ext

func Bindings ¶ added in v0.15.0

func Bindings() cel.EnvOption

Bindings returns a cel.EnvOption to configure support for local variable bindings in expressions.

Cel.Bind ¶

Binds a simple identifier to an initialization expression which may be used in a subsequenct result expression. Bindings may also be nested within each other.

cel.bind(<varName>, <initExpr>, <resultExpr>)

Examples:

cel.bind(a, 'hello',
cel.bind(b, 'world', a + b + b + a)) // "helloworldworldhello"

// Avoid a list allocation within the exists comprehension.
cel.bind(valid_values, [a, b, c],
[d, e, f].exists(elem, elem in valid_values))

Local bindings are not guaranteed to be evaluated before use.

func Encoders ¶ added in v0.6.0

func Encoders() cel.EnvOption

Encoders returns a cel.EnvOption to configure extended functions for string, byte, and object encodings.

Base64.Decode ¶

Decodes base64-encoded string to bytes.

This function will return an error if the string input is not base64-encoded.

base64.decode(<string>) -> <bytes>

Examples:

base64.decode('aGVsbG8=')  // return b'hello'
base64.decode('aGVsbG8')   // error

Base64.Encode ¶

Encodes bytes to a base64-encoded string.

base64.encode(<bytes>)  -> <string>

Examples:

base64.encode(b'hello') // return b'aGVsbG8='

func FormatString ¶ added in v0.14.0

func FormatString(arg ref.Val, locale string) (string, error)

FormatString returns the string representation of a CEL value.

It is used to implement the %s specifier in the (string).format() extension function.

func Lists ¶ added in v0.17.0

func Lists() cel.EnvOption

Lists returns a cel.EnvOption to configure extended functions for list manipulation. As a general note, all indices are zero-based. # Slice

Returns a new sub-list using the indexes provided.

<list>.slice(<int>, <int>) -> <list>

Examples:

[1,2,3,4].slice(1, 3) // return [2, 3]
[1,2,3,4].slice(2, 4) // return [3 ,4]

func Math ¶ added in v0.13.0

func Math() cel.EnvOption

Math returns a cel.EnvOption to configure namespaced math helper macros and functions.

Note, all macros use the 'math' namespace; however, at the time of macro expansion the namespace looks just like any other identifier. If you are currently using a variable named 'math', the macro will likely work just as intended; however, there is some chance for collision.

Math.Greatest ¶

Returns the greatest valued number present in the arguments to the macro.

Greatest is a variable argument count macro which must take at least one argument. Simple numeric and list literals are supported as valid argument types; however, other literals will be flagged as errors during macro expansion. If the argument expression does not resolve to a numeric or list(numeric) type during type-checking, or during runtime then an error will be produced. If a list argument is empty, this too will produce an error.

math.greatest(<arg>, ...) -> <double|int|uint>

Examples:

math.greatest(1)      // 1
math.greatest(1u, 2u) // 2u
math.greatest(-42.0, -21.5, -100.0)   // -21.5
math.greatest([-42.0, -21.5, -100.0]) // -21.5
math.greatest(numbers) // numbers must be list(numeric)

math.greatest()         // parse error
math.greatest('string') // parse error
math.greatest(a, b)     // check-time error if a or b is non-numeric
math.greatest(dyn('string')) // runtime error

Math.Least ¶

Returns the least valued number present in the arguments to the macro.

Least is a variable argument count macro which must take at least one argument. Simple numeric and list literals are supported as valid argument types; however, other literals will be flagged as errors during macro expansion. If the argument expression does not resolve to a numeric or list(numeric) type during type-checking, or during runtime then an error will be produced. If a list argument is empty, this too will produce an error.

math.least(<arg>, ...) -> <double|int|uint>

Examples:

math.least(1)      // 1
math.least(1u, 2u) // 1u
math.least(-42.0, -21.5, -100.0)   // -100.0
math.least([-42.0, -21.5, -100.0]) // -100.0
math.least(numbers) // numbers must be list(numeric)

math.least()         // parse error
math.least('string') // parse error
math.least(a, b)     // check-time error if a or b is non-numeric
math.least(dyn('string')) // runtime error

func NativeTypes ¶ added in v0.13.0

func NativeTypes(refTypes ...any) cel.EnvOption

NativeTypes creates a type provider which uses reflect.Type and reflect.Value instances to produce type definitions that can be used within CEL.

