If stdin is closed cursorPosition throws a RangeError about dart_console HOT 4 OPEN

So a use case on this one is difficult. I've exposed components of dart_console in my DCli library. DCli is a library which allows users to build cli applications. As such there is no single use case. My objective is to design a library that is easy to use and intuitive. DCli does implement a progress bar. ``` final term = Terminal(); final percentage = Format.percentage(progress.progress, 1); if (term.isAnsi) { term ..clearLine() ..startOfLine(); echo( '${EnumHelper.getName(progress.status).padRight(15)}${Format.bytesAsReadable (progress.downloaded)}/${Format.bytesAsReadable(progress.length)} $ percentage'); } else { if (_progressSuppressor % 1000 == 0 || progress.status == FetchStatus.complete) { print( '${EnumHelper.getName(progress.status).padRight(15)}${Format.bytesAsReadable (progress.downloaded)}/${Format.bytesAsReadable(progress.length)} $ percentage'); } _progressSuppressor++; if (_progressSuppressor > 1000) { _progressSuppressor = 0; } } ``` I also return default values for column and row: int get columns { if (hasTerminal) { return _console.windowWidth; } else { return 80; } } /// Returns the row location of the cursor. /// The first row is row 0. int get row => _cursor?.row ?? 24; If someone attempts to retrieve the cursor position I return null: Coordinate? get _cursor { /// attempting to get the cursor position if /// we don't have a terminal will hang the app /// as to obtain the cursor we must read from the /// terminal. if (hasTerminal && Ansi.isSupported) { try { return _console.cursorPosition; // ignore: avoid_catching_errors } on RangeError catch (_) { // if stdin is closed (seems to be within docker) // then the call to cursorPosition will fail. // RangeError: Invalid value: Not in inclusive range 0..1114111: -1 // new String.fromCharCode (dart:core-patch/string_patch.dart:45) // Console.cursorPosition (package:dart_console/src/console.dart:304) return null; } } else { return null; } } I have used dart_console in a couple of other apps I've built on to DCli that use the dart. critical_test uses the library to output progress messages on a single line (e.g. each time it runs a test it updates the same line with the name of the test, no. of failures and successes so far). I also have a classic progress bar in one of my apps. Here is the main class I expose: import 'dart:io'; import 'package:dart_console/dart_console.dart'; import 'ansi.dart'; /// /// Modes available when clearing a screen or line. /// /// When used with clearScreen: /// [all] - clears the entire screen /// [fromCursor] - clears from the cursor until the end of the screen /// [toCursor] - clears from the start of the screen to the cursor. /// /// When used with clearLine: /// [all] - clears the entire line /// [fromCursor] - clears from the cursor until the end of the line. /// [toCursor] - clears from the start of the line to the cursor. /// enum TerminalClearMode { // scrollback, /// clear whole screen all, /// clear screen from the cursor to the bottom of the screen. fromCursor, /// clear screen from the top of the screen to the cursor toCursor } /// Provides access to the Ansi Terminal. class Terminal { /// Factory ctor to get a Termainl factory Terminal() => _self; // ignore: flutter_style_todos /// TODO(bsutton): if we don't have a terminal or ansi isn't support /// we need to suppress any ansi codes being output. Terminal._internal(); static final _self = Terminal._internal(); final _console = Console(); /// Returns true if ansi escape characters are supported. bool get isAnsi => Ansi.isSupported; /// Clears the screen. /// If ansi escape sequences are not supported this is a no op. /// This call does not update the cursor position so in most /// cases you will want to call [home] after calling [clearScreen]. /// ```dart /// Terminal() /// ..clearScreen() /// ..home(); /// ``` void clearScreen({TerminalClearMode mode = TerminalClearMode.all}) { switch (mode) { // case AnsiClearMode.scrollback: // write('${esc}3J', newline: false); // break; case TerminalClearMode.all: _console.clearScreen(); break; case TerminalClearMode.fromCursor: write('${Ansi.esc}0Jm'); break; case TerminalClearMode.toCursor: write('${Ansi.esc}1Jm'); break; } } /// Clears the current line, moves the cursor to column 0 /// and then prints [text] effectively overwriting the current /// console line. /// If the current console doesn't support ansi escape /// sequences ([isAnsi] == false) then this call /// will simply revert to calling [print]. void overwriteLine(String text) { clearLine(); column = 0; _console.write(text); } /// Writes [text] to the terminal at the current /// cursor location without appending a newline character. void write(String text) { _console.write(text); } /// Writes [text] to the console followed by a newline. /// You can control the alignment of [text] by passing the optional /// [alignment] argment which defaults to left alignment. /// The alignment is based on the current terminals width with /// spaces inserted to the left of the string to facilitate the alignment. /// Make certain the current line is clear and the cursor is at column 0 /// before calling this method otherwise the alignment will not work /// as expected. void writeLine(String text, {TextAlignment alignment = TextAlignment.left}) => _console.writeLine(text, alignment); /// Clears the current console line without moving the cursor. /// If you want to write over the current line then /// call [clearLine] followed by [startOfLine] and then /// use [write] rather than print as it will leave /// the cursor on the current line. /// Alternatively use [overwriteLine]; void clearLine({TerminalClearMode mode = TerminalClearMode.all}) { switch (mode) { // case AnsiClearMode.scrollback: case TerminalClearMode.all: _console.eraseLine(); break; case TerminalClearMode.fromCursor: _console.eraseCursorToEnd(); break; case TerminalClearMode.toCursor: write('${Ansi.esc}1K'); break; } } /// show/hide the cursor void showCursor({required bool show}) { if (show) { _console.showCursor(); } else { _console.hideCursor(); } } /// Moves the cursor to the start of previous line. @deprecated('Use [cursorUp]') static void previousLine() { Terminal().cursorUp(); } /// Moves the cursor up one row void cursorUp() => _console.cursorUp(); /// Moves the cursor down one row void cursorDown() => _console.cursorDown(); /// Moves the cursor to the left one column void cursorLeft() => _console.cursorUp(); /// Moves the cursor to the right one column void cursorRight() => _console.cursorRight(); /// Returns the column location of the cursor int get column => _cursor?.col ?? 0; /// moves the cursor to the given column /// 0 is the first column // ignore: avoid_setters_without_getters set column(int column) { _console.cursorPosition = Coordinate(row, 0); } /// Moves the cursor to the start of line. void startOfLine() { column = 0; } /// The width of the terminal in columns. /// Where a column is one character wide. /// If no terminal is attached to a value of 80 is returned. /// This value can change if the users resizes the console window. int get columns { if (hasTerminal) { return _console.windowWidth; } else { return 80; } } /// Returns the row location of the cursor. /// The first row is row 0. int get row => _cursor?.row ?? 24; /// moves the cursor to the given row /// 0 is the first row set row(int row) { _console.cursorPosition = Coordinate(row, column); } Coordinate? get _cursor { /// attempting to get the cursor position if /// we don't have a terminal will hang the app /// as to obtain the cursor we must read from the /// terminal. if (hasTerminal && Ansi.isSupported) { try { return _console.cursorPosition; // ignore: avoid_catching_errors } on RangeError catch (_) { // if stdin is closed (seems to be within docker) // then the call to cursorPosition will fail. // RangeError: Invalid value: Not in inclusive range 0..1114111: -1 // new String.fromCharCode (dart:core-patch/string_patch.dart:45) // Console.cursorPosition (package:dart_console/src/console.dart:304) return null; } } else { return null; } } /// Whether a terminal is attached to stdin. bool get hasTerminal => stdin.hasTerminal; /// The height of the terminal in rows. /// Where a row is one character high. /// If no terminal is attached to stdout, a [StdoutException] is thrown. /// This value can change if the users resizes the console window. int get rows { if (hasTerminal) { return _console.windowHeight; } else { return 24; } } /// Sets the cursor to the top left corner /// of the screen (0,0) void home() => _console.resetCursorPosition(); /// Returns the current console height in rows. @deprecated('Use rows') int get lines => rows; } S. 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