1 files changed, 53 insertions, 1 deletions
diff --git a/unit-tests/varmod-ifelse.mk b/unit-tests/varmod-ifelse.mk
index e8e92b35d1c1..8bd67195282c 100644
--- a/unit-tests/varmod-ifelse.mk
+++ b/unit-tests/varmod-ifelse.mk
@@ -1,9 +1,61 @@
-# $NetBSD: varmod-ifelse.mk,v 1.2 2020/08/16 14:25:16 rillig Exp $
+# $NetBSD: varmod-ifelse.mk,v 1.5 2020/10/23 14:24:51 rillig Exp $
 #
 # Tests for the ${cond:?then:else} variable modifier, which evaluates either
 # the then-expression or the else-expression, depending on the condition.
+#
+# The modifier was added on 1998-04-01.
+#
+# Until 2015-10-11, the modifier always evaluated both the "then" and the
+# "else" expressions.
 
 # TODO: Implementation
 
+# The variable name of the expression is expanded and then taken as the
+# condition.  In this case it becomes:
+#
+#	variable expression == "variable expression"
+#
+# This confuses the parser, which expects an operator instead of the bare
+# word "expression".  If the name were expanded lazily, everything would be
+# fine since the condition would be:
+#
+#	${:Uvariable expression} == "literal"
+#
+# Evaluating the variable name lazily would require additional code in
+# Var_Parse and ParseVarname, it would be more useful and predictable
+# though.
+.if ${${:Uvariable expression} == "literal":?bad:bad}
+.  error
+.else
+.  error
+.endif
+
+# In a variable assignment, undefined variables are not an error.
+# Because of the early expansion, the whole condition evaluates to
+# ' == ""' though, which cannot be parsed because the left-hand side looks
+# empty.
+COND:=	${${UNDEF} == "":?bad-assign:bad-assign}
+
+# In a condition, undefined variables generate a "Malformed conditional"
+# error.  That error message is wrong though.  In lint mode, the correct
+# "Undefined variable" error message is generated.
+# The difference to the ':=' variable assignment is the additional
+# "Malformed conditional" error message.
+.if ${${UNDEF} == "":?bad-cond:bad-cond}
+.  error
+.else
+.  error
+.endif
+
+# When the :? is parsed, it is greedy.  The else branch spans all the
+# text, up until the closing character '}', even if the text looks like
+# another modifier.
+.if ${1:?then:else:Q} != "then"
+.  error
+.endif
+.if ${0:?then:else:Q} != "else:Q"
+.  error
+.endif
+
 all:
 	@:;