Provided by: sqitch_0.9996-1_all bug

Name

       App::Sqitch::Command - Sqitch Command support

Synopsis

         my $cmd = App::Sqitch::Command->load( deploy => \%params );
         $cmd->run;

Description

       App::Sqitch::Command is the base class for all Sqitch commands.

Interface

   Constants
       "ENGINES"

       Returns the list of supported engines, currently:

       •   "firebird"

       •   "mysql"

       •   "oracle"

       •   "pg"

       •   "sqlite"

       •   "vertica"

   Class Methods
       "options"

         my @spec = App::Sqitch::Command->options;

       Returns a list of Getopt::Long options specifications. When "load" loads the class, any
       options passed to the command will be parsed using these values. The keys in the resulting
       hash will be the first part of each option, with dashes converted to underscores. This
       hash will be passed to "configure" along with a App::Sqitch::Config object for munging
       into parameters to be passed to the constructor.

       Here's an example excerpted from the "config" command:

         sub options {
             return qw(
                 get
                 unset
                 list
                 global
                 system
                 config-file=s
             );
         }

       This will result in hash keys with the same names as each option except for
       "config-file=s", which will be named "config_file".

       "configure"

         my $params = App::Sqitch::Command->configure($config, $options);

       Takes two arguments, an App::Sqitch::Config object and the hash of command-line options as
       specified by "options". The returned hash should be the result of munging these two
       objects into a hash reference of parameters to be passed to the command subclass
       constructor.

       By default, this method converts dashes to underscores in command-line options keys, and
       then merges the configuration values with the options, with the command-line options
       taking priority. You may wish to override this method to do something different.

   Constructors
       "load"

         my $cmd = App::Sqitch::Command->load( \%params );

       A factory method for instantiating Sqitch commands. It loads the subclass for the
       specified command, uses the options returned by "options" to parse command-line options,
       calls "configure" to merge configuration with the options, and finally calls "new" with
       the resulting hash. Supported parameters are:

       "sqitch"
           The App::Sqitch object driving the whole thing.

       "config"
           An App::Sqitch::Config representing the current application configuration state.

       "command"
           The name of the command to be executed.

       "args"
           An array reference of command-line arguments passed to the command.

       "new"

         my $cmd = App::Sqitch::Command->new(%params);

       Instantiates and returns a App::Sqitch::Command object. This method is not designed to be
       overridden by subclasses; they should implement "BUILDARGS" or "BUILD", instead.

   Accessors
       "sqitch"

         my $sqitch = $cmd->sqitch;

       Returns the App::Sqitch object that instantiated the command. Commands may access its
       properties in order to manage global state.

   Overridable Instance Methods
       These methods should be overridden by all subclasses.

       "execute"

         $cmd->execute;

       Executes the command. This is the method that does the work of the command.  Must be
       overridden in all subclasses. Dies if the method is not overridden for the object on which
       it is called, or if it is called against a base App::Sqitch::Command object.

       "command"

         my $command = $cmd->command;

       The name of the command. Defaults to the last part of the package name, so as a rule you
       should not need to override it, since it is that string that Sqitch uses to find the
       command class.

   Utility Instance Methods
       These methods are mainly provided as utilities for the command subclasses to use.

       "default_target"

         my $target = $cmd->default_target;

       This method returns the default target. It should only be used by commands that don't use
       a "parse_args()" to find and load a target.

       This method should always return a target option, never "undef". If the "--engine" option
       or "core.engine" configuration option has been set, then the target will support that
       engine. In the latter case, if "engine.$engine.target" is set, that value will be used.
       Otherwise, the returned target will have a URI of "db:" and no associated engine; the
       "engine" method will throw an exception. This behavior should be fine for commands that
       don't need to load the engine.

       "parse_args"

         my ($name1, $name2, $targets, $changes) = $cmd->parse_args(
           names  => \@names,
           target => $target_name,
           args   => \@args
         );

       Examines each argument to determine whether it's a known change spec or identifies a
       target. Unrecognized arguments will replace false values in the "names" array reference.
       Any remaining unknown arguments will trigger an error.

       Returns a list consisting all the desired names, followed by an array reference of target
       objects and an array reference of change specs.

       This method is useful for commands that take a number of arguments where the order may be
       mixed.

       The supported parameters are:

       "args"
           An array reference of the command arguments.

       "target"
           The name of a target, if any. Useful for commands that offer their own "--target"
           option. This target will be the default target, and the first returned in the targets
           array.

       "names"
           An array reference of names. If any is false, its place will be taken by an otherwise
           unrecognized argument. The number of values in this array reference determines the
           number of values returned as names in the return values. Such values may still be
           false or undefined; it's up to the caller to decide what to do about that.

       "all"
           In the event that no targets are recognized (or changes that implicitly recognize the
           default target), if this parameter is true, then all known targets from the
           configuration will be returned.

       "no_changes"
           If true, the parser will not check to see if any argument corresponds to a change. The
           last value returned will be "undef" instead of the usual array reference. Any argument
           that might have been recognized as a change will instead be included in either the
           "targets" array -- if it's recognized as a target -- or used to set names to return.
           Any remaining are considered unknown arguments and will result in an exception.

