summaryrefslogtreecommitdiff
blob: 064e4b593589cb81c734092987e77ab0ff911644 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
# Copyright 1999-2012 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: /var/cvsroot/gentoo-x86/eclass/haskell-cabal.eclass,v 1.37 2012/11/19 21:27:56 slyfox Exp $

# @ECLASS: haskell-cabal.eclass
# @MAINTAINER:
# Haskell herd <haskell@gentoo.org>
# @AUTHOR:
# Original author: Andres Loeh <kosmikus@gentoo.org>
# Original author: Duncan Coutts <dcoutts@gentoo.org>
# @BLURB: for packages that make use of the Haskell Common Architecture for Building Applications and Libraries (cabal)
# @DESCRIPTION:
# Basic instructions:
#
# Before inheriting the eclass, set CABAL_FEATURES to
# reflect the tools and features that the package makes
# use of.
#
# Currently supported features:
#   haddock    --  for documentation generation
#   hscolour   --  generation of colourised sources
#   hoogle     --  generation of documentation search index
#   alex       --  lexer/scanner generator
#   happy      --  parser generator
#   c2hs       --  C interface generator
#   cpphs      --  C preprocessor clone written in Haskell
#   profile    --  if package supports to build profiling-enabled libraries
#   bootstrap  --  only used for the cabal package itself
#   bin        --  the package installs binaries
#   lib        --  the package installs libraries
#   nocabaldep --  don't add dependency on cabal.
#                  only used for packages that _must_ not pull the dependency
#                  on cabal, but still use this eclass (e.g. haskell-updater).
#   test-suite --  add support for cabal test-suites (introduced in Cabal-1.8)

inherit ghc-package multilib

# @ECLASS-VARIABLE: CABAL_EXTRA_CONFIGURE_FLAGS
# @DESCRIPTION:
# User-specified additional parameters passed to 'setup configure'.
# example: /etc/make.conf: CABAL_EXTRA_CONFIGURE_FLAGS=--enable-shared
: ${CABAL_EXTRA_CONFIGURE_FLAGS:=}

# @ECLASS-VARIABLE: CABAL_EXTRA_BUILD_FLAGS
# @DESCRIPTION:
# User-specified additional parameters passed to 'setup build'.
# example: /etc/make.conf: CABAL_EXTRA_BUILD_FLAGS=-v
: ${CABAL_EXTRA_BUILD_FLAGS:=}

# @ECLASS-VARIABLE: GHC_BOOTSTRAP_FLAGS
# @DESCRIPTION:
# User-specified additional parameters for ghc when building
# _only_ 'setup' binary bootstrap.
# example: /etc/make.conf: GHC_BOOTSTRAP_FLAGS=-dynamic to make
# linking 'setup' faster.
: ${GHC_BOOTSTRAP_FLAGS:=}

# @ECLASS-VARIABLE: CABAL_DEBUG_LOOSENING
# @DESCRIPTION:
# Show debug output for 'cabal_chdeps' function if set.
# Needs working 'diff'.
: ${CABAL_DEBUG_LOOSENING:=}

HASKELL_CABAL_EXPF="pkg_setup src_compile src_test src_install"

case "${EAPI:-0}" in
	2|3|4|5) HASKELL_CABAL_EXPF+=" src_configure" ;;
	*) ;;
esac

EXPORT_FUNCTIONS ${HASKELL_CABAL_EXPF}

for feature in ${CABAL_FEATURES}; do
	case ${feature} in
		haddock)    CABAL_USE_HADDOCK=yes;;
		hscolour)   CABAL_USE_HSCOLOUR=yes;;
		hoogle)     CABAL_USE_HOOGLE=yes;;
		alex)       CABAL_USE_ALEX=yes;;
		happy)      CABAL_USE_HAPPY=yes;;
		c2hs)       CABAL_USE_C2HS=yes;;
		cpphs)      CABAL_USE_CPPHS=yes;;
		profile)    CABAL_USE_PROFILE=yes;;
		bootstrap)  CABAL_BOOTSTRAP=yes;;
		bin)        CABAL_HAS_BINARIES=yes;;
		lib)        CABAL_HAS_LIBRARIES=yes;;
		nocabaldep) CABAL_FROM_GHC=yes;;
		test-suite) CABAL_TEST_SUITE=yes;;
		*) CABAL_UNKNOWN="${CABAL_UNKNOWN} ${feature}";;
	esac
done

