feat: add rule engine function float2str/2

apps/emqx_plugin_libs/src/emqx_plugin_libs_rule.erl

@@ -39,6 +39,7 @@
     bool/1,
     int/1,
     float/1,
+    float2str/2,
     map/1,
     utf8_bin/1,
     utf8_str/1,
@@ -258,6 +259,9 @@ float(Num) when is_number(Num) -> erlang:float(Num);
 float(Data) ->
     error({invalid_number, Data}).
 
+float2str(Float, Precision) when is_float(Float) and is_integer(Precision) ->
+    float_to_binary(Float, [{decimals, Precision}, compact]).
+
 map(Bin) when is_binary(Bin) ->
     case emqx_json:decode(Bin, [return_maps]) of
         Map = #{} -> Map;

apps/emqx_rule_engine/src/emqx_rule_funcs.erl

@@ -103,6 +103,7 @@
     int/1,
     float/1,
     float/2,
+    float2str/2,
     map/1,
     bin2hexstr/1,
     hexstr2bin/1
@@ -616,6 +617,9 @@ float(Data, Decimals) when Decimals > 0 ->
     Data1 = ?MODULE:float(Data),
     list_to_float(float_to_list(Data1, [{decimals, Decimals}])).
 
+float2str(Float, Precision) ->
+    emqx_plugin_libs_rule:float2str(Float, Precision).
+
 map(Data) ->
     emqx_plugin_libs_rule:map(Data).
 

apps/emqx_rule_engine/test/emqx_rule_funcs_SUITE.erl

@@ -169,6 +169,11 @@ t_term_encode(_) ->
         end,
         TestData
     ).
+t_float2str(_) ->
+    ?assertEqual(<<"20.2">>, emqx_rule_funcs:float2str(20.2, 1)),
+    ?assertEqual(<<"20.2">>, emqx_rule_funcs:float2str(20.2, 10)),
+    ?assertEqual(<<"20.199999999999999">>, emqx_rule_funcs:float2str(20.2, 15)),
+    ?assertEqual(<<"20.1999999999999993">>, emqx_rule_funcs:float2str(20.2, 16)).
 
 t_hexstr2bin(_) ->
     ?assertEqual(<<6, 54, 79>>, emqx_rule_funcs:hexstr2bin(<<"6364f">>)),