Make expandrange able to output a single value

- Allow ranges with a unique value (as the range is already inclusive)
- Make invalid step value a soft fail

Changelog: Allow expandrange to output a single value

Author: amousset

libpromises/evalfunction.c

@@ -4558,9 +4558,10 @@ static FnCallResult FnCallExpandRange(EvalContext *ctx, ARG_UNUSED const Policy
         sscanf(template, "%[^[\[][%d-%d]%[^\n]", before, &from, &to, after);
     }
 
-    if (step_size < 1 || abs(from-to) < step_size)
+    if (step_size < 1)
     {
-        FatalError(ctx, "EXPANDRANGE Step size cannot be less than 1 or greater than the interval");
+        Log(LOG_LEVEL_ERR, "%s: Step size cannot be less than 1", fp->name);
+        return FnFailure();
     }
 
     if (from == CF_NOINT || to == CF_NOINT)

tests/acceptance/01_vars/02_functions/expand_range.cf

@@ -0,0 +1,43 @@
+# data_regextract() test
+
+body common control
+{
+      inputs => { "../../default.cf.sub" };
+      bundlesequence => { default("$(this.promise_filename)") };
+}
+
+bundle agent test
+{
+  vars:
+    "case1"  slist  => expandrange("case1[1-3]", 1);
+    "case1s" string => format("%S", "case1");
+    "case2"  slist  => expandrange("case2[1-10]", 3);
+    "case2s" string => format("%S", "case2");
+    "case3"  slist  => expandrange("case3[1-1]", 3);
+    "case3s" string => format("%S", "case3");
+    "case4"  slist  => expandrange("case4[1-2]", 3);
+    "case4s" string => format("%S", "case4");
+}
+
+bundle agent check
+{
+  vars:
+      "actual" string => "
+1 $(test.case1s)
+2 $(test.case2s)
+3 $(test.case3s)
+4 $(test.case4s)
+";
+
+      "expected" string => '
+1 { \"case11\", \"case12\", \"case13\" }
+2 { \"case21\", \"case24\", \"case27\", \"case210\" }
+3 { \"case31\" }
+4 { \"case41\" }
+';
+
+  methods:
+      "" usebundle => dcs_check_strcmp($(actual), $(expected),
+                                      $(this.promise_filename),
+                                      "no");
+}