manual.go

Documentation: cuelang.org/go/pkg/encoding/json

     1  // Copyright 2018 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 json
    16  
    17  import (
    18  	"bytes"
    19  	"encoding/json"
    20  	"fmt"
    21  	"io"
    22  	"strings"
    23  
    24  	"cuelang.org/go/cue"
    25  	"cuelang.org/go/cue/ast"
    26  	"cuelang.org/go/cue/errors"
    27  	"cuelang.org/go/cue/parser"
    28  	"cuelang.org/go/cue/token"
    29  	cuejson "cuelang.org/go/encoding/json"
    30  	internaljson "cuelang.org/go/internal/encoding/json"
    31  )
    32  
    33  // Compact generates the JSON-encoded src with insignificant space characters
    34  // elided.
    35  func Compact(src []byte) (string, error) {
    36  	dst := bytes.Buffer{}
    37  	if err := json.Compact(&dst, src); err != nil {
    38  		return "", err
    39  	}
    40  	return dst.String(), nil
    41  }
    42  
    43  // Indent creates an indented form of the JSON-encoded src.
    44  // Each element in a JSON object or array begins on a new,
    45  // indented line beginning with prefix followed by one or more
    46  // copies of indent according to the indentation nesting.
    47  // The data appended to dst does not begin with the prefix nor
    48  // any indentation, to make it easier to embed inside other formatted JSON data.
    49  // Although leading space characters (space, tab, carriage return, newline)
    50  // at the beginning of src are dropped, trailing space characters
    51  // at the end of src are preserved and copied to dst.
    52  // For example, if src has no trailing spaces, neither will dst;
    53  // if src ends in a trailing newline, so will dst.
    54  func Indent(src []byte, prefix, indent string) (string, error) {
    55  	dst := bytes.Buffer{}
    56  	if err := json.Indent(&dst, src, prefix, indent); err != nil {
    57  		return "", err
    58  	}
    59  	return dst.String(), nil
    60  }
    61  
    62  // HTMLEscape returns the JSON-encoded src with <, >, &, U+2028 and
    63  // U+2029 characters inside string literals changed to \u003c, \u003e, \u0026,
    64  // \u2028, \u2029 so that the JSON will be safe to embed inside HTML <script>
    65  // tags. For historical reasons, web browsers don't honor standard HTML escaping
    66  // within <script> tags, so an alternative JSON encoding must be used.
    67  func HTMLEscape(src []byte) string {
    68  	dst := &bytes.Buffer{}
    69  	json.HTMLEscape(dst, src)
    70  	return dst.String()
    71  }
    72  
    73  // Marshal returns the JSON encoding of v.
    74  func Marshal(v cue.Value) (string, error) {
    75  	b, err := internaljson.Marshal(v)
    76  	return string(b), err
    77  }
    78  
    79  // MarshalStream turns a list into a stream of JSON objects.
    80  func MarshalStream(v cue.Value) (string, error) {
    81  	// TODO: return an io.Reader and allow asynchronous processing.
    82  	iter, err := v.List()
    83  	if err != nil {
    84  		return "", err
    85  	}
    86  	var b strings.Builder
    87  	for iter.Next() {
    88  		p, err := internaljson.Marshal(iter.Value())
    89  		if err != nil {
    90  			return "", err
    91  		}
    92  		b.Write(p)
    93  		b.WriteByte('\n')
    94  	}
    95  	return b.String(), nil
    96  }
    97  
    98  // UnmarshalStream parses the JSON to a CUE instance.
    99  func UnmarshalStream(data []byte) (ast.Expr, error) {
   100  	var r cue.Runtime
   101  	d := cuejson.NewDecoder(&r, "", bytes.NewReader(data))
   102  
   103  	a := []ast.Expr{}
   104  	for {
   105  		x, err := d.Extract()
   106  		if err == io.EOF {
   107  			break
   108  		}
   109  		if err != nil {
   110  			return nil, err
   111  		}
   112  		a = append(a, x)
   113  	}
   114  
   115  	return ast.NewList(a...), nil
   116  }
   117  
   118  // Unmarshal parses the JSON-encoded data.
   119  func Unmarshal(b []byte) (ast.Expr, error) {
   120  	if !json.Valid(b) {
   121  		return nil, fmt.Errorf("json: invalid JSON")
   122  	}
   123  	expr, err := parser.ParseExpr("json", b)
   124  	if err != nil {
   125  		// NOTE: should never happen.
   126  		return nil, errors.Wrapf(err, token.NoPos, "json: could not parse JSON")
   127  	}
   128  	return expr, nil
   129  }
   130  
   131  // Validate validates JSON and confirms it matches the constraints
   132  // specified by v.
   133  func Validate(b []byte, v cue.Value) (bool, error) {
   134  	err := cuejson.Validate(b, v)
   135  	if err != nil {
   136  		return false, err
   137  	}
   138  	return true, nil
   139  }
   140
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