if [[ -n "${CABAL_USE_HADDOCK}" ]]; then
	IUSE="${IUSE} doc"
	# don't require depend on itself to build docs.
	# ebuild bootstraps docs from just built binary
	[[ ${CATEGORY}/${PN} = "dev-haskell/haddock" ]] || DEPEND="${DEPEND} doc? ( dev-haskell/haddock )"
fi

if [[ -n "${CABAL_USE_HSCOLOUR}" ]]; then
	IUSE="${IUSE} hscolour"
	DEPEND="${DEPEND} hscolour? ( dev-haskell/hscolour )"
fi

if [[ -n "${CABAL_USE_ALEX}" ]]; then
	DEPEND="${DEPEND} dev-haskell/alex"
fi

if [[ -n "${CABAL_USE_HAPPY}" ]]; then
	DEPEND="${DEPEND} dev-haskell/happy"
fi

if [[ -n "${CABAL_USE_C2HS}" ]]; then
	DEPEND="${DEPEND} dev-haskell/c2hs"
fi

if [[ -n "${CABAL_USE_CPPHS}" ]]; then
	DEPEND="${DEPEND} dev-haskell/cpphs"
fi

if [[ -n "${CABAL_USE_PROFILE}" ]]; then
	IUSE="${IUSE} profile"
fi

if [[ -n "${CABAL_TEST_SUITE}" ]]; then
	IUSE="${IUSE} test"
fi

# We always use a standalone version of Cabal, rather than the one that comes
# with GHC. But of course we can't depend on cabal when building cabal itself.
if [[ -z ${CABAL_MIN_VERSION} ]]; then
	CABAL_MIN_VERSION=1.1.4
fi
if [[ -z "${CABAL_BOOTSTRAP}" && -z "${CABAL_FROM_GHC}" ]]; then
	DEPEND="${DEPEND} >=dev-haskell/cabal-${CABAL_MIN_VERSION}"
fi

# Libraries require GHC to be installed.
if [[ -n "${CABAL_HAS_LIBRARIES}" ]]; then
	RDEPEND="${RDEPEND} dev-lang/ghc"
fi

# returns the version of cabal currently in use
_CABAL_VERSION_CACHE=""
cabal-version() {
	if [[ -z "${_CABAL_VERSION_CACHE}" ]]; then
		if [[ "${CABAL_BOOTSTRAP}" ]]; then
			# We're bootstrapping cabal, so the cabal version is the version
			# of this package itself.
			_CABAL_VERSION_CACHE="${PV}"
		elif [[ "${CABAL_FROM_GHC}" ]]; then
			local cabal_package=$(echo "$(ghc-libdir)"/Cabal-*)
			# /path/to/ghc/Cabal-${VER} -> ${VER}
			_CABAL_VERSION_CACHE="${cabal_package/*Cabal-/}"
		else
			# We ask portage, not ghc, so that we only pick up
			# portage-installed cabal versions.
			_CABAL_VERSION_CACHE="$(ghc-extractportageversion dev-haskell/cabal)"
		fi
	fi
	echo "${_CABAL_VERSION_CACHE}"
}

cabal-bootstrap() {
	local setupmodule
	local cabalpackage
	if [[ -f "${S}/Setup.lhs" ]]; then
		setupmodule="${S}/Setup.lhs"
	elif [[ -f "${S}/Setup.hs" ]]; then
		setupmodule="${S}/Setup.hs"
	else
		die "No Setup.lhs or Setup.hs found"
	fi

	if [[ -z "${CABAL_BOOTSTRAP}" && -z "${CABAL_FROM_GHC}" ]] && ! ghc-sanecabal "${CABAL_MIN_VERSION}"; then
		eerror "The package dev-haskell/cabal is not correctly installed for"
		eerror "the currently active version of ghc ($(ghc-version)). Please"
		eerror "run haskell-updater or re-build dev-haskell/cabal."
		die "cabal is not correctly installed"
	fi

	# We build the setup program using the latest version of
	# cabal that we have installed
	cabalpackage=Cabal-$(cabal-version)
	einfo "Using cabal-$(cabal-version)."

	make_setup() {
		set -- -package "${cabalpackage}" --make "${setupmodule}" \
			${GHC_BOOTSTRAP_FLAGS} \
			"$@" \
			-o setup
		echo $(ghc-getghc) ${HCFLAGS} "$@"
		$(ghc-getghc) "$@"
	}
	if $(ghc-supports-shared-libraries); then
		# # some custom build systems might use external libraries,
		# # for which we don't have shared libs, so keep static fallback
		# bug #411789, http://hackage.haskell.org/trac/ghc/ticket/5743#comment:3
		# http://hackage.haskell.org/trac/ghc/ticket/7062
		# http://hackage.haskell.org/trac/ghc/ticket/3072
		# ghc does not set RPATH for extralibs, thus we do it ourselves by hands
		einfo "Prepending $(ghc-libdir) to LD_LIBRARY_PATH"
		if [[ ${CHOST} != *-darwin* ]]; then
			LD_LIBRARY_PATH="$(ghc-libdir)${LD_LIBRARY_PATH:+:}${LD_LIBRARY_PATH}"
			export LD_LIBRARY_PATH
		else
			DYLD_LIBRARY_PATH="$(ghc-libdir)${DYLD_LIBRARY_PATH:+:}${DYLD_LIBRARY_PATH}"
			export DYLD_LIBRARY_PATH
		fi
		{ make_setup -dynamic "$@" && ./setup --help >/dev/null; } ||
		make_setup "$@" || die "compiling ${setupmodule} failed"
	else
		make_setup "$@" || die "compiling ${setupmodule} failed"
	fi
}

cabal-mksetup() {
	local setupdir

	if [[ -n $1 ]]; then
		setupdir=$1
	else
		setupdir=${S}
	fi

	rm -f "${setupdir}"/Setup.{lhs,hs}

	echo 'import Distribution.Simple; main = defaultMainWithHooks defaultUserHooks' \
		> $setupdir/Setup.hs || die "failed to create default Setup.hs"
}

cabal-hscolour() {
	set -- hscolour "$@"
	echo ./setup "$@"
	./setup "$@" || die "setup hscolour failed"
}

cabal-haddock() {
	set -- haddock "$@"
	echo ./setup "$@"
	./setup "$@" || die "setup haddock failed"
}

cabal-hscolour-haddock() {
	# --hyperlink-source implies calling 'setup hscolour'
	set -- haddock --hyperlink-source
	echo ./setup "$@"
	./setup "$@" --hyperlink-source || die "setup haddock --hyperlink-source failed"
}

cabal-configure() {
	has "${EAPI:-0}" 0 1 2 && ! use prefix && EPREFIX=

	if [[ -n "${CABAL_USE_HADDOCK}" ]] && use doc; then
		cabalconf="${cabalconf} --with-haddock=${EPREFIX}/usr/bin/haddock"
	fi
	if [[ -n "${CABAL_USE_PROFILE}" ]] && use profile; then
		cabalconf="${cabalconf} --enable-library-profiling"
	fi
	if [[ -n "${CABAL_USE_ALEX}" ]]; then
		cabalconf="${cabalconf} --with-alex=${EPREFIX}/usr/bin/alex"
	fi

	if [[ -n "${CABAL_USE_HAPPY}" ]]; then
		cabalconf="${cabalconf} --with-happy=${EPREFIX}/usr/bin/happy"
	fi

	if [[ -n "${CABAL_USE_C2HS}" ]]; then
		cabalconf="${cabalconf} --with-c2hs=${EPREFIX}/usr/bin/c2hs"
	fi
	if [[ -n "${CABAL_USE_CPPHS}" ]]; then
		cabalconf="${cabalconf} --with-cpphs=${EPREFIX}/usr/bin/cpphs"
	fi
	if [[ -n "${CABAL_TEST_SUITE}" ]]; then
		cabalconf="${cabalconf} $(use_enable test tests)"
	fi

	local option
	for option in ${HCFLAGS}
	do
		cabalconf+=" --ghc-option=$option"
	done

