tests/make: replace or document .error in tests

The text 'Missing argument for ".error"' in an .exp file may be a hint
for an accidentally broken test, so eliminate them as far as possible.

usr.bin/make/unit-tests/directive-for-empty.exp

@@ -1,7 +1,4 @@
 make: "directive-for-empty.mk" line 22: 2
-make: "directive-for-empty.mk" line 38: Missing argument for ".error"
-make: "directive-for-empty.mk" line 38: Missing argument for ".error"
-make: "directive-for-empty.mk" line 38: Missing argument for ".error"
 For: end for 1
 For: loop body with i = value:
 # The identifier 'empty' can only be used in conditions such as .if, .ifdef or
@@ -22,6 +19,4 @@ CPPFLAGS+=	-Dmessage="empty(i)"
 # condition directives, they can also occur in the modifier ':?', see
 # varmod-ifelse.mk.
 CPPFLAGS+=	-Dmacro="${empty(i):?empty:not-empty}"
-make: Fatal errors encountered -- cannot continue
+exit status 0
-make: stopped in unit-tests
-exit status 1

usr.bin/make/unit-tests/directive-for-empty.mk

@@ -1,4 +1,4 @@
-# $NetBSD: directive-for-empty.mk,v 1.3 2023/11/19 21:47:52 rillig Exp $
+# $NetBSD: directive-for-empty.mk,v 1.4 2024/05/31 07:13:12 rillig Exp $
 #
 # Tests for .for loops containing conditions of the form 'empty(var:...)'.
 #
@@ -26,23 +26,23 @@
 
 # In conditions, the function call to 'empty' does not look like an
 # expression, therefore it is not replaced.  Since there is no global variable
-# named 'i', this expression makes for a leaky abstraction.  If the .for
+# named 'i', this condition makes for a leaky abstraction.  If the .for
 # variables were real variables, calling 'empty' would work on them as well.
 .for i in 11 12 13
 # Asking for an empty iteration variable does not make sense as the .for loop
 # splits the iteration items into words, and such a word cannot be empty.
-.  if empty(i)
+.  if !empty(i)
-# expect+3: Missing argument for ".error"
+.    error			# not reached, due to the leaky abstraction
-# expect+2: Missing argument for ".error"
-# expect+1: Missing argument for ".error"
-.    error			# due to the leaky abstraction
 .  endif
-# The typical way of using 'empty' with variables from .for loops is pattern
+# The typical way of mistakenly using 'empty' with variables from .for loops
-# matching using the modifiers ':M' or ':N'.
+# is pattern matching using the modifiers ':M' or ':N'.
 .  if !empty(i:M*2*)
-.    if ${i} != "12"
+.    error
-.      error
+.  endif
-.    endif
+# Instead of the 'empty' function, the variables from .for loops can be
+# queried using conditions of the form '${var:...} != ""'.
+.  if $i == "12" && ${i:M*2*} != "12"
+.    error
 .  endif
 .endfor
 
@@ -122,3 +122,5 @@ CPPFLAGS+=	-Dmacro="${empty(i):?empty:not-empty}"
 
 # TODO: Add code that demonstrates the current interaction between variables
 #  from .for loops and the modifiers mentioned above.
+
+all:

usr.bin/make/unit-tests/opt-debug-hash.exp

@@ -1,4 +1,4 @@
-make: "opt-debug-hash.mk" line 12: Missing argument for ".error"
+make: "opt-debug-hash.mk" line 13: Missing argument for ".error"
 make: Fatal errors encountered -- cannot continue
 HashTable targets: size=16 numEntries=0 maxchain=0
 HashTable Global variables: size=16 numEntries=<entries> maxchain=3

usr.bin/make/unit-tests/opt-debug-hash.mk

@@ -1,4 +1,4 @@
-# $NetBSD: opt-debug-hash.mk,v 1.4 2023/06/01 20:56:35 rillig Exp $
+# $NetBSD: opt-debug-hash.mk,v 1.5 2024/05/31 07:13:12 rillig Exp $
 #
 # Tests for the -dh command line option, which adds debug logging for
 # hash tables.  Even more detailed logging is available by compiling
@@ -6,7 +6,8 @@
 
 .MAKEFLAGS: -dh
 
-# Force a parse error, to demonstrate the newline character in the diagnostic
+# Force a parse error, to demonstrate the newline character in the "cannot
-# that had been missing before parse.c 1.655 from 2022-01-22.
+# continue" diagnostic that had been missing before parse.c 1.655 from
+# 2022-01-22.
 # expect+1: Missing argument for ".error"
 .error