#wren.com: Wren from a terminal

wren.exe is a program with a window. Typed in cmd or PowerShell it gives the prompt back at once and has no console of its own, so wren ctl ... shows nothing reliably and a script gets no exit code. wren.com is a small console program (src/tools/wrencom, about 150 KB, core library only) that sits beside wren.exe. cmd and PowerShell find wren.com before wren.exe when wren is typed (the order of PATHEXT), so the launcher is what runs.

wren ctl help                       :: text on the standard output, exit code 0
wren ctl nosuchcommand              :: message on the standard error output, exit code 4
wren ctl help > help.txt            :: redirections and pipes work: the launcher gives its own handles to wren.exe
wren ctl help | findstr run
wren https://example.org/           :: the window opens, the prompt comes back at once

#Wait or let go

The launcher starts wren.exe with the same arguments and decides from them (decide in src/tools/wrencom/plan.odin):

wren.exe reads ctl, help and version the same way: only the first argument (./ctl, ./help, ./version open a file or host of that name; after an option the word is refused with a message and exit code 2, never opened as https://help).

When it waits, it hands its own standard input, output and error to wren.exe (STARTF_USESTDHANDLES), so > file, 2> file, 2>&1 and | more act on what wren.exe prints. It also puts itself in a Job Object with KILL_ON_JOB_CLOSE: if the launcher is killed (terminal closed, build step cancelled), the Wren it started goes with it. Ctrl+C reaches both; the launcher stays until wren.exe ends so that it can return its code.

Its own failures use the shells' codes: 126 the launcher is named .exe (it would start itself) or wren.exe would not start, 127 there is no wren.exe beside it. The messages are English and begin with wren.com (Wren console launcher):; they are for a terminal, not part of Wren's interface, and the launcher imports nothing from Wren, so they are not in the i18n catalogue.

#Where it comes from and who writes it

• wrentool build (build.bat) compiles it to build\wren.com (-subsystem:console, before the browser).
• wren.exe embeds it (#load, src/browser/console_launcher.odin): the release stays one file.
• Setup writes it beside the installed wren.exe when "Add Wren to PATH" is ticked and removes it when it is unticked, when the integration is removed (--desktop-integration=remove) and when Wren is uninstalled or the installation is moved (src/desktop/launcher.odin). It is never written anywhere else, and never without the PATH entry that makes it reachable. --desktop-integration=install does the same for a copy that is not installed.
• It carries a mark ((Wren console launcher) in every message): a wren.com without it is another program's, and is neither replaced nor deleted. An installation that has the PATH entry but no wren.com (older Setup) is shown as "to repair" and Repair writes it.
• A launcher that is running cannot be overwritten or deleted: it is renamed to wren.com.old, and removed by the next write or removal (on uninstall it is reported with the other files a running program holds).

#Tests

• odin test src/tools/wrencom -vet: the decision (wait / let go), the target (wren.com to wren.exe, refusing a .exe), and the quoting of the command line (read back by CommandLineToArgvW).
• odin test src/desktop: Setup's side (written with the PATH option, replaced by a new version, removed with it, never over another program's file, removed with the install folder).
• src\tools\e2e\wrencom.odin (a step of test_all): the launcher and wren.exe copied into a scratch folder; ctl help, an unknown command, what > file, 2>, 2>&1 and | hand over to it, its exit code, --desktop-integration=status, the integration writing and removing wren.com, the refusals, an interface start that returns at once, --cli, and the death of the child with the launcher.

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