All struct types in Go are exposed to CEL via their simple package name and struct type name:

```go package identity

type Account struct {
  ID int
}

```

The type `identity.Account` would be exported to CEL using the same qualified name, e.g. `identity.Account{ID: 1234}` would create a new `Account` instance with the `ID` field populated.

Only exported fields are exposed via NativeTypes, and the type-mapping between Go and CEL is as follows:

| Go type | CEL type | |-------------------------------------|-----------| | bool | bool | | []byte | bytes | | float32, float64 | double | | int, int8, int16, int32, int64 | int | | string | string | | uint, uint8, uint16, uint32, uint64 | uint | | time.Duration | duration | | time.Time | timestamp | | array, slice | list | | map | map |

Please note, if you intend to configure support for proto messages in addition to native types, you will need to provide the protobuf types before the golang native types. The same advice holds if you are using custom type adapters and type providers. The native type provider composes over whichever type adapter and provider is configured in the cel.Env at the time that it is invoked.

func NewSetMembershipOptimizer ¶ added in v0.19.0

func NewSetMembershipOptimizer() (cel.ASTOptimizer, error)

NewSetMembershipOptimizer rewrites set membership tests using the `in` operator against a list of constant values of enum, int, uint, string, or boolean type into a set membership test against a map where the map keys are the elements of the list.

func Protos ¶ added in v0.13.0

func Protos() cel.EnvOption

Protos returns a cel.EnvOption to configure extended macros and functions for proto manipulation.

Note, all macros use the 'proto' namespace; however, at the time of macro expansion the namespace looks just like any other identifier. If you are currently using a variable named 'proto', the macro will likely work just as intended; however, there is some chance for collision.

Protos.GetExt ¶

Macro which generates a select expression that retrieves an extension field from the input proto2 syntax message. If the field is not set, the default value forthe extension field is returned according to safe-traversal semantics.

proto.getExt(<msg>, <fully.qualified.extension.name>) -> <field-type>

Examples:

proto.getExt(msg, google.expr.proto2.test.int32_ext) // returns int value

Protos.HasExt ¶

Macro which generates a test-only select expression that determines whether an extension field is set on a proto2 syntax message.

proto.hasExt(<msg>, <fully.qualified.extension.name>) -> <bool>

Examples:

proto.hasExt(msg, google.expr.proto2.test.int32_ext) // returns true || false

func Sets ¶ added in v0.15.0

func Sets() cel.EnvOption

Sets returns a cel.EnvOption to configure namespaced set relationship functions.

There is no set type within CEL, and while one may be introduced in the future, there are cases where a `list` type is known to behave like a set. For such cases, this library provides some basic functionality for determining set containment, equivalence, and intersection.

Sets.Contains ¶

Returns whether the first list argument contains all elements in the second list argument. The list may contain elements of any type and standard CEL equality is used to determine whether a value exists in both lists. If the second list is empty, the result will always return true.

sets.contains(list(T), list(T)) -> bool

Examples:

sets.contains([], []) // true
sets.contains([], [1]) // false
sets.contains([1, 2, 3, 4], [2, 3]) // true
sets.contains([1, 2.0, 3u], [1.0, 2u, 3]) // true

Sets.Equivalent ¶

Returns whether the first and second list are set equivalent. Lists are set equivalent if for every item in the first list, there is an element in the second which is equal. The lists may not be of the same size as they do not guarantee the elements within them are unique, so size does not factor into the computation.

Examples:

sets.equivalent([], []) // true
sets.equivalent([1], [1, 1]) // true
sets.equivalent([1], [1u, 1.0]) // true
sets.equivalent([1, 2, 3], [3u, 2.0, 1]) // true

Sets.Intersects ¶

Returns whether the first list has at least one element whose value is equal to an element in the second list. If either list is empty, the result will be false.

Examples:

sets.intersects([1], []) // false
sets.intersects([1], [1, 2]) // true
sets.intersects([[1], [2, 3]], [[1, 2], [2, 3.0]]) // true

func Strings ¶

func Strings(options ...StringsOption) cel.EnvOption

Strings returns a cel.EnvOption to configure extended functions for string manipulation. As a general note, all indices are zero-based.

