1 files changed, 127 insertions, 0 deletions
diff --git a/unit-tests/varmod-loop-varname.mk b/unit-tests/varmod-loop-varname.mk
new file mode 100644
index 000000000000..d51e2ba76a42
--- /dev/null
+++ b/unit-tests/varmod-loop-varname.mk
@@ -0,0 +1,127 @@
+# $NetBSD: varmod-loop-varname.mk,v 1.2 2021/04/04 13:35:26 rillig Exp $
+#
+# Tests for the first part of the variable modifier ':@var@...@', which
+# contains the variable name to use during the loop.
+
+.MAKE.SAVE_DOLLARS=	yes
+
+
+# Before 2021-04-04, the name of the loop variable could be generated
+# dynamically.  There was no practical use-case for this.
+# Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
+# variable name.
+.if ${:Uone two three:@${:Ubar:S,b,v,}@+${var}+@} != "+one+ +two+ +three+"
+.  error
+.endif
+
+
+# ":::" is a very creative variable name, unlikely to occur in practice.
+# The expression ${\:\:\:} would not work since backslashes can only
+# be escaped in the modifiers, but not in the variable name, therefore
+# the extra indirection via the modifier ':U'.
+.if ${:U1 2 3:@:::@x${${:U\:\:\:}}y@} != "x1y x2y x3y"
+.  error
+.endif
+
+
+# "@@" is another creative variable name.
+.if ${:U1 2 3:@\@\@@x${@@}y@} != "x1y x2y x3y"
+.  error
+.endif
+
+
+# In extreme cases, even the backslash can be used as variable name.
+# It needs to be doubled though.
+.if ${:U1 2 3:@\\@x${${:Ux:S,x,\\,}}y@} != "x1y x2y x3y"
+.  error
+.endif
+
+
+# The variable name can technically be empty, and in this situation
+# the variable value cannot be accessed since the empty "variable"
+# is protected to always return an empty string.
+.if ${:U1 2 3:@@x${}y@} != "xy xy xy"
+.  error
+.endif
+
+
+# The :@ modifier resolves the variables from the replacement text once more
+# than expected.  In particular, it resolves _all_ variables from the scope,
+# and not only the loop variable (in this case v).
+SRCS=		source
+CFLAGS.source=	before
+ALL_CFLAGS:=	${SRCS:@src@${CFLAGS.${src}}@}	# note the ':='
+CFLAGS.source+=	after
+.if ${ALL_CFLAGS} != "before"
+.  error
+.endif
+
+
+# In the following example, the modifier ':@' expands the '$$' to '$'.  This
+# means that when the resulting expression is evaluated, these resulting '$'
+# will be interpreted as starting a subexpression.
+#
+# The d means direct reference, the i means indirect reference.
+RESOLVE=	${RES1} $${RES1}
+RES1=		1d${RES2} 1i$${RES2}
+RES2=		2d${RES3} 2i$${RES3}
+RES3=		3
+
+.if ${RESOLVE:@v@w${v}w@} != "w1d2d3w w2i3w w1i2d3 2i\${RES3}w w1d2d3 2i\${RES3} 1i\${RES2}w"
+.  error
+.endif
+
+
+# Until 2020-07-20, the variable name of the :@ modifier could end with one
+# or two dollar signs, which were silently ignored.
+# There's no point in allowing a dollar sign in that position.
+# Since var.c 1.907 from 2021-04-04, a '$' is no longer allowed in the
+# variable name.
+.if ${1 2 3:L:@v$@($v)@} != "(1) (2) (3)"
+.  error
+.else
+.  error
+.endif
+.if ${1 2 3:L:@v$$@($v)@} != "() () ()"
+.  error
+.else
+.  error
+.endif
+.if ${1 2 3:L:@v$$$@($v)@} != "() () ()"
+.  error
+.else
+.  error
+.endif
+
+
+# It may happen that there are nested :@ modifiers that use the same name for
+# for the loop variable.  These modifiers influence each other.
+#
+# As of 2020-10-18, the :@ modifier is implemented by actually setting a
+# variable in the scope of the expression and deleting it again after the
+# loop.  This is different from the .for loops, which substitute the variable
+# expression with ${:Uvalue}, leading to different unwanted side effects.
+#
+# To make the behavior more predictable, the :@ modifier should restore the
+# loop variable to the value it had before the loop.  This would result in
+# the string "1a b c1 2a b c2 3a b c3", making the two loops independent.
+.if ${:U1 2 3:@i@$i${:Ua b c:@i@$i@}${i:Uu}@} != "1a b cu 2a b cu 3a b cu"
+.  error
+.endif
+
+# During the loop, the variable is actually defined and nonempty.
+# If the loop were implemented in the same way as the .for loop, the variable
+# would be neither defined nor nonempty since all expressions of the form
+# ${var} would have been replaced with ${:Uword} before evaluating them.
+.if defined(var)
+.  error
+.endif
+.if ${:Uword:@var@${defined(var):?def:undef} ${empty(var):?empty:nonempty}@} \
+    != "def nonempty"
+.  error
+.endif
+.if defined(var)
+.  error
+.endif
+
+all: .PHONY