[src/trunk]: src/usr.bin/make/unit-tests make(1): add tests and tutorial for ...

[rillig <rillig%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/d731a468b2b2
branches:  trunk
changeset: 946760:d731a468b2b2
user:      rillig <rillig%NetBSD.org@localhost>
date:      Mon Dec 07 21:35:43 2020 +0000

description:
make(1): add tests and tutorial for the ?= assignment operator

diffstat:

 distrib/sets/lists/tests/mi               |   6 +-
 usr.bin/make/unit-tests/Makefile          |   3 +-
 usr.bin/make/unit-tests/qequals.exp       |   2 -
 usr.bin/make/unit-tests/qequals.mk        |   8 ---
 usr.bin/make/unit-tests/var-op-default.mk |  72 ++++++++++++++++++++++++++++++-
 5 files changed, 74 insertions(+), 17 deletions(-)

diffs (138 lines):

diff -r ba3ba8dab220 -r d731a468b2b2 distrib/sets/lists/tests/mi
--- a/distrib/sets/lists/tests/mi       Mon Dec 07 20:28:53 2020 +0000
+++ b/distrib/sets/lists/tests/mi       Mon Dec 07 21:35:43 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: mi,v 1.984 2020/12/07 07:51:25 rillig Exp $
+# $NetBSD: mi,v 1.985 2020/12/07 21:35:43 rillig Exp $
 #
 # Note: don't delete entries from here - mark them as "obsolete" instead.
 #
@@ -5263,8 +5263,8 @@
 ./usr/tests/usr.bin/make/unit-tests/posix.mk                                   tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/make/unit-tests/posix1.exp                                 tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/make/unit-tests/posix1.mk                                  tests-usr.bin-tests     compattestfile,atf
-./usr/tests/usr.bin/make/unit-tests/qequals.exp                                        tests-usr.bin-tests     compattestfile,atf
-./usr/tests/usr.bin/make/unit-tests/qequals.mk                                 tests-usr.bin-tests     compattestfile,atf
+./usr/tests/usr.bin/make/unit-tests/qequals.exp                                        tests-obsolete          obsolete,atf
+./usr/tests/usr.bin/make/unit-tests/qequals.mk                                 tests-obsolete          obsolete,atf
 ./usr/tests/usr.bin/make/unit-tests/recursive.exp                              tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/make/unit-tests/recursive.mk                               tests-usr.bin-tests     compattestfile,atf
 ./usr/tests/usr.bin/make/unit-tests/sh-dots.exp                                        tests-usr.bin-tests     compattestfile,atf
diff -r ba3ba8dab220 -r d731a468b2b2 usr.bin/make/unit-tests/Makefile
--- a/usr.bin/make/unit-tests/Makefile  Mon Dec 07 20:28:53 2020 +0000
+++ b/usr.bin/make/unit-tests/Makefile  Mon Dec 07 21:35:43 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.238 2020/12/07 01:32:04 rillig Exp $
+# $NetBSD: Makefile,v 1.239 2020/12/07 21:35:43 rillig Exp $
 #
 # Unit tests for make(1)
 #
@@ -257,7 +257,6 @@
 TESTS+=                phony-end
 TESTS+=                posix
 TESTS+=                # posix1        # broken by reverting POSIX changes
-TESTS+=                qequals
 TESTS+=                recursive
 TESTS+=                sh
 TESTS+=                sh-dots
diff -r ba3ba8dab220 -r d731a468b2b2 usr.bin/make/unit-tests/qequals.exp
--- a/usr.bin/make/unit-tests/qequals.exp       Mon Dec 07 20:28:53 2020 +0000
+++ /dev/null   Thu Jan 01 00:00:00 1970 +0000
@@ -1,2 +0,0 @@
-V.i386 ?= OK
-exit status 0
diff -r ba3ba8dab220 -r d731a468b2b2 usr.bin/make/unit-tests/qequals.mk
--- a/usr.bin/make/unit-tests/qequals.mk        Mon Dec 07 20:28:53 2020 +0000
+++ /dev/null   Thu Jan 01 00:00:00 1970 +0000
@@ -1,8 +0,0 @@
-# $NetBSD: qequals.mk,v 1.3 2020/10/24 08:50:17 rillig Exp $
-
-M=     i386
-V.i386=        OK
-V.$M?= bug
-
-all:
-       @echo 'V.$M ?= ${V.$M}'
diff -r ba3ba8dab220 -r d731a468b2b2 usr.bin/make/unit-tests/var-op-default.mk
--- a/usr.bin/make/unit-tests/var-op-default.mk Mon Dec 07 20:28:53 2020 +0000
+++ b/usr.bin/make/unit-tests/var-op-default.mk Mon Dec 07 21:35:43 2020 +0000
@@ -1,9 +1,77 @@
-# $NetBSD: var-op-default.mk,v 1.2 2020/08/16 14:25:16 rillig Exp $
+# $NetBSD: var-op-default.mk,v 1.3 2020/12/07 21:35:43 rillig Exp $
 #
 # Tests for the ?= variable assignment operator, which only assigns
 # if the variable is still undefined.
 