CharAt ¶

Returns the character at the given position. If the position is negative, or greater than the length of the string, the function will produce an error:

<string>.charAt(<int>) -> <string>

Examples:

'hello'.charAt(4)  // return 'o'
'hello'.charAt(5)  // return ''
'hello'.charAt(-1) // error

Format ¶

Introduced at version: 1

Returns a new string with substitutions being performed, printf-style. The valid formatting clauses are:

`%s` - substitutes a string. This can also be used on bools, lists, maps, bytes, Duration and Timestamp, in addition to all numerical types (int, uint, and double). Note that the dot/period decimal separator will always be used when printing a list or map that contains a double, and that null can be passed (which results in the string "null") in addition to types. `%d` - substitutes an integer. `%f` - substitutes a double with fixed-point precision. The default precision is 6, but this can be adjusted. The strings `Infinity`, `-Infinity`, and `NaN` are also valid input for this clause. `%e` - substitutes a double in scientific notation. The default precision is 6, but this can be adjusted. `%b` - substitutes an integer with its equivalent binary string. Can also be used on bools. `%x` - substitutes an integer with its equivalent in hexadecimal, or if given a string or bytes, will output each character's equivalent in hexadecimal. `%X` - same as above, but with A-F capitalized. `%o` - substitutes an integer with its equivalent in octal.

<string>.format(<list>) -> <string>

Examples:

"this is a string: %s\nand an integer: %d".format(["str", 42]) // returns "this is a string: str\nand an integer: 42"
"a double substituted with %%s: %s".format([64.2]) // returns "a double substituted with %s: 64.2"
"string type: %s".format([type(string)]) // returns "string type: string"
"timestamp: %s".format([timestamp("2023-02-03T23:31:20+00:00")]) // returns "timestamp: 2023-02-03T23:31:20Z"
"duration: %s".format([duration("1h45m47s")]) // returns "duration: 6347s"
"%f".format([3.14]) // returns "3.140000"
"scientific notation: %e".format([2.71828]) // returns "scientific notation: 2.718280\u202f\u00d7\u202f10\u2070\u2070"
"5 in binary: %b".format([5]), // returns "5 in binary; 101"
"26 in hex: %x".format([26]), // returns "26 in hex: 1a"
"26 in hex (uppercase): %X".format([26]) // returns "26 in hex (uppercase): 1A"
"30 in octal: %o".format([30]) // returns "30 in octal: 36"
"a map inside a list: %s".format([[1, 2, 3, {"a": "x", "b": "y", "c": "z"}]]) // returns "a map inside a list: [1, 2, 3, {"a":"x", "b":"y", "c":"d"}]"
"true bool: %s - false bool: %s\nbinary bool: %b".format([true, false, true]) // returns "true bool: true - false bool: false\nbinary bool: 1"

Passing an incorrect type (a string to `%b`) is considered an error, as well as attempting to use more formatting clauses than there are arguments (`%d %d %d` while passing two ints, for instance). If compile-time checking is enabled, and the formatting string is a constant, and the argument list is a literal, then letting any arguments go unused/unformatted is also considered an error.

IndexOf ¶

Returns the integer index of the first occurrence of the search string. If the search string is not found the function returns -1.

The function also accepts an optional position from which to begin the substring search. If the substring is the empty string, the index where the search starts is returned (zero or custom).

<string>.indexOf(<string>) -> <int>
<string>.indexOf(<string>, <int>) -> <int>

Examples:

'hello mellow'.indexOf('')         // returns 0
'hello mellow'.indexOf('ello')     // returns 1
'hello mellow'.indexOf('jello')    // returns -1
'hello mellow'.indexOf('', 2)      // returns 2
'hello mellow'.indexOf('ello', 2)  // returns 7
'hello mellow'.indexOf('ello', 20) // error

Join ¶

Returns a new string where the elements of string list are concatenated.

The function also accepts an optional separator which is placed between elements in the resulting string.

<list<string>>.join() -> <string> <list<string>>.join(<string>) -> <string>

Examples:

['hello', 'mellow'].join() // returns 'hellomellow'
['hello', 'mellow'].join(' ') // returns 'hello mellow'
[].join() // returns ''
[].join('/') // returns ''

LastIndexOf ¶

Returns the integer index at the start of the last occurrence of the search string. If the search string is not found the function returns -1.

The function also accepts an optional position which represents the last index to be considered as the beginning of the substring match. If the substring is the empty string, the index where the search starts is returned (string length or custom).

