1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
// Package query performs JSONPath-like queries on a TOML document.
//
// The query path implementation is based loosely on the JSONPath specification:
// http://goessner.net/articles/JsonPath/.
//
// The idea behind a query path is to allow quick access to any element, or set
// of elements within TOML document, with a single expression.
//
// result, err := query.CompileAndExecute("$.foo.bar.baz", tree)
//
// This is roughly equivalent to:
//
// next := tree.Get("foo")
// if next != nil {
// next = next.Get("bar")
// if next != nil {
// next = next.Get("baz")
// }
// }
// result := next
//
// err is nil if any parsing exception occurs.
//
// If no node in the tree matches the query, result will simply contain an empty list of
// items.
//
// As illustrated above, the query path is much more efficient, especially since
// the structure of the TOML file can vary. Rather than making assumptions about
// a document's structure, a query allows the programmer to make structured
// requests into the document, and get zero or more values as a result.
//
// Query syntax
//
// The syntax of a query begins with a root token, followed by any number
// sub-expressions:
//
// $
// Root of the TOML tree. This must always come first.
// .name
// Selects child of this node, where 'name' is a TOML key
// name.
// ['name']
// Selects child of this node, where 'name' is a string
// containing a TOML key name.
// [index]
// Selcts child array element at 'index'.
// ..expr
// Recursively selects all children, filtered by an a union,
// index, or slice expression.
// ..*
// Recursive selection of all nodes at this point in the
// tree.
// .*
// Selects all children of the current node.
// [expr,expr]
// Union operator - a logical 'or' grouping of two or more
// sub-expressions: index, key name, or filter.
// [start:end:step]
// Slice operator - selects array elements from start to
// end-1, at the given step. All three arguments are
// optional.
// [?(filter)]
// Named filter expression - the function 'filter' is
// used to filter children at this node.
//
// Query Indexes And Slices
//
// Index expressions perform no bounds checking, and will contribute no
// values to the result set if the provided index or index range is invalid.
// Negative indexes represent values from the end of the array, counting backwards.
//
// // select the last index of the array named 'foo'
// query.CompileAndExecute("$.foo[-1]", tree)
//
// Slice expressions are supported, by using ':' to separate a start/end index pair.
//
// // select up to the first five elements in the array
// query.CompileAndExecute("$.foo[0:5]", tree)
//
// Slice expressions also allow negative indexes for the start and stop
// arguments.
//
// // select all array elements.
// query.CompileAndExecute("$.foo[0:-1]", tree)
//
// Slice expressions may have an optional stride/step parameter:
//
// // select every other element
// query.CompileAndExecute("$.foo[0:-1:2]", tree)
//
// Slice start and end parameters are also optional:
//
// // these are all equivalent and select all the values in the array
// query.CompileAndExecute("$.foo[:]", tree)
// query.CompileAndExecute("$.foo[0:]", tree)
// query.CompileAndExecute("$.foo[:-1]", tree)
// query.CompileAndExecute("$.foo[0:-1:]", tree)
// query.CompileAndExecute("$.foo[::1]", tree)
// query.CompileAndExecute("$.foo[0::1]", tree)
// query.CompileAndExecute("$.foo[:-1:1]", tree)
// query.CompileAndExecute("$.foo[0:-1:1]", tree)
//
// Query Filters
//
// Query filters are used within a Union [,] or single Filter [] expression.
// A filter only allows nodes that qualify through to the next expression,
// and/or into the result set.
//
// // returns children of foo that are permitted by the 'bar' filter.
// query.CompileAndExecute("$.foo[?(bar)]", tree)
//
// There are several filters provided with the library:
//
// tree
// Allows nodes of type Tree.
// int
// Allows nodes of type int64.
// float
// Allows nodes of type float64.
// string
// Allows nodes of type string.
// time
// Allows nodes of type time.Time.
// bool
// Allows nodes of type bool.
//
// Query Results
//
// An executed query returns a Result object. This contains the nodes
// in the TOML tree that qualify the query expression. Position information
// is also available for each value in the set.
//
// // display the results of a query
// results := query.CompileAndExecute("$.foo.bar.baz", tree)
// for idx, value := results.Values() {
// fmt.Println("%v: %v", results.Positions()[idx], value)
// }
//
// Compiled Queries
//
// Queries may be executed directly on a Tree object, or compiled ahead
// of time and executed discretely. The former is more convenient, but has the
// penalty of having to recompile the query expression each time.
//
// // basic query
// results := query.CompileAndExecute("$.foo.bar.baz", tree)
//
// // compiled query
// query, err := toml.Compile("$.foo.bar.baz")
// results := query.Execute(tree)
//
// // run the compiled query again on a different tree
// moreResults := query.Execute(anotherTree)
//
// User Defined Query Filters
//
// Filter expressions may also be user defined by using the SetFilter()
// function on the Query object. The function must return true/false, which
// signifies if the passed node is kept or discarded, respectively.
//
// // create a query that references a user-defined filter
// query, _ := query.Compile("$[?(bazOnly)]")
//
// // define the filter, and assign it to the query
// query.SetFilter("bazOnly", func(node interface{}) bool{
// if tree, ok := node.(*Tree); ok {
// return tree.Has("baz")
// }
// return false // reject all other node types
// })
//
// // run the query
// query.Execute(tree)
//
package query
|