	# Building GHCi libs on ppc64 causes "TOC overflow".
	if use ppc64; then
		cabalconf="${cabalconf} --disable-library-for-ghci"
	fi

	# currently cabal does not respect CFLAGS and LDFLAGS on it's own (bug #333217)
	# so translate LDFLAGS to ghc parameters (without filtering)
	local flag
	for flag in $LDFLAGS; do cabalconf="${cabalconf} --ghc-option=-optl$flag"; done

	# disable executable stripping for the executables, as portage will
	# strip by itself, and pre-stripping gives a QA warning.
	# cabal versions previous to 1.4 does not strip executables, and does
	# not accept the flag.
	# this fixes numerous bugs, amongst them;
	# bug #251881, bug #251882, bug #251884, bug #251886, bug #299494
	cabalconf="${cabalconf} --disable-executable-stripping"

	cabalconf="${cabalconf} --docdir=${EPREFIX}/usr/share/doc/${PF}"
	# As of Cabal 1.2, configure is quite quiet. For diagnostic purposes
	# it's better if the configure chatter is in the build logs:
	cabalconf="${cabalconf} --verbose"

	# We build shared version of our Cabal where ghc ships it's shared
	# version of it. We will link ./setup as dynamic binary againt Cabal later.
	[[ ${CATEGORY}/${PN} == "dev-haskell/cabal" ]] && \
		$(ghc-supports-shared-libraries) && \
			cabalconf="${cabalconf} --enable-shared"

	if $(ghc-supports-shared-libraries); then
		# maybe a bit lower
		if version_is_at_least "7.7.20121114" "$(ghc-version)"; then
			cabalconf="${cabalconf} --enable-shared"
		fi
	fi

	set -- configure \
		--ghc --prefix="${EPREFIX}"/usr \
		--with-compiler="$(ghc-getghc)" \
		--with-hc-pkg="$(ghc-getghcpkg)" \
		--prefix="${EPREFIX}"/usr \
		--libdir="${EPREFIX}"/usr/$(get_libdir) \
		--libsubdir=${P}/ghc-$(ghc-version) \
		--datadir="${EPREFIX}"/usr/share/ \
		--datasubdir=${P}/ghc-$(ghc-version) \
		${cabalconf} \
		${CABAL_CONFIGURE_FLAGS} \
		${CABAL_EXTRA_CONFIGURE_FLAGS} \
		"$@"
	echo ./setup "$@"
	./setup "$@" || die "setup configure failed"
}

cabal-build() {
	unset LANG LC_ALL LC_MESSAGES
	set --  build ${CABAL_EXTRA_BUILD_FLAGS} "$@"
	echo ./setup "$@"
	./setup "$@" \
		|| die "setup build failed"
}

cabal-copy() {
	has "${EAPI:-0}" 0 1 2 && ! use prefix && ED=${D}

	set -- copy --destdir="${D}" "$@"
	echo ./setup "$@"
	./setup "$@" || die "setup copy failed"

	# cabal is a bit eager about creating dirs,
	# so remove them if they are empty
	rmdir "${ED}/usr/bin" 2> /dev/null
}

cabal-pkg() {
	# This does not actually register since we're using true instead
	# of ghc-pkg. So it just leaves the .conf file and we can
	# register that ourselves (if it exists).

	if [[ -n ${CABAL_HAS_LIBRARIES} ]]; then
		# Newer cabal can generate a package conf for us:
		./setup register --gen-pkg-config="${T}/${P}.conf"
		ghc-setup-pkg "${T}/${P}.conf"
		ghc-install-pkg
	fi
}

# Some cabal libs are bundled along with some versions of ghc
# eg filepath-1.0 comes with ghc-6.6.1
# by putting CABAL_CORE_LIB_GHC_PV="6.6.1" in an ebuild we are declaring that
# when building with this version of ghc, the ebuild is a dummy that is it will
# install no files since the package is already included with ghc.
# However portage still records the dependency and we can upgrade the package
# to a later one that's not included with ghc.
# You can also put a space separated list, eg CABAL_CORE_LIB_GHC_PV="6.6 6.6.1".
cabal-is-dummy-lib() {
	for version in ${CABAL_CORE_LIB_GHC_PV[*]}; do
		[[ "$(ghc-version)" == ${version} ]] && return 0
	done
	return 1
}

# exported function: check if cabal is correctly installed for
# the currently active ghc (we cannot guarantee this with portage)
haskell-cabal_pkg_setup() {
	if [[ -z "${CABAL_HAS_BINARIES}" ]] && [[ -z "${CABAL_HAS_LIBRARIES}" ]]; then
		eqawarn "QA Notice: Neither bin nor lib are in CABAL_FEATURES."
	fi
	if [[ -n "${CABAL_UNKNOWN}" ]]; then
		eqawarn "QA Notice: Unknown entry in CABAL_FEATURES: ${CABAL_UNKNOWN}"
	fi
	if cabal-is-dummy-lib; then
		einfo "${P} is included in ghc-${CABAL_CORE_LIB_GHC_PV}, nothing to install."
	fi
}

haskell-cabal_src_configure() {
	cabal-is-dummy-lib && return

	pushd "${S}" > /dev/null

	cabal-bootstrap

	cabal-configure "$@"

	popd > /dev/null
}

# exported function: nice alias
cabal_src_configure() {
	haskell-cabal_src_configure "$@"
}

# exported function: cabal-style bootstrap configure and compile
cabal_src_compile() {
	# it's a common mistake when one bumps ebuild to EAPI="2" (and upper)
	# and forgets to separate src_compile() to src_configure()/src_compile().
	# Such error leads to default src_configure and we lose all passed flags.
	if ! has "${EAPI:-0}" 0 1; then
		local passed_flag
		for passed_flag in "$@"; do
			[[ ${passed_flag} == --flags=* ]] && \
				eqawarn "QA Notice: Cabal option '${passed_flag}' has effect only in src_configure()"
		done
	fi

	cabal-is-dummy-lib && return

	has src_configure ${HASKELL_CABAL_EXPF} || haskell-cabal_src_configure "$@"
	cabal-build

	if [[ -n "${CABAL_USE_HADDOCK}" ]] && use doc; then
		if [[ -n "${CABAL_USE_HSCOLOUR}" ]] && use hscolour; then
			# hscolour and haddock
			cabal-hscolour-haddock
		else
			# just haddock
			cabal-haddock
		fi
	else
		if [[ -n "${CABAL_USE_HSCOLOUR}" ]] && use hscolour; then
			# just hscolour
			cabal-hscolour
		fi
	fi
}

haskell-cabal_src_compile() {
	pushd "${S}" > /dev/null

	cabal_src_compile "$@"

	popd > /dev/null
}

haskell-cabal_src_test() {
	pushd "${S}" > /dev/null

	if cabal-is-dummy-lib; then
		einfo ">>> No tests for dummy library: ${CATEGORY}/${PF}"
	else
		einfo ">>> Test phase [cabal test]: ${CATEGORY}/${PF}"
		set -- test "$@"
		echo ./setup "$@"
		./setup "$@" || die "cabal test failed"
	fi

	popd > /dev/null
}

# exported function: cabal-style copy and register
cabal_src_install() {
	has "${EAPI:-0}" 0 1 2 && ! use prefix && EPREFIX=

	if ! cabal-is-dummy-lib; then
		cabal-copy
		cabal-pkg
	fi

	# create a dummy local package conf file for haskell-updater
	# if it does not exist (dummy libraries and binaries w/o libraries)
	local ghc_confdir_with_prefix="$(ghc-confdir)"
	# remove EPREFIX
	dodir ${ghc_confdir_with_prefix#${EPREFIX}}
	local conf_file="${D}/$(ghc-confdir)/$(ghc-localpkgconf)"
	[[ -e $conf_file ]] || echo '[]' > "$conf_file" || die

