Added the function name to the result cache key

The function cache only used the args values, which in some cases could
lead to mixing results from different functions with the same arguments.

Ticket: CFE-4244
Changelog: Cashed policy function results now take into account number of arguments and function name.
Signed-off-by: Lars Erik Wik <lars.erik.wik@northern.tech>
Co-authored-by: Alexis Mousset <alexis.mousset@rudder.io>

libpromises/eval_context.c

@@ -2837,7 +2837,14 @@ bool EvalContextFunctionCacheGet(const EvalContext *ctx,
         return false;
     }
 
-    Rval *rval = FuncCacheMapGet(ctx->function_cache, args);
+    // The cache key is made of the function name and all args values
+    Rlist *args_copy = RlistCopy(args);
+    assert(fp != NULL);
+    assert(fp->name != NULL);
+    assert(ctx != NULL);
+    Rlist *key = RlistPrepend(&args_copy, fp->name, RVAL_TYPE_SCALAR);
+    Rval *rval = FuncCacheMapGet(ctx->function_cache, key);
+    RlistDestroy(key);
     if (rval)
     {
         if (rval_out)
@@ -2863,7 +2870,14 @@ void EvalContextFunctionCachePut(EvalContext *ctx,
 
     Rval *rval_copy = xmalloc(sizeof(Rval));
     *rval_copy = RvalCopy(*rval);
-    FuncCacheMapInsert(ctx->function_cache, RlistCopy(args), rval_copy);
+
+    Rlist *args_copy = RlistCopy(args);
+    assert(fp != NULL);
+    assert(fp->name != NULL);
+    assert(ctx != NULL);
+    Rlist *key = RlistPrepend(&args_copy, fp->name, RVAL_TYPE_SCALAR);
+
+    FuncCacheMapInsert(ctx->function_cache, key, rval_copy);
 }
 
 /* cfPS and associated machinery */

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

@@ -0,0 +1,51 @@
+#######################################################
+#
+# Test that the function result cache checks function name
+#
+#######################################################
+
+body common control
+{
+      inputs => { "../../default.cf.sub" };
+      bundlesequence  => { default("$(this.promise_filename)") };
+      version => "1.0";
+}
+
+#######################################################
+
+
+bundle agent init
+{
+  vars:
+      "agent_regex" string => ".*cf-agent.*";
+}
+
+#######################################################
+
+bundle common test
+{
+  meta:
+    "description" -> { "CFE-4244" }
+      string => "Test that the function result cache checks function name";
+
+  vars:
+      "res1" data => findprocesses("${init.agent_regex}");
+
+  classes:
+      # must not reuse result from previous line
+      # is reused, produces a type error
+      "_pass" expression => processexists("${init.agent_regex}");
+}
+
+
+#######################################################
+
+bundle agent check
+{
+  methods:
+    _pass:: 
+      "pass" usebundle => dcs_pass("$(this.promise_filename)");
+
+    !_pass::
+      "pass" usebundle => dcs_fail("$(this.promise_filename)");
+}