Added ifthen() policy function

examples/ifthen.cf

@@ -0,0 +1,42 @@
+#  Copyright 2026 Northern.tech AS
+#  This file is part of CFEngine 3 - written and maintained by Northern.tech AS.
+#  This program is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU General Public License as published by the
+#  Free Software Foundation; version 3.
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA
+# To the extent this program is licensed as part of the Enterprise
+# versions of Cfengine, the applicable Commercial Open Source License
+# (COSL) may apply to this file if you as a licensee so wish it. See
+# included file COSL.txt.
+#+begin_src cfengine3
+bundle agent __main__
+{
+  classes:
+    "webserver" expression => "any";
+
+  vars:
+    # The value of the first true class expression is used.
+    "port" string => ifthen("dbserver", "5432", "webserver", "80");
+
+    # No class expression is true, so the variable is not defined.
+    "unset" string => ifthen("dbserver", "5432", "mailserver", "25");
+
+  reports:
+    "port is $(port)";
+    "unset is not defined" if => not(isvariable("unset"));
+}
+
+#+end_src
+###############################################################################
+#+begin_src example_output
+#@ ```
+#@ R: port is 80
+#@ R: unset is not defined
+#@ ```
+#+end_src

libpromises/evalfunction.c

@@ -1872,6 +1872,44 @@ static FnCallResult FnCallIfElse(EvalContext *ctx,
 
 /*********************************************************************/
 
+static FnCallResult FnCallIfThen(EvalContext *ctx,
+                                 ARG_UNUSED const Policy *policy,
+                                 const FnCall *fp,
+                                 const Rlist *finalargs)
+{
+    assert(fp != NULL);
+
+    /* We need to check all the arguments, ArgTemplate does not check varadic functions */
+    for (const Rlist *arg = finalargs; arg != NULL; arg = arg->next)
+    {
+        SyntaxTypeMatch err = CheckConstraintTypeMatch(fp->name, arg->val, CF_DATA_TYPE_STRING, "", 1);
+        if (err != SYNTAX_TYPE_MATCH_OK && err != SYNTAX_TYPE_MATCH_ERROR_UNEXPANDED)
+        {
+            FatalError(ctx, "Function '%s', %s", fp->name, SyntaxTypeMatchToString(err));
+        }
+    }
+
+    /* Unlike ifelse(), there is no fall-through value. */
+    const size_t argcount = RlistLen(finalargs);
+    if ((argcount == 0) || ((argcount % 2) != 0))
+    {
+        FatalError(ctx, "Function '%s' requires pairs of class expressions and values", fp->name);
+    }
+
+    for (const Rlist *arg = finalargs; arg != NULL; arg = arg->next->next)
+    {
+        if (IsDefinedClass(ctx, RlistScalarValue(arg)))
+        {
+            return FnReturn(RlistScalarValue(arg->next));
+        }
+    }
+
+    /* None is true, leave the variable undefined. */
+    return FnFailure();
+}
+
+/*********************************************************************/
+
 static FnCallResult FnCallClassesMatching(EvalContext *ctx, ARG_UNUSED const Policy *policy, const FnCall *fp, const Rlist *finalargs)
 {
     assert(finalargs != NULL);
@@ -11071,6 +11109,13 @@ static const FnCallArg IFELSE_ARGS[] =
     {NULL, CF_DATA_TYPE_NONE, NULL}
 };
 
