github.com/dolthub/dolt/go@v0.40.5-0.20240520175717-68db7794bea6/libraries/utils/minver/minver.go (about)

     1  // Copyright 2024 Dolthub, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package minver
    16  
    17  import (
    18  	"fmt"
    19  	"reflect"
    20  	"strings"
    21  
    22  	"gopkg.in/yaml.v2"
    23  
    24  	"github.com/dolthub/dolt/go/libraries/utils/version"
    25  )
    26  
    27  func YamlForVersion(st any, versionNum uint32) ([]byte, error) {
    28  	err := NullUnsupported(versionNum, st)
    29  	if err != nil {
    30  		return nil, fmt.Errorf("error nulling unspported fields for version %d: %w", versionNum, err)
    31  	}
    32  
    33  	return yaml.Marshal(st)
    34  }
    35  
    36  func NullUnsupported(verNum uint32, st any) error {
    37  	const tagName = "minver"
    38  
    39  	// use reflection to loop over all fields in the struct st
    40  	// for each field check the tag "minver" and if the current version is less than that, set the field to nil
    41  	t := reflect.TypeOf(st)
    42  
    43  	if t.Kind() != reflect.Ptr {
    44  		return fmt.Errorf("expected a pointer to a struct, got %T", st)
    45  	} else if t.Kind() == reflect.Ptr {
    46  		t = t.Elem()
    47  	}
    48  
    49  	// Iterate over all available fields and read the tag value
    50  	for i := 0; i < t.NumField(); i++ {
    51  		// Get the field, returns https://golang.org/pkg/reflect/#StructField
    52  		field := t.Field(i)
    53  
    54  		// Get the field tag value
    55  		tag := field.Tag.Get(tagName)
    56  
    57  		if tag != "" {
    58  			// if it's nullable check to see if it should be set to nil
    59  			if field.Type.Kind() == reflect.Ptr || field.Type.Kind() == reflect.Slice || field.Type.Kind() == reflect.Map {
    60  				var setToNull bool
    61  
    62  				if tag == "TBD" {
    63  					setToNull = true
    64  				} else {
    65  					minver, err := version.Encode(tag)
    66  					if err != nil {
    67  						return fmt.Errorf("invalid version tag '%s' on field '%s': %w", tag, field.Name, err)
    68  					}
    69  
    70  					setToNull = verNum < minver
    71  				}
    72  
    73  				if setToNull {
    74  					// Get the field value
    75  					v := reflect.ValueOf(st).Elem().Field(i)
    76  					v.Set(reflect.Zero(v.Type()))
    77  				}
    78  			} else {
    79  				return fmt.Errorf("non-nullable field '%s' has a version tag '%s'", field.Name, tag)
    80  			}
    81  
    82  			var hasOmitEmpty bool
    83  			yamlTag := field.Tag.Get("yaml")
    84  			if yamlTag != "" {
    85  				vals := strings.Split(yamlTag, ",")
    86  				for _, val := range vals {
    87  					if val == "omitempty" {
    88  						hasOmitEmpty = true
    89  						break
    90  					}
    91  				}
    92  			}
    93  
    94  			if !hasOmitEmpty {
    95  				return fmt.Errorf("field '%s' has a version tag '%s' but no yaml tag with omitempty", field.Name, tag)
    96  			}
    97  		}
    98  
    99  		v := reflect.ValueOf(st).Elem().Field(i)
   100  
   101  		vIsNullable := v.Type().Kind() == reflect.Ptr || v.Type().Kind() == reflect.Slice || v.Type().Kind() == reflect.Map
   102  
   103  		if !vIsNullable || !v.IsNil() {
   104  			// if the field is a pointer to a struct, or a struct, or a slice recurse
   105  			if field.Type.Kind() == reflect.Ptr && field.Type.Elem().Kind() == reflect.Struct {
   106  				err := NullUnsupported(verNum, v.Interface())
   107  				if err != nil {
   108  					return err
   109  				}
   110  			} else if field.Type.Kind() == reflect.Struct {
   111  				err := NullUnsupported(verNum, v.Addr().Interface())
   112  				if err != nil {
   113  					return err
   114  				}
   115  			} else if field.Type.Kind() == reflect.Slice {
   116  				if field.Type.Elem().Kind() == reflect.Ptr && field.Type.Elem().Elem().Kind() == reflect.Struct {
   117  					for i := 0; i < v.Len(); i++ {
   118  						err := NullUnsupported(verNum, v.Index(i).Interface())
   119  						if err != nil {
   120  							return err
   121  						}
   122  					}
   123  				} else if field.Type.Elem().Kind() == reflect.Struct {
   124  					for i := 0; i < v.Len(); i++ {
   125  						err := NullUnsupported(verNum, v.Index(i).Addr().Interface())
   126  						if err != nil {
   127  							return err
   128  						}
   129  					}
   130  				}
   131  			}
   132  		}
   133  	}
   134  
   135  	return nil
   136  }