Minor release to address documentation gaps and additional methods to make unknowns more useful

Fixes

• Helpers for accessing unknown state information [#781]

Full Changelog: v0.17.0...v0.17.1

At a high-level this release introduces several changes which should improve ease of use
while also improving the evaluation safety and quality:

• Standard library functions may be extended by using cel.Function options.
• The unknown type now contains information about which field references were unknown.
• Type representations have been consolidated to *types.Type.
• New options have been added to add custom AST validations which are run after type-checking.
• Additional macros were added for optional types, and a new extension was added for list slicing.
• The cel.ContextProtoVars method has been added to bind proto fields to variable names,
  complementing cel.DeclareContextProto.

Features

• Unify decls.Type with types.Type [#745]
• Introduce optFlatMap and OptionalTypes documentation [#744]
• Include expression id on parser and checker errors [#725]
• Implement errors.Unwrap for types.Err. [#728]
• Allow extension of stdlib functions [#747]
• Add list library with slice method [#753]
• Export FormatCELType in the 'cel' package [#763]
• Validators for common literals and use cases [#765]
• Comprehension nesting limit validator [#769]
• Unify type adapter / provider representations [#770]
• Benchmark harness with some initial reference cases [#750]
• Simplified partial state evaluation [#766]
• Update types.Unknown with attribute trails [#776]
• ContextProtoVars() to simplify proto-based inputs [#779]
• Variadic logical operator AST support [#726]

Fixes

• Add the overload reference for optional field selection [#730]
• Correct a typo in the README [#731]
• Clear iteration variable data during expression pruning [#740]
• Restore iter range pruning on comprehension ASTs [#757]

Breaking Changes

The following API changes may break users of cel-go:

• Removal of *types.TypeValue, replaced by *types.Type
• Removal of *exprpb.Type from public interfaces such as the checker.AstNode
• Change in type definition for *types.Unknown. Switch from a type alias for []int64 to a structured type.

New Contributors

• @Ido-Itz made their first contribution in #731
• @chancez made their first contribution in #753

Full Changelog: v0.16.0...v0.17.0

Features

• Expose ExpressionSizeCodePointLimit as env option. [#720]
• Presence test cost tracking options [#721]
• Support for optMap() optional value macro [#717]

Fixes

• Bump socket.io-parser from 4.2.2 to 4.2.3 in /repl/appengine/web [#713]
• Fix for macro call tracking with optional list elements by [#712]
• Bump google.golang.org/genproto [#714]
• Add vendor integrity check [#716]
• Fix overload collision checks by ignoring type param names [#718]

New Contributors

• @liggitt made their first contribution in #714
• @notyourusualaccountname2 made their first contribution in #720

Full Changelog: v0.15.3...v0.16.0

Fixes

• Fix state tracking through optional field selections [#708]
• Support for pruning macro call nodes with limited optional support [#705]
• Update presence test state tracking and pruning [#711]

PR #711 also fixes an issue where optional values would not work
correctly with partial state tracking in some cases.

Full Changelog: v0.15.2...v0.15.3

Fixes

• Make checker state concurrency safe [#702]
• AST scan to establish a non-conflicting expression ID for pruning [#703]

Full Changelog: v0.15.1...v0.15.2

Fixes

• Bump engine.io from 6.4.1 to 6.4.2 [#697]
• Fix ID collision between partial eval and AST pruner [#700]

Full Changelog: v0.15.0...v0.15.1

Features

This release introduces a new feature for CEL which allows you to package up local variable
bindings within your expression, using the following syntax:

cel.bind(<varName>, <varInitExpr>, <remainingExpr>)

An example would look as follows:

cel.bind(vals, msg.nested_msg.repeated_strings,
    vals.size() > 2 && 
    vals[0].startsWith('prefix') && 
    vals[1].endsWith('suffix'))

• CEL variable bindings [#682]
• Expose optional types as a REPL option [#675]
• Extension library for set-based tests over lists [#689]

Fixes

• Parser error reporting limit [#672]
• Prune recursion fixes for nested logic [#677]
• Add help and compile options to the REPL [#676]
• Fix for type guard on optimized set membership step [#678]
• Fix numeric unparsing for floats which represent integer values by [#686]
• Update ANTLR v4 WORKSPACE references [#691]
• Fix error message generation for parse-only expressions [#693]
• Additional string.format() test for message field accesses [#694]

Breaking changes

• Update the ConvertToNative API documentation and strings.join implementation [#692]

The strings.join implementation had previously been based on ConvertToNative, but this
presented some usability issues and the implementation was shifted to rely on ref.Val and
traits.Iterator. The new implementation can be opted into by using ext.StringsVersion(2),
or opted out of by using a version < 2.

Full Changelog: v0.14.0...v0.15.0

Features

• Support for protobuf JSON serialization of native object types [#616]
• Allow creation of custom types.Err structs [#630]

Optional Values

• Syntax, type-checking, and runtime support for optional list elements [#615]
• Support for optional on unparse [#673]

String Extensions

• Add string.format by [#617]
• Add version option to Strings extension library [#650]
• Add strings.quote [#639]
• Add estimated cost support to strings.quote [#664]
• Add compile-time string.format checking [#645]

REPL

• Appengine demo for web-based REPL [#646]
• Enable extensions for REPL [#653]
• Update REPL to use ext.Strings formatter when possible. [#659]

Fixes

• Fix long build times by upgrading gazelle [#637]
• Ensure that macro call tracking is updated during AST pruning [#619]
• Fix accidental alterations to 'decorators' slice [#620]
• Tests for race conditions in top-level cel package [#625]
• Potential index out of bounds fix by [#626]
• Fix conformance service proto field access for SourcePosition message [#627]
• Ensure that optional indices are within the range of elements [#663]
• Update repl README's standalone build commands [#636]
• Fix panic in optimized set membership test for byte values [#652]
• Fix regression of cost behavior for has() [#651]

Breaking Changes

• Remove the deprecated interpreter.Coster interface [#665]

Since the Env.EstimateCost() and Program.ActualCost() routines are available,
the deprecated cel.EstimateCost() routine is confusing and strictly less accurate
than the updated APIs.

While there are other cleanups desired for https://github.com/google/cel-go/issues/504,
this change will at least improves the clarity of the top-level APIs.

Note: this is a breaking change. Users should consult the referenced methods
to replace any legacy use of cel.EstimateCost()

New Contributors

• @inteon made their first contribution in #620
• @nlachfr made their first contribution in #630
• @davidjb made their first contribution in #636
• @dependabot made their first contribution in #647
• @SimonWaldherr made their first contribution in #670

Full Changelog: v0.13.0...v0.14.0

Fixes

• Thread-safety fix for unprotected mutation of decorator set [#623]

Full Changelog: v0.12.5...v0.12.6

Fixes

• Thread-safety fix for unprotected mutation of decorator set [#622]

Full Changelog: v0.11.5...v0.11.6