bootstrap/specs/mix/runner

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#!/usr/bin/env bash
# Exit immediately if the script encounters a non-zero status.
set -e
# If set, Bash includes filenames beginning with a `.` in the results of
# filename expansion. The filenames `.` and `..` must always be matched
# explicitly, even if dotglob is set.
shopt -s dotglob
# ============================================================
# PROLOGUE
# ============================================================
# Create a new top-level directory as fallback in case $BUILD (defined below)
# is ever empty.
mkdir -p "/tmp/bs.mix"
# Create an intermediate build directory. The final step of this script will
# copy the content from this directory to $OUT.
BUILD=$(mktemp -d -p "/tmp/bs.mix")
if [ -z "$BUILD" ]; then
>&2 echo "Failed to create temp directory."
exit 1
fi
# Deletes the intermediate build directory on exit. We use a concatenation of
# the intermediate directory with the basename of the generated temp directory
# to ensure we never evaluate to root (i.e. `/`). That should never actually
# happen but a good habit to establish nonetheless.
function cleanup {
rm -r "/tmp/bs.mix/$(basename "$BUILD")"
}
trap cleanup EXIT
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# ============================================================
# ENVIRONMENT
# ============================================================
# Trims away any whitespace around the module name.
MODULE=$(echo "$MODULE" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
if [ -z "$MODULE" ]; then
MODULE_ARG=
else
MODULE_ARG="--module '$MODULE'"
fi
# ============================================================
# BUILD
# ============================================================
# Copy template contents over to the intermediate build directory.
cp -r template/* "$BUILD"
# Explicitly set permissions on all copied files.
find "$BUILD" -type f -execdir chmod 644 {} +
find "$BUILD" -type d -execdir chmod 755 {} +
# Generate a new project with the specified name using `mix`. Generate in a
# subdirectory to avoid interactive conflict resolution.
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nix develop "$BUILD" \
--command bash \
-c "mix new $BUILD/project --app '$APP' $MODULE_ARG"
# Copy the generated files into the intermediate build directory.
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mv -f "$BUILD"/project/* "$BUILD"
rmdir "$BUILD"/project
# Overwrite the generated README in favor of that defined in our template.
cp template/README.md "$BUILD"
chmod 644 "$BUILD"/README.md
# Replace the template name found in the flake.nix file. The mix generator would
# fail if $APP did not consist of just lowercase ASCII letters, numbers, or
# underscores. Thus $APP is safe to interpolate into the following command.
sed -i "s/<APP_NAME>/$APP/g" "$BUILD/flake.nix"
# ============================================================
# EPILOGUE
# ============================================================
# Success! Copy contents to target directory.
cp -r "$BUILD"/* "$OUT"