next-version.sh

#!/usr/bin/env bash
#
# Derive the next gobl.dev release tag.
#
# gobl.dev pins its major and minor to the github.com/invopop/gobl release it
# builds against, and owns the patch component for its own releases:
#
#   GOBL 0.505.x  ->  gobl.dev v0.505.0, v0.505.1, v0.505.2, ...
#   GOBL 0.506.0  ->  gobl.dev v0.506.0, v0.506.1, ...
#
# A GOBL patch release is absorbed into the next gobl.dev patch: if gobl.dev is
# already at v0.505.4 when GOBL 0.505.1 lands, the release carrying it is
# v0.505.5. The core patch is therefore not recoverable from the tag alone; it
# is recorded in the annotated tag message and the release notes, and
# `gobl version` reports it at runtime from the build info.
#
# Consumers who want a whole core line rather than an exact release can use the
# two-component form as a version *query* (it is not a valid version itself):
#
#   go get github.com/invopop/gobl.dev@v0.505
#
# Prints the next tag on stdout. Exits non-zero rather than emit a tag that
# would move the version backwards.
#
set -euo pipefail

RELEASE_RE='^v[0-9]+\.[0-9]+\.[0-9]+$'

# `go list -m` reports the version MVS actually selected, so the tag follows the
# core version really built even when a sibling addon module raises it above our
# own require line. It also honours any future replace directive, which grepping
# go.mod would not.
core="$(go list -m -f '{{.Version}}' github.com/invopop/gobl)"
if [[ ! "$core" =~ ^v[0-9]+\.[0-9]+\.[0-9]+ ]]; then
	echo "next-version: unexpected core version '$core'" >&2
	exit 1
fi

line="${core#v}"; line="${line%.*}" # v0.505.1 -> 0.505
line_re="${line//./\\.}"            # 0.505    -> 0\.505

# Highest release tag already on this core line.
latest="$(git tag -l "v${line}.*" | grep -E "^v${line_re}\.[0-9]+$" | sort -V | tail -n1 || true)"
if [[ -z "$latest" ]]; then
	next="v${line}.0" # first gobl.dev release on a new core line
else
	next="v${line}.$((${latest##*.} + 1))"
fi

# The module proxy and `@latest` both require versions to only ever increase.
# This trips if the GOBL requirement is ever moved backwards, in which case the
# fix is to roll forward rather than down.
top="$(git tag -l 'v*' | grep -E "$RELEASE_RE" | sort -V | tail -n1 || true)"
if [[ -n "$top" && "$(printf '%s\n%s\n' "$top" "$next" | sort -V | tail -n1)" != "$next" ]]; then
	echo "next-version: refusing $next, not above current highest $top (GOBL requirement downgraded?)" >&2
	exit 1
fi

echo "$next"