       "no_default"
           If true, no default target will be returned, even if no other targets are found. See
           below for details.

       If a target parameter is passed, it will always be instantiated and returned as the first
       item in the "target" array, and arguments recognized as changes in the plan associated
       with that target will be returned as changes.

       If no target is passed or appears in the arguments, a default target will be instantiated
       based on the command-line options and configuration -- unless the "no_default" parameter
       is true. Unlike the target returned by "default_target", this target must have an
       associated engine specified by the "--engine" option or configuration. This is on the
       assumption that it will be used by commands that require an engine to do their work. Of
       course, any changes must be recognized from the plan associated with this target.

       Changes are only recognized if they're found in the plan of the target that precedes them.
       If no target precedes them, the target specified by the "target" parameter or the default
       target will be searched. Such changes can be specified in any way documented in
       sqitchchanges.

       Targets may be recognized by any one of these types of arguments:

       •   Target Name

       •   Database URI

       •   Engine Name

       •   Plan File

       In the case of plan files, "parse_args()" will return the first target it finds for that
       plan file, even if multiple targets use the same plan file. The order of precedence for
       this determination is the default project target, followed by named targets, then engine
       targets.

       "run"

         $cmd->run('echo hello');

       Runs a system command and waits for it to finish. Throws an exception on error.

       "capture"

         my @files = $cmd->capture(qw(ls -lah));

       Runs a system command and captures its output to "STDOUT". Returns the output lines in
       list context and the concatenation of the lines in scalar context.  Throws an exception on
       error.

       "probe"

         my $git_version = $cmd->capture(qw(git --version));

       Like "capture", but returns just the "chomp"ed first line of output.

       "verbosity"

         my $verbosity = $cmd->verbosity;

       Returns the verbosity level.

       "trace"

       Send trace information to "STDOUT" if the verbosity level is 3 or higher.  Trace messages
       will have "trace: " prefixed to every line. If it's lower than 3, nothing will be output.

       "debug"

         $cmd->debug('Found snuggle in the crib.');

       Send debug information to "STDOUT" if the verbosity level is 2 or higher.  Debug messages
       will have "debug: " prefixed to every line. If it's lower than 2, nothing will be output.

       "info"

         $cmd->info('Nothing to deploy (up-to-date)');

       Send informational message to "STDOUT" if the verbosity level is 1 or higher, which, by
       default, it is. Should be used for normal messages the user would normally want to see. If
       verbosity is lower than 1, nothing will be output.

       "comment"

         $cmd->comment('On database flipr_test');

       Send comments to "STDOUT" if the verbosity level is 1 or higher, which, by default, it is.
       Comments have "# " prefixed to every line. If verbosity is lower than 1, nothing will be
       output.

       "emit"

         $cmd->emit('core.editor=emacs');

       Send a message to "STDOUT", without regard to the verbosity. Should be used only if the
       user explicitly asks for output, such as for "sqitch config --get core.editor".

       "vent"

         $cmd->vent('That was a misage.');

       Send a message to "STDERR", without regard to the verbosity. Should be used only for error
       messages to be printed before exiting with an error, such as when reverting failed
       changes.

       "page"

         $sqitch->page('Search results:');

       Like "emit()", but sends the output to a pager handle rather than "STDOUT".  Unless there
       is no TTY (such as when output is being piped elsewhere), in which case it is sent to
       "STDOUT". Meant to be used to send a lot of data to the user at once, such as when display
       the results of searching the event log:

         $iter = $sqitch->engine->search_events;
         while ( my $change = $iter->() ) {
             $cmd->page(join ' - ', @{ $change }{ qw(change_id event change) });
         }

       "warn"

         $cmd->warn('Could not find nerble; using nobble instead.');

       Send a warning messages to "STDERR". Warnings will have "warning: " prefixed to every
       line. Use if something unexpected happened but you can recover from it.

       "usage"

         $cmd->usage('Missing "value" argument');

       Sends the specified message to "STDERR", followed by the usage sections of the command's
       documentation. Those sections may be named "Name", "Synopsis", or "Options". Any or all of
       these will be shown. The doc used to display them will be the first found of:

       "sqitch-$command-usage"
       "sqitch-$command"
       "sqitch"
       "App::Sqitch::Command::$command"
       "App::Sqitch::Command"

       For an ideal usage messages, "sqitch-$command-usage.pod" should be created by all command
       subclasses.

See Also

       sqitch
           The Sqitch command-line client.

Author

       David E. Wheeler <david@justatheory.com>

License

       Copyright (c) 2012-2015 iovation Inc.

       Permission is hereby granted, free of charge, to any person obtaining a copy of this
       software and associated documentation files (the "Software"), to deal in the Software
       without restriction, including without limitation the rights to use, copy, modify, merge,
       publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
       to whom the Software is furnished to do so, subject to the following conditions:

       The above copyright notice and this permission notice shall be included in all copies or
       substantial portions of the Software.

       THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
       INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
       PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
       FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
       OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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