Support exec input plugin legacy behavior

internal/config/config.go

@@ -611,7 +611,10 @@ func buildParser(name string, tbl *ast.Table) (parsers.Parser, error) {
 		}
 	}
 
-	if c.DataFormat == "" {
+	// Legacy support, exec plugin originally parsed JSON by default.
+	if name == "exec" && c.DataFormat == "" {
+		c.DataFormat = "json"
+	} else if c.DataFormat == "" {
 		c.DataFormat = "influx"
 	}
 

internal/config/config_test.go

@@ -92,7 +92,7 @@ func TestConfig_LoadDirectory(t *testing.T) {
 		"Testdata did not produce correct memcached metadata.")
 
 	ex := inputs.Inputs["exec"]().(*exec.Exec)
-	p, err := parsers.NewInfluxParser()
+	p, err := parsers.NewJSONParser("exec", nil, nil)
 	assert.NoError(t, err)
 	ex.SetParser(p)
 	ex.Command = "/usr/bin/myothercollector --foo=bar"