+static const FnCallArg IFTHEN_ARGS[] =
+{
+    {CF_ANYSTRING, CF_DATA_TYPE_STRING, "Class expression"},
+    {CF_ANYSTRING, CF_DATA_TYPE_STRING, "Value if the preceding class expression is true"},
+    {NULL, CF_DATA_TYPE_NONE, NULL}
+};
+
 static const FnCallArg INT_ARGS[] =
 {
     {CF_ANYSTRING, CF_DATA_TYPE_STRING, "Numeric string to convert to integer"},
@@ -11981,6 +12026,8 @@ const FnCallType CF_FNCALL_TYPES[] =
                   FNCALL_OPTION_CACHED, FNCALL_CATEGORY_COMM, SYNTAX_STATUS_NORMAL, DEFAULT_ARGC),
     FnCallTypeNew("ifelse", CF_DATA_TYPE_STRING, IFELSE_ARGS, &FnCallIfElse, "Do If-ElseIf-ElseIf-...-Else evaluation of arguments",
                   FNCALL_OPTION_VARARG, FNCALL_CATEGORY_DATA, SYNTAX_STATUS_NORMAL, ARGC(1, -1)),
+    FnCallTypeNew("ifthen", CF_DATA_TYPE_STRING, IFTHEN_ARGS, &FnCallIfThen, "Return the value of the first true class expression, or nothing if none is true",
+                  FNCALL_OPTION_VARARG, FNCALL_CATEGORY_DATA, SYNTAX_STATUS_NORMAL, ARGC(2, -1)),
     FnCallTypeNew("int", CF_DATA_TYPE_INT, INT_ARGS, &FnCallInt, "Convert numeric string to int",
                   FNCALL_OPTION_NONE, FNCALL_CATEGORY_DATA, SYNTAX_STATUS_NORMAL, DEFAULT_ARGC),
     FnCallTypeNew("intersection", CF_DATA_TYPE_STRING_LIST, SETOP_ARGS, &FnCallSetop, "Returns all the unique elements of list or array or data container arg1 that are also in list or array or data container arg2",

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

@@ -0,0 +1,54 @@
+######################################################
+#
+# Test that ifthen() behaves as expected
+#
+#####################################################
+body common control
+{
+  inputs => { "../../default.sub.cf" };
+  bundlesequence => { default("$(this.promise_filename)") };
+  version => "1.0";
+}
+
+#######################################################
+bundle agent test
+{
+  meta:
+    "description" -> { "ENT-14719" }
+      string => "Test that ifthen() returns the value of the first true class expression and leaves the variable undefined if none is true";
+
+  vars:
+    "single" string => ifthen("any", "single value");
+    "first" string => ifthen("!any", "wrong", "any", "first", "any", "second");
+    "nested" string => ifthen(not("!any"), "nested");
+    "expanded_var" string => "expanded";
+    "expanded" string => ifthen("any", "$(expanded_var)");
+    "none" string => ifthen("!any", "wrong");
+
+    # Unlike 3-argument ifelse(), not evaluated while an argument has an
+    # unresolved variable, even if an earlier pair is true.
+    "unresolved"
+      string => ifthen("any", "value", "any", "$(no_such_bundle.no_such_var)");
+}
+
+#######################################################
+bundle agent check
+{
+  classes:
+    "ok"
+      and => {
+        strcmp("$(test.single)", "single value"),
+        strcmp("$(test.first)", "first"),
+        strcmp("$(test.nested)", "nested"),
+        strcmp("$(test.expanded)", "expanded"),
+        not(isvariable("test.none")),
+        not(isvariable("test.unresolved")),
+      };
+
+  reports:
+    ok::
+      "$(this.promise_filename) Pass";
+
+    !ok::
+      "$(this.promise_filename) FAIL";
+}

tests/acceptance/01_vars/02_functions/ifthen_no_args.x.cf

@@ -0,0 +1,29 @@
+######################################################
+#
+# Test that ifthen() with no arguments is an error
+#
+#####################################################
+body common control
+{
+  inputs => { "../../default.sub.cf" };
+  bundlesequence => { default("$(this.promise_filename)") };
+  version => "1.0";
+}
+
+#######################################################
+bundle agent test
+{
+  meta:
+    "description" -> { "ENT-14719" }
+      string => "Test that ifthen() with no arguments is an error";
+
+  vars:
+    "x" string => ifthen();
+}
+
+#######################################################
+bundle agent check
+{
+  reports:
+    "$(this.promise_filename) FAIL";
+}

tests/acceptance/01_vars/02_functions/ifthen_odd_args.x.cf

@@ -0,0 +1,29 @@
+######################################################
+#
+# Test that ifthen() with an odd number of arguments is an error
+#
+#####################################################
+body common control
+{
+  inputs => { "../../default.sub.cf" };
+  bundlesequence => { default("$(this.promise_filename)") };
+  version => "1.0";
+}
+
+#######################################################
+bundle agent test
+{
+  meta:
+    "description" -> { "ENT-14719" }
+      string => "Test that ifthen() with an odd number of arguments is an error";
+
+  vars:
+    "x" string => ifthen("any", "value", "fallthrough");
+}
+
+#######################################################
+bundle agent check
+{
+  reports:
+    "$(this.promise_filename) FAIL";
+}