	# make sure installed packages do not destroy ghc's
	# bundled packages
	local initial_pkg_db=${ROOT}/$(ghc-libdir)/package.conf.d.initial
	if [[ -e ${initial_pkg_db} ]]; then
		local checked_pkg
		for checked_pkg in $(ghc-listpkg "${conf_file}")
		do
			local initial_pkg
			for initial_pkg in $(ghc-listpkg "${initial_pkg_db}"); do
				if [[ ${checked_pkg} = ${initial_pkg} ]]; then
					eerror "Package ${checked_pkg} is shipped with $(ghc-version)."
					eerror "Ebuild author forgot CABAL_CORE_LIB_GHC_PV entry."
					eerror "Found in ${initial_pkg_db}."
					die
				fi
			done
		done
	fi
}

haskell-cabal_src_install() {
	pushd "${S}" > /dev/null

	cabal_src_install

	popd > /dev/null
}

# ebuild.sh:use_enable() taken as base
#
# Usage examples:
#
#     CABAL_CONFIGURE_FLAGS=$(cabal_flag gui)
#  leads to "--flags=gui" or "--flags=-gui" (useflag 'gui')
#
#     CABAL_CONFIGURE_FLAGS=$(cabal_flag gtk gui)
#  also leads to "--flags=gui" or " --flags=-gui" (useflag 'gtk')
#
cabal_flag() {
	if [[ -z "$1" ]]; then
		echo "!!! cabal_flag() called without a parameter." >&2
		echo "!!! cabal_flag() <USEFLAG> [<cabal_flagname>]" >&2
		return 1
	fi

	local UWORD=${2:-$1}

	if use "$1"; then
		echo "--flags=${UWORD}"
	else
		echo "--flags=-${UWORD}"
	fi

	return 0
}

# @FUNCTION: cabal_chdeps
# @DESCRIPTION:
# Allows easier patching of $CABAL_FILE (${S}/${PN}.cabal by default)
# depends
#
# Accepts argument list as pairs of substitutions: <from-string> <to-string>...
#
# Dies on error.
#
# Usage examples:
#
# src_prepare() {
#    cabal_chdeps \
#        'base >= 4.2 && < 4.6' 'base >= 4.2 && < 4.7' \
#        'containers ==0.4.*' 'containers >= 0.4 && < 0.6'
#}
# or
# src_prepare() {
#    CABAL_FILE=${S}/${MY_PN}.cabal cabal_chdeps \
#        'base >= 4.2 && < 4.6' 'base >= 4.2 && < 4.7'
#    CABAL_FILE=${S}/${MY_PN}-tools.cabal cabal_chdeps \
#        'base == 3.*' 'base >= 4.2 && < 4.7'
#}
#
cabal_chdeps() {
	local cf=${CABAL_FILE:-${S}/${PN}.cabal}
	local from_ss # ss - substring
	local to_ss
	local orig_c # c - contents
	local new_c

	[[ -f $cf ]] || die "cabal file '$cf' does not exist"

	orig_c=$(< "$cf")

	while :; do
		from_pat=$1
		to_str=$2

		[[ -n ${from_pat} ]] || break
		[[ -n ${to_str} ]] || die "'${from_str}' does not have 'to' part"

		einfo "CHDEP: '${from_pat}' -> '${to_str}'"

		# escape pattern-like symbols
		from_pat=${from_pat//\*/\\*}
		from_pat=${from_pat//\[/\\[}

		new_c=${orig_c//${from_pat}/${to_str}}

		if [[ -n $CABAL_DEBUG_LOOSENING ]]; then
			echo "${orig_c}" >"${T}/${cf}".pre
			echo "${new_c}" >"${T}/${cf}".post
			diff -u "${T}/${cf}".{pre,post}
		fi

		[[ "${orig_c}" == "${new_c}" ]] && die "no trigger for '${from_pat}'"
		orig_c=${new_c}
		shift
		shift
	done

	echo "${new_c}" > "$cf" ||
		die "failed to update"
}