFailure, '$e');
+        result.addMessage(exitFailure, _formatError(e));
       }
     }
   } else {
@@ -109,20 +110,8 @@
         }
         await _writeStream(stream, lastLine, output, showEnds, showLineNumbers,
             numberNonBlank, showTabs, squeezeBlank, showNonPrinting);
-      } on FileSystemException catch (e) {
-        final String? osMessage = e.osError?.message;
-        final String message;
-        if (osMessage != null && osMessage.isNotEmpty) {
-          message = osMessage;
-        } else {
-          message = e.message;
-        }
-        result.addMessage(exitFailure, message, path: path);
-      } on FormatException {
-        result.addMessage(exitFailure, 'Binary file not supported.',
-            path: path);
       } catch (e) {
-        result.addMessage(exitFailure, '$e', path: path);
+        result.addMessage(exitFailure, _formatError(e), path: path);
       }
     }
   }

doc/api/index.html

@@ -97,7 +97,7 @@ if (result.isFailure) {
 <table><thead><tr><th style="text-align: left;">Parameter</th><th style="text-align: left;">Description</th><th style="text-align: left;">Type</th></tr></thead><tbody><tr><td style="text-align: left;">paths</td><td style="text-align: left;">The file paths.</td><td style="text-align: left;">String[]</td></tr><tr><td style="text-align: left;">output</td><td style="text-align: left;">The standard output or file.</td><td style="text-align: left;"><a href="https://api.dart.dev/dart-io/IOSink-class.html">IOSink</a></td></tr><tr><td style="text-align: left;">input</td><td style="text-align: left;">The standard input.</td><td style="text-align: left;"><a href="https://api.dart.dev/dart-io/Stdin-class.html">Stream</a></td></tr><tr><td style="text-align: left;">showEnds</td><td style="text-align: left;">Same as <code>-e</code></td><td style="text-align: left;">bool</td></tr><tr><td style="text-align: left;">numberNonBlank</td><td style="text-align: left;">Same as <code>-b</code></td><td style="text-align: left;">bool</td></tr><tr><td style="text-align: left;">showLineNumbers</td><td style="text-align: left;">Same as <code>-n</code></td><td style="text-align: left;">bool</td></tr><tr><td style="text-align: left;">showTabs</td><td style="text-align: left;">Same as <code>-T</code></td><td style="text-align: left;">bool</td></tr><tr><td style="text-align: left;">squeezeBlank</td><td style="text-align: left;">Same as <code>-s</code></td><td style="text-align: left;">bool</td></tr><tr><td style="text-align: left;">showNonPrinting</td><td style="text-align: left;">Same as <code>-v</code></td><td style="text-align: left;">bool</td></tr></tbody></table>
 <ul>
 <li><code>paths</code> and <code>output</code> are required.</li>
-<li><code>output</code> should be an <a href="https://api.dart.dev/dart-io/IOSink-class.html">IOSink</a> like <code>stdout</code> or a <a href="https://api.dart.dev/dart-io/File/openWrite.html">File</a> stream.</li>
+<li><code>output</code> should be an <a href="https://api.dart.dev/dart-io/IOSink-class.html">IOSink</a> such as <code>stdout</code> or a <a href="https://api.dart.dev/dart-io/File/openWrite.html">File</a> stream.</li>
 <li><code>input</code> can be <a href="https://api.dart.dev/dart-io/Stdin-class.html">stdin</a>.</li>
 </ul>
 <p>The remaining optional parameters are similar to the <a href="https://www.gnu.org/software/coreutils/manual/html_node/cat-invocation.html#cat-invocation">GNU cat</a> utility.</p>

lib/dcat.dart

@@ -45,10 +45,8 @@ class CatResult {
 
 // Holds the current line number and last character.
 class _LastLine {
-  int lineNumber;
+  int lineNumber = 0;
-  int lastChar;
+  int lastChar = _lineFeed;
-
-  _LastLine(this.lineNumber, this.lastChar);
 }
 
 /// Concatenates files in [paths] to the standard output or a file.
@@ -66,14 +64,15 @@ Future<CatResult> cat(List<String> paths, IOSink output,
     bool squeezeBlank = false,
     bool showNonPrinting = false}) async {
   final result = CatResult();
-  final lastLine = _LastLine(0, _lineFeed);
+  final lastLine = _LastLine();
+
   if (paths.isEmpty) {
     if (input != null) {
       try {
         await _writeStream(input, lastLine, output, showEnds, showLineNumbers,
             numberNonBlank, showTabs, squeezeBlank, showNonPrinting);
       } catch (e) {
-        result.addMessage(exitFailure, '$e');
+        result.addMessage(exitFailure, _formatError(e));
       }
     }
   } else {
@@ -87,26 +86,32 @@ Future<CatResult> cat(List<String> paths, IOSink output,
         }
         await _writeStream(stream, lastLine, output, showEnds, showLineNumbers,
             numberNonBlank, showTabs, squeezeBlank, showNonPrinting);
-      } on FileSystemException catch (e) {
-        final String? osMessage = e.osError?.message;
-        final String message;
-        if (osMessage != null && osMessage.isNotEmpty) {
-          message = osMessage;
-        } else {
-          message = e.message;
-        }
-        result.addMessage(exitFailure, message, path: path);
-      } on FormatException {
-        result.addMessage(exitFailure, 'Binary file not supported.',
-            path: path);
       } catch (e) {
-        result.addMessage(exitFailure, '$e', path: path);
+        result.addMessage(exitFailure, _formatError(e), path: path);
       }
     }
   }
   return result;
 }
 
+// Formats error message.
+String _formatError(Object e) {
+  final String message;
+  if (e is FileSystemException) {
+    final String? osMessage = e.osError?.message;
+    if (osMessage != null && osMessage.isNotEmpty) {
+      message = osMessage;
+    } else {
+      message = e.message;
+    }
+  } else if (e is FormatException) {
+    message = 'Binary file not supported.';
+  } else {
+    message = '$e';
+  }
+  return message;
+}
+
 // Writes parsed data from a stream
 Future<void> _writeStream(
     Stream stream,
@@ -118,9 +123,8 @@ Future<void> _writeStream(
     bool showTabs,
     bool squeezeBlank,
     bool showNonPrinting) async {
-  const tab = 9;
+  // No flags
-  int squeeze = 0;
+  if (!showEnds &&
-  final noFlags = !showEnds &&
       !showLineNumbers &&
       !numberNonBlank &&
       !showTabs &&
@@ -162,6 +166,7 @@ Future<void> _writeStream(
           }
         } else if (ch == tab) {
           if (showTabs) {
+            // TAB
             sb.write('^I');
             continue;
           }
@@ -183,6 +188,7 @@ Future<void> _writeStream(
               continue;
             }
           } else {
+            // CTRL
             sb
               ..write('^')
               ..writeCharCode(ch + 64);