Open Xcode project and set active file from terminal - xcode

Question

Opening an Xcode project from the terminal is easy:
open Foo.xcodeproj/
But that just opens the project and resumes its previous state using UserInterfaceState.xcuserstate - so it just opens to the last active file you were editing.
Is there a way to open an Xcode project and specify which file it should open to?
What I've tried:
Editing .xcuserstate - nightmare, don't do it.
Running open Foo/Foo.xcodeproj/ then open Foo/Sources/main.swift which works some of the time, but not always. (If you just generated the project and do this, it'll open the project, then in a separate window it'll open the file.)
Any other ideas?

Answer 1

An Xcode engineer named Mike pointed me at the loaded property of Xcode's workspace document scripting class. By polling this, we can wait until Xcode has finished loading the project (including loading the editor pane) before asking it to open the file. This lets up reliably open the file in its project's window.
Here's the xopen script I wrote:
#!/bin/bash
shopt -s nullglob
sourceFile="$1"
case "$sourceFile" in
/*) ;;
*) sourceFile="$PWD"/"$sourceFile" ;;
esac
projectDir="$sourceFile"
while [[ $projectDir = */* ]]; do
projectDir="${projectDir%/*}"
candidates=("$projectDir"/*.xcodeproj)
candidate="${candidates[0]}"
if [[ "$candidate" != "" ]]; then
jPath="$candidate"
fi
done
if [[ "$jPath" = "" ]]; then
echo 1>&2 "error: couldn't find .xcodeproj in any parent directory"
exit 1
fi
exec osascript - "$jPath" "$sourceFile" <<EOF
on run argv
set jPath to item 1 of argv
set sourceFile to item 2 of argv
tell app "Xcode"
set wsDoc to (open jPath)
set waitCount to 0
repeat until wsDoc's loaded or waitCount ≥ 20
set waitCount to waitCount + 1
delay 1
end repeat
if wsDoc's loaded then
open sourceFile
end if
end tell
end run
EOF
This script uses the shell to walk up the directory tree from the source file (given as a command line argument) until it finds a directory containing an Xcode project package. Then it passes the path to the project and the path to the source file to an AppleScript. The AppleScript asks Xcode to open the project. If Xcode already has the project open, it'll just bring the existing project window to the front.
Next, the script polls Xcode until it reports that the workspace document is loaded, or until 20 seconds have elapsed.
Finally, if the workspace document is loaded, it asks Xcode to open the source file. Xcode will open the source file in the existing project window's editor.