logic_or.go

// scriptish is a library to help you port bash scripts to Golang
//
// inspired by:
//
// - http://labix.org/pipe
// - https://github.com/bitfield/script
//
// Copyright 2019-present Ganbaro Digital Ltd
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
//   * Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//
//   * Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in
//     the documentation and/or other materials provided with the
//     distribution.
//
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//     contributors may be used to endorse or promote products derived
//     from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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package scriptish

import "io"

// Or executes the given sequence only if the previous command has returned
// some kind of error.
//
// The sequence starts with an empty Stdin. The sequence's output is written
// back to the Stdout and Stderr of the calling list or pipeline - along
// with the StatusCode() and Error().
//
// It is an emulation of UNIX shell scripting's `list1 || command`
func Or(sq *Sequence, opts ...*StepOption) *SequenceStep {
	// we're going to wrap our sequences up as a Scriptish Command
	return NewSequenceStep(
		func(p *Pipe) (int, error) {
			// do we need to do anything?
			statusCode, err := p.StatusError()
			if err == nil {
				// debugging support
				Tracef("Or(): not executing the given sequence")

				// make sure we do not lose the output of the sequence so far
				p.DrainStdinToStdout()

				// all done
				return statusCode, err
			}

			// debugging support
			Tracef("Or(): executing the given sequence")

			// get our parameters
			params := getParamsFromEnv(p.Env)

			// run it
			sq.Exec(params...)

			// copy the results into our pipe
			io.Copy(p.Stdout, sq.Pipe.Stdout)
			io.Copy(p.Stderr, sq.Pipe.Stderr)

			// all done
			return sq.StatusCode(), sq.Error()
		},
		opts...,
	)
}