79 lines
3.0 KiB
Go
79 lines
3.0 KiB
Go
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package terminal
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import "os"
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// This file has some annoying nonsense to, yet again, work around the
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// panicwrap hack.
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//
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// Specifically, typically when we're running Terraform the stderr handle is
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// not directly connected to the terminal but is instead a pipe into a parent
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// process gathering up the output just in case a panic message appears.
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// However, this package needs to know whether the _real_ stderr is connected
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// to a terminal and what its width is.
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//
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// To work around that, we'll first initialize the terminal in the parent
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// process, and then capture information about stderr into an environment
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// variable so we can pass it down to the child process. The child process
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// will then use the environment variable to pretend that the panicwrap pipe
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// has the same characteristics as the terminal that it's indirectly writing
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// to.
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//
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// This file has some helpers for implementing that awkward handshake, but the
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// handshake itself is in package main, interspersed with all of the other
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// panicwrap machinery.
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//
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// You might think that the code in helper/wrappedstreams could avoid this
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// problem, but that package is broken on Windows: it always fails to recover
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// the real stderr, and it also gets an incorrect result if the user was
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// redirecting or piping stdout/stdin. So... we have this hack instead, which
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// gets a correct result even on Windows and even with I/O redirection.
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// StateForAfterPanicWrap is part of the workaround for panicwrap that
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// captures some characteristics of stderr that the caller can pass to the
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// panicwrap child process somehow and then use ReinitInsidePanicWrap.
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func (s *Streams) StateForAfterPanicWrap() *PrePanicwrapState {
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return &PrePanicwrapState{
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StderrIsTerminal: s.Stderr.IsTerminal(),
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StderrWidth: s.Stderr.Columns(),
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}
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}
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// ReinitInsidePanicwrap is part of the workaround for panicwrap that
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// produces a Streams containing a potentially-lying Stderr that might
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// claim to be a terminal even if it's actually a pipe connected to the
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// parent process.
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//
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// That's an okay lie in practice because the parent process will copy any
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// data it recieves via that pipe verbatim to the real stderr anyway. (The
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// original call to Init in the parent process should've already done any
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// necessary modesetting on the Stderr terminal, if any.)
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//
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// The state argument can be nil if we're not running in panicwrap mode,
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// in which case this function behaves exactly the same as Init.
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func ReinitInsidePanicwrap(state *PrePanicwrapState) (*Streams, error) {
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ret, err := Init()
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if err != nil {
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return ret, err
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}
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if state != nil {
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// A lying stderr, then.
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ret.Stderr = &OutputStream{
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File: ret.Stderr.File,
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isTerminal: func(f *os.File) bool {
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return state.StderrIsTerminal
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},
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getColumns: func(f *os.File) int {
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return state.StderrWidth
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},
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}
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}
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return ret, nil
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}
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// PrePanicwrapState is a horrible thing we use to work around panicwrap,
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// related to both Streams.StateForAfterPanicWrap and ReinitInsidePanicwrap.
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type PrePanicwrapState struct {
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StderrIsTerminal bool
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StderrWidth int
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}
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