tests/make: extend tests for expression modifiers, especially ':N'

usr.bin/make/unit-tests/varmod-no-match.mk

@@ -1,9 +1,97 @@
-# $NetBSD: varmod-no-match.mk,v 1.2 2020/08/16 14:25:16 rillig Exp $
+# $NetBSD: varmod-no-match.mk,v 1.3 2023/02/26 06:08:06 rillig Exp $
 #
-# Tests for the :N variable modifier, which filters words that do not match
-# the given pattern.
+# Tests for the expression modifier ':N', which filters words that do not
+# match the given pattern.
+
+
+# Keep all words except for 'two'.
+.if ${:U one two three :Ntwo} != "one three"
+.  error
+.endif
+
+# Keep all words except those starting with 't'.
+# See varmod-match.mk for the details of pattern matching.
+.if ${:U one two three four six :Nt*} != "one four six"
+.  error
+.endif
+
+
+# Idiom: normalize whitespace
+#
+# The modifier ':N' can be used with an empty pattern.  As that pattern never
+# matches a word, the only effect is that the string is split into words and
+# then joined again, thereby normalizing whitespace around and between the
+# words.  And even though the 'N' in ':N' might serve as a mnemonic for
+# "normalize whitespace", this idiom is not used in practice, resorting to the
+# much more common ':M*' to "select all words" instead.
+.if ${:U :N} != ""
+.  error
+.endif
+.if ${:U one    two three :N} != "one two three"
+.  error
+.endif
+.if ${:U one    two three :M*} != "one two three"
+.  error
+.endif
+
+
+# Idiom: single-word expression equals any of several words or patterns
+#
+# If an expression is guaranteed to consist of a single word, the modifier
+# ':N' can be chained to compare the expression to several words or even
+# patterns in a sequence.  If one of the patterns matches, the final
+# expression will be the empty string.
+#
+.if ${:U word :None:Ntwo:Nthree} != ""
+#  good
+.else
+.  error
+.endif
+.if ${:U two :None:Ntwo:Nthree} != ""
+.  error
+.else
+#  good
+.endif
+#
+# The modifier ':N' is seldom used in general since positive matches with ':M'
+# are easier to grasp.  Chaining the ':N' modifier is even more difficult to
+# grasp due to the many negations involved.
+#
+# The final '!= ""' adds to the confusion because at first glance, the
+# condition may look like '${VAR} != ""', which for a single-word variable is
+# always true.
+#
+# The '!= ""' can be omitted if the expression cannot have the numeric value
+# 0, which is common in practice.  In that form, each ':N' can be pronounced
+# as 'neither' or 'nor', which makes the expression sound more natural.
+#
+.if ${:U word :None:Ntwo:Nthree}
+#  good
+.else
+.  error
+.endif
+.if ${:U two :None:Ntwo:Nthree}
+.  error
+.else
+#  good
+.endif
+#
+# Replacing the '${...} != ""' with '!empty(...)' doesn't improve the
+# situation as the '!' adds another level of negations, and the word 'empty'
+# is a negation on its own, thereby creating a triple negation.  Furthermore,
+# due to the '!empty', the expression to be evaluated no longer starts with
+# '$' and is thus more difficult to spot quickly.
+#
+.if !empty(:U word :None:Ntwo:Nthree)
+#  good
+.else
+.  error
+.endif
+.if !empty(:U two :None:Ntwo:Nthree)
+.  error
+.else
+#  good
+.endif
 
-# TODO: Implementation
 
 all:
-	@:;

usr.bin/make/unit-tests/varmod-order-shuffle.mk

@@ -1,13 +1,14 @@
-# $NetBSD: varmod-order-shuffle.mk,v 1.7 2021/08/03 04:46:49 rillig Exp $
+# $NetBSD: varmod-order-shuffle.mk,v 1.8 2023/02/26 06:08:06 rillig Exp $
 #
 # Tests for the :Ox variable modifier, which returns the words of the
 # variable, shuffled.
 #
 # The variable modifier :Ox is available since 2005-06-01.
 #
 # As of 2020-08-16, make uses random(3) seeded by the current time in seconds.
-# This makes the random numbers completely predictable since there is no other
-# part of make that uses random numbers.
+# This makes the random numbers completely predictable since the only other
+# part of make that uses random numbers is the 'randomize-targets' mode, which
+# is off by default.
 #
 # Tags: probabilistic
 

usr.bin/make/unit-tests/varmod-order.exp

@@ -19,6 +19,8 @@ make: Bad modifier ":Onrr" for variable "NUMBERS"
 make: "varmod-order.mk" line 77: Malformed conditional (${NUMBERS:Onrr})
 make: Bad modifier ":Orrn" for variable "NUMBERS"
 make: "varmod-order.mk" line 86: Malformed conditional (${NUMBERS:Orrn})
+make: Bad modifier ":On=Off" for variable "SWITCH"
+make: "varmod-order.mk" line 96: Malformed conditional (${SWITCH:UOn:On=Off} != "Off")
 make: Fatal errors encountered -- cannot continue
 make: stopped in unit-tests
 exit status 1

usr.bin/make/unit-tests/varmod-order.mk

@@ -1,4 +1,4 @@
-# $NetBSD: varmod-order.mk,v 1.8 2022/01/15 12:35:18 rillig Exp $
+# $NetBSD: varmod-order.mk,v 1.9 2023/02/26 06:08:06 rillig Exp $
 #
 # Tests for the :O variable modifier and its variants, which either sort the
 # words of the value or shuffle them.
@@ -89,4 +89,14 @@ _:=	${NUMBERS:Onr
 .  error
 .endif
 
+
+# Any modifier that starts with 'O' either sorts or shuffles the words.  Other
+# than for many other modifiers, there is no fallback to the SysV modifier
+# ':from=to'.
+.if ${SWITCH:UOn:On=Off} != "Off"
+.  error
+.else
+.  error
+.endif
+
 all: