[gentoo-dev] [PATCH v5] greadme.eclass: new eclass

[Florian Schmaus <flow@gentoo.org>]

This new eclass includes various improvements over the existing
readme.gentoo-r1.eclass.

First, the content of README.gentoo will only be shown on new
installations or if it has changed between updates.

Second, it allows the composition of readme via bash's heredoc.

And finally, the eclass exports phase functions, which helps to reduce
the boilerplate code in many cases.

I would like to thank ulm for assistance with the eclass' code.

Signed-off-by: Florian Schmaus <flow@gentoo.org>
---

Notes:
    - also show readme contents if FEATURES=nodoc

 eclass/greadme.eclass | 257 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 257 insertions(+)
 create mode 100644 eclass/greadme.eclass

diff --git a/eclass/greadme.eclass b/eclass/greadme.eclass
new file mode 100644
index 000000000000..4f0534200c1e
--- /dev/null
+++ b/eclass/greadme.eclass
@@ -0,0 +1,257 @@
+# Copyright 1999-2024 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+# @ECLASS: greadme.eclass
+# @MAINTAINER:
+# Florian Schmaus <flow@gentoo.org>
+# @AUTHOR:
+# Author: Florian Schmaus <flow@gentoo.org>
+# @SUPPORTED_EAPIS: 8
+# @BLURB: install a doc file, that will be conditionally shown via elog messages
+# @DESCRIPTION:
+# An eclass for installing a README.gentoo doc file with important
+# information for the user.  The content of README.gentoo will shown be
+# via elog messages either on fresh installations or if the contents of
+# the file have changed.  Furthermore, the README.gentoo file will be
+# installed under /usr/share/doc/${PF} for later consultation.
+#
+# This eclass was inspired by readme.gentoo-r1.eclass.  The main
+# differences are as follows.  Firstly, it only displays the doc file
+# contents if they have changed (unless GREADME_SHOW is set).
+# Secondly, it provides a convenient API to install the doc file via
+# stdin.
+#
+# @CODE
+# inherit greadme
+#
+# src_install() {
+#   ...
+#   greadme_stdin <<-EOF
+#   This is the content of the created readme doc file.
+#   EOF
+#   ...
+#   if use foo; then
+#     greadme_stdin --append <<-EOF
+#     This is conditional readme content, based on USE=foo.
+#     EOF
+#   fi
+# }
+# @CODE
+#
+# If the ebuild overrides the default pkg_preinst or respectively
+# pkg_postinst, then it must call greadme_pkg_preinst and
+# greadme_pkg_postinst explicitly.
+
+if [[ -z ${_GREADME_ECLASS} ]]; then
+_GREADME_ECLASS=1
+
+case ${EAPI} in
+	8) ;;
+	*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
+esac
+
+_GREADME_FILENAME="README.gentoo"
+_GREADME_TMP_FILE="${T}/${_GREADME_FILENAME}"
+_GREADME_REL_PATH="/usr/share/doc/${PF}/${_GREADME_FILENAME}"
+
+# @ECLASS_VARIABLE: GREADME_SHOW
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If set to "yes" then unconditionally show the contents of the readme
+# file in pkg_postinst via elog. If set to "no", then do not show the
+# contents of the readme file, even if they have changed.
+
+# @ECLASS_VARIABLE: GREADME_AUTOFORMATTING_DISABLED
+# @DEFAULT_UNSET
+# @DESCRIPTION:
+# If non-empty, the readme file will not be automatically formatted.
+
+# @FUNCTION: greadme_stdin
+# @USAGE: [--append]
+# @DESCRIPTION:
+# Create the readme doc via stdin.  You can use --append to append to an
+# existing readme doc.
+greadme_stdin() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local append
+	while [[ -n ${1} ]] && [[ ${1} == --* ]]; do
+		case ${1} in
+			--append)
+				append=1
+				shift
+				;;
+		esac
+	done
+
+	if [[ -n ${append} ]]; then
+		if [[ ! -f ${_GREADME_TMP_FILE} ]]; then
+			die "Gentoo README does not exist when trying to append to it"
+		fi
+
+		cat >> "${_GREADME_TMP_FILE}" || die
+	else
+		cat > "${_GREADME_TMP_FILE}" || die
+	fi
+
+	_greadme_install_doc
+}
+
+# @FUNCTION: greadme_file
+# @USAGE: <file>
+# @DESCRIPTION:
+# Installs the provided file as readme doc.
