cuelang.org/go@v0.13.0/encoding/yaml/yaml.go (about)

     1  // Copyright 2019 The CUE Authors
     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 yaml converts YAML encodings to and from CUE. When converting to CUE,
    16  // comments and position information are retained.
    17  package yaml
    18  
    19  import (
    20  	"bytes"
    21  	"io"
    22  
    23  	"cuelang.org/go/cue"
    24  	"cuelang.org/go/cue/ast"
    25  	cueyaml "cuelang.org/go/internal/encoding/yaml"
    26  	"cuelang.org/go/internal/source"
    27  	"cuelang.org/go/internal/value"
    28  )
    29  
    30  // Extract parses the YAML specified by src to a CUE expression. If
    31  // there's more than one document, the documents will be returned as a
    32  // list. The src argument may be a nil, string, []byte, or io.Reader. If
    33  // src is nil, the result of reading the file specified by filename will
    34  // be used.
    35  func Extract(filename string, src interface{}) (*ast.File, error) {
    36  	data, err := source.ReadAll(filename, src)
    37  	if err != nil {
    38  		return nil, err
    39  	}
    40  	a := []ast.Expr{}
    41  	d := cueyaml.NewDecoder(filename, data)
    42  	for {
    43  		expr, err := d.Decode()
    44  		if err != nil {
    45  			if err != io.EOF {
    46  				return nil, err
    47  			}
    48  			if expr != nil {
    49  				a = append(a, expr)
    50  			}
    51  			break
    52  		}
    53  		a = append(a, expr)
    54  	}
    55  	f := &ast.File{Filename: filename}
    56  	switch len(a) {
    57  	case 0:
    58  	case 1:
    59  		switch x := a[0].(type) {
    60  		case *ast.StructLit:
    61  			f.Decls = x.Elts
    62  		default:
    63  			f.Decls = []ast.Decl{&ast.EmbedDecl{Expr: x}}
    64  		}
    65  	default:
    66  		f.Decls = []ast.Decl{&ast.EmbedDecl{Expr: &ast.ListLit{Elts: a}}}
    67  	}
    68  	return f, nil
    69  }
    70  
    71  // Encode returns the YAML encoding of v.
    72  func Encode(v cue.Value) ([]byte, error) {
    73  	n := v.Syntax(cue.Final())
    74  	b, err := cueyaml.Encode(n)
    75  	return b, err
    76  }
    77  
    78  // EncodeStream returns the YAML encoding of iter, where consecutive values
    79  // of iter are separated with a `---`.
    80  func EncodeStream(iter cue.Iterator) ([]byte, error) {
    81  	// TODO: return an io.Reader and allow asynchronous processing.
    82  	buf := &bytes.Buffer{}
    83  	for i := 0; iter.Next(); i++ {
    84  		if i > 0 {
    85  			buf.WriteString("---\n")
    86  		}
    87  		n := iter.Value().Syntax(cue.Final())
    88  		b, err := cueyaml.Encode(n)
    89  		if err != nil {
    90  			return nil, err
    91  		}
    92  		buf.Write(b)
    93  	}
    94  	return buf.Bytes(), nil
    95  }
    96  
    97  // Validate validates the YAML and confirms it matches the constraints
    98  // specified by v. For YAML streams, all values must match v.
    99  func Validate(b []byte, v cue.Value) error {
   100  	ctx := value.OpContext(v)
   101  	_, err := cueyaml.Validate(ctx, b, v)
   102  	return err
   103  }