Do not marshal python_requirements if it is empty (#2306)

Author: 8W9aG

pkg/config/config.go

@@ -47,7 +47,7 @@ type RunItem struct {
 type Build struct {
 	GPU                bool      `json:"gpu,omitempty" yaml:"gpu,omitempty"`
 	PythonVersion      string    `json:"python_version,omitempty" yaml:"python_version"`
-	PythonRequirements string    `json:"python_requirements,omitempty" yaml:"python_requirements"`
+	PythonRequirements string    `json:"python_requirements,omitempty" yaml:"python_requirements,omitempty"`
 	PythonPackages     []string  `json:"python_packages,omitempty" yaml:"python_packages,omitempty"` // Deprecated, but included for backwards compatibility
 	Run                []RunItem `json:"run,omitempty" yaml:"run,omitempty"`
 	SystemPackages     []string  `json:"system_packages,omitempty" yaml:"system_packages,omitempty"`

pkg/config/config_test.go

@@ -726,7 +726,6 @@ func TestConfigMarshal(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, `build:
   python_version: "3.12"
-  python_requirements: ""
   fast: false
 predict: ""
 `, string(data))