+greadme_file() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local input_doc_file="${1}"
+	if [[ -z ${input_doc_file} ]]; then
+		die "No file specified"
+	fi
+
+	cp "${input_doc_file}" "${_GREADME_TMP_FILE}" || die
+
+	_greadme_install_doc
+}
+
+# @FUNCTION: _greadme_install_doc
+# @INTERNAL
+# @DESCRIPTION:
+# Installs the readme file from the temp directory into the image.
+_greadme_install_doc() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	local greadme="${_GREADME_TMP_FILE}"
+	if [[ ! "${GREADME_AUTOFORMATTING_DISABLED}" ]]; then
+		greadme="${_GREADME_TMP_FILE}".formatted
+
+		# Use fold, followed by a sed to strip trailing whitespace.
+		# https://bugs.gentoo.org/460050#c7
+		fold -s -w 70 "${_GREADME_TMP_FILE}" |
+			sed 's/[[:space:]]*$//' > "${greadme}"
+		assert "failed to autoformat ${_GREADME_FILENAME}"
+	fi
+
+	# Subshell to avoid pollution of calling environment.
+	(
+		docinto .
+		newdoc "${greadme}" "${_GREADME_FILENAME}"
+	)
+
+	# Exclude the readme file from compression, so that its contents can
+	# be easily compared.
+	docompress -x "${_GREADME_REL_PATH}"
+
+	# Save the contents of the of the readme. Unfortunately we have to
+	# do this in src_* phase, because FEATURES=nodoc is applied right
+	# after src_install and not after pkg_preinst.
+	_GREADME_CONTENT=$(< "${greadme}")
+}
+
+# @FUNCTION: greadme_pkg_preinst
+# @DESCRIPTION:
+# Performs checks like comparing the readme doc from the image with a
+# potentially existing one in the live system.
+greadme_pkg_preinst() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ -z ${REPLACING_VERSIONS} ]]; then
+		_GREADME_SHOW="fresh-install"
+		return
+	fi
+
+	if [[ -v GREADME_SHOW ]]; then
+		case ${GREADME_SHOW} in
+			yes)
+				_GREADME_SHOW="forced"
+				;;
+			no)
+				_GREADME_SHOW=""
+				;;
+			*)
+				die "Invalid argument of GREADME_SHOW: ${GREADME_SHOW}"
+				;;
+		esac
+		return
+	fi
+
+	local image_greadme_file="${ED}${_GREADME_REL_PATH}"
+	if [[ ! -f ${image_greadme_file} ]]; then
+		if [[ -v _GREADME_CONTENT ]]; then
+			# There is no greadme in the image but the ebuild created
+			# one. This is likely because FEATURES=nodoc is active.
+			# Unconditionally show greadme's contents.
+			_GREADME_SHOW="nodoc-active"
+		else
+			# No README file was created by the ebuild.
+			_GREADME_SHOW=""
+		fi
+
+		return
+	fi
+
+	check_live_doc_file() {
+		local cur_pvr=$1
+		local live_greadme_file="${EROOT}/usr/share/doc/${PN}-${cur_pvr}/${_GREADME_FILENAME}"
+
+		if [[ ! -f ${live_greadme_file} ]]; then
+			_GREADME_SHOW="no-current-greadme"
+			return
+		fi
+
+		cmp -s "${live_greadme_file}" "${image_greadme_file}"
+		local ret=$?
+		case ${ret} in
+			0)
+				_GREADME_SHOW=""
+				;;
+			1)
+				_GREADME_SHOW="content-differs"
+				;;
+			*)
+				die "cmp failed with ${ret}"
+				;;
+		esac
+	}
+
+	local replaced_version
+	for replaced_version in ${REPLACING_VERSIONS}; do
+		check_live_doc_file ${replaced_version}
+
+		# Once _GREADME_SHOW is non empty, we found a reason to show the
+		# readme and we can abort the loop.
+		if [[ -n ${_GREADME_SHOW} ]]; then
+			break
+		fi
+	done
+}
+
+# @FUNCTION: greadme_pkg_postinst
+# @DESCRIPTION:
+# Conditionally shows the contents of the readme doc via elog.
+greadme_pkg_postinst() {
+	debug-print-function ${FUNCNAME} "${@}"
+
+	if [[ ! -v _GREADME_SHOW ]]; then
+		die "_GREADME_SHOW not set. Did you call greadme_pkg_preinst?"
+	fi
+
+	if [[ -z ${_GREADME_SHOW} ]]; then
+		# If _GREADME_SHOW is empty, then there is no reason to show the contents.
+		return
+	fi
+
+	local line
+	printf '%s\n' "${_GREADME_CONTENT}" | while read -r line; do
+		elog "${line}"
+	done
+	elog ""
+	elog "NOTE: Above message is only printed the first time package is"
+	elog "installed or if the message changed. Please look at"
+	elog "${EPREFIX}${_GREADME_REL_PATH}"
+	elog "for future reference."
+}
+
+fi
+
+EXPORT_FUNCTIONS pkg_preinst pkg_postinst
-- 
2.44.2