-# TODO: Implementation
+# The variable VAR is not defined yet.  Therefore it gets the default value
+# from the variable assignment.
+VAR?=          default value
+.if ${VAR} != "default value"
+.  error
+.endif
+
+# At this point, the variable 'VAR' is already defined.  The '?=' therefore
+# ignores the new variable value, preserving the previous "default value".
+VAR?=          ignored
+.if ${VAR} != "default value"
+.  error
+.endif
+
+# The '?=' operator only checks whether the variable is defined or not.
+# An empty variable is defined, therefore the '?=' operator does nothing.
+EMPTY=         # empty
+EMPTY?=                ignored
+.if ${EMPTY} != ""
+.  error
+.endif
+
+# The .for loop is described in the manual page as if it would operate on
+# variables.  This is not entirely true.  Instead, each occurrence of an
+# expression $i or ${i} or ${i:...} is substituted with ${:Uloop-value}.
+# This comes very close to the description, the only difference is that
+# there is never an actual variable named 'i' involved.
+#
+# Because there is not really a variable named 'i', the '?=' operator
+# performs the variable assignment, resulting in $i == "default".
+.for i in loop-value
+i?=            default
+.endfor
+.if ${i} != "default"
+.  error
+.endif
+
+# At the point where the '?=' operator checks whether the variable exists,
+# it expands the variable name exactly once.  Therefore both 'VAR.param'
+# and 'VAR.${param}' expand to 'VAR.param', and the second '?=' assignment
+# has no effect.
+#
+# Since 2000.05.11.07.43.42 it has been possible to use nested variable
+# expressions in variable names, which made make much more versatile.
+# On 2008.03.31.00.12.21, this particular case of the '?=' operator has been
+# fixed.  Before, the '?=' operator had not expanded the variable name
+# 'VAR.${:Uparam}' to see whether the variable already existed.  Since that
+# variable didn't exist (and variables with '$' in their name are particularly
+# fragile), the variable assignment with "not used" was performed, and only
+# during that, the variable name was expanded.
+VAR.param=             already defined
+VAR.${:Uparam}?=       not used
+.if ${VAR.param} != "already defined"
+.  error
+.endif
+
+# Now demonstrate that the variable name is indeed expanded exactly once.
+# This is tricky to measure correctly since there are many inconsistencies
+# in and around the code that expands variable expressions in the various
+# places where variable expressions can occur.  If in doubt, enable the
+# following debug flags to see what happens:
+#.MAKEFLAGS: -dcpv
+EXPAND_NAME=           EXPAND.$$$$     # The full variable name is EXPAND.$$
+PARAM=                 $$$$
+EXPAND.${PARAM}?=      value with param
+.if ${${EXPAND_NAME}} != "value with param"
+.  error
+.endif
+.MAKEFLAGS: -d0
 
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