<string>.lastIndexOf(<string>) -> <int>
<string>.lastIndexOf(<string>, <int>) -> <int>

Examples:

'hello mellow'.lastIndexOf('')         // returns 12
'hello mellow'.lastIndexOf('ello')     // returns 7
'hello mellow'.lastIndexOf('jello')    // returns -1
'hello mellow'.lastIndexOf('ello', 6)  // returns 1
'hello mellow'.lastIndexOf('ello', -1) // error

LowerAscii ¶

Returns a new string where all ASCII characters are lower-cased.

This function does not perform Unicode case-mapping for characters outside the ASCII range.

<string>.lowerAscii() -> <string>

Examples:

'TacoCat'.lowerAscii()      // returns 'tacocat'
'TacoCÆt Xii'.lowerAscii()  // returns 'tacocÆt xii'

Strings.Quote ¶

Introduced in version: 1

Takes the given string and makes it safe to print (without any formatting due to escape sequences). If any invalid UTF-8 characters are encountered, they are replaced with \uFFFD.

strings.quote(<string>)

Examples:

strings.quote('single-quote with "double quote"') // returns '"single-quote with \"double quote\""' strings.quote("two escape sequences \a\n") // returns '"two escape sequences \\a\\n"'

Replace ¶

Returns a new string based on the target, which replaces the occurrences of a search string with a replacement string if present. The function accepts an optional limit on the number of substring replacements to be made.

When the replacement limit is 0, the result is the original string. When the limit is a negative number, the function behaves the same as replace all.

<string>.replace(<string>, <string>) -> <string>
<string>.replace(<string>, <string>, <int>) -> <string>

Examples:

'hello hello'.replace('he', 'we')     // returns 'wello wello'
'hello hello'.replace('he', 'we', -1) // returns 'wello wello'
'hello hello'.replace('he', 'we', 1)  // returns 'wello hello'
'hello hello'.replace('he', 'we', 0)  // returns 'hello hello'
'hello hello'.replace('', '_')  // returns '_h_e_l_l_o_ _h_e_l_l_o_'
'hello hello'.replace('h', '')  // returns 'ello ello'

Split ¶

Returns a list of strings split from the input by the given separator. The function accepts an optional argument specifying a limit on the number of substrings produced by the split.

When the split limit is 0, the result is an empty list. When the limit is 1, the result is the target string to split. When the limit is a negative number, the function behaves the same as split all.

<string>.split(<string>) -> <list<string>>
<string>.split(<string>, <int>) -> <list<string>>

Examples:

'hello hello hello'.split(' ')     // returns ['hello', 'hello', 'hello']
'hello hello hello'.split(' ', 0)  // returns []
'hello hello hello'.split(' ', 1)  // returns ['hello hello hello']
'hello hello hello'.split(' ', 2)  // returns ['hello', 'hello hello']
'hello hello hello'.split(' ', -1) // returns ['hello', 'hello', 'hello']

Substring ¶

Returns the substring given a numeric range corresponding to character positions. Optionally may omit the trailing range for a substring from a given character position until the end of a string.

Character offsets are 0-based with an inclusive start range and exclusive end range. It is an error to specify an end range that is lower than the start range, or for either the start or end index to be negative or exceed the string length.

<string>.substring(<int>) -> <string>
<string>.substring(<int>, <int>) -> <string>

Examples:

'tacocat'.substring(4)    // returns 'cat'
'tacocat'.substring(0, 4) // returns 'taco'
'tacocat'.substring(-1)   // error
'tacocat'.substring(2, 1) // error

Trim ¶

Returns a new string which removes the leading and trailing whitespace in the target string. The trim function uses the Unicode definition of whitespace which does not include the zero-width spaces. See: https://en.wikipedia.org/wiki/Whitespace_character#Unicode

<string>.trim() -> <string>

Examples:

'  \ttrim\n    '.trim() // returns 'trim'

UpperAscii ¶

Returns a new string where all ASCII characters are upper-cased.

This function does not perform Unicode case-mapping for characters outside the ASCII range.

<string>.upperAscii() -> <string>

Examples:

'TacoCat'.upperAscii()      // returns 'TACOCAT'
'TacoCÆt Xii'.upperAscii()  // returns 'TACOCÆT XII'

Reverse ¶

Introduced at version: 3

Returns a new string whose characters are the same as the target string, only formatted in reverse order. This function relies on converting strings to rune arrays in order to reverse

<string>.reverse() -> <string>

Examples:

'gums'.reverse() // returns 'smug'
'John Smith'.reverse() // returns 'htimS nhoJ'