cue-lang/cue v0.16.0-alpha.2

on GitHub

Changes which may break some users are marked below with: ⚠️

Language

As a reminder, we have two ongoing language experiments since v0.15; a replacement for struct embedding and a rework of aliases. Please give these a try and report any issues or feedback!

The new try experiment

This experiment adds a try clause in comprehensions as well as the use of ? in field selectors. This addition to the language intends to provide a more concise syntax for handling optional fields without the risk of unintentionally swallowing errors.

You can try this experiment by following our how-to guide. For more information, see the proposal on GitHub and the spec change patch.

The new else comprehension clause

This change adds an optional else clause for CUE modules targetting the language version v0.16.0 or later. With this addition to the language, an if or for comprehension may be followed by an else clause which triggers when the comprehension produces zero values.

Note that this feature is not an experiment; it is available to any CUE module targetting the language version v0.16.0 or later.

You can try this feature by following our how-to guide. For more information, see the full patch which includes the changes to the spec, or read the pre-release version of the language spec.

Evaluator

A number of changes were made to improve support for using cue.Values concurrently; see Issue #2733 for more details and ongoing progress.

A number of panics and other bugs in the evaluator which were reported since v0.15.0 have been fixed; thank you to all who reported these.

cmd/cue

The global --verbose and --trace flags have been moved to the cue get go and cue trim commands respectively, as they were the only ones actually using those flags, and this could be confusing to users.

Fix a bug where loading ./...:pkgname could lead to loading directories with zero CUE files as instances, which could cause poor performance for CUE packages with multiple parent directories.

LSP server

Code Actions: two code actions are now provided, Add surrounding struct braces and Remove surrounding struct braces, which convert between

a: b: c

and

a: {
	b: c
}

with the cursor on b.

Initial LSP support for editing embedded JSON files. This feature provides completions and hover-docs when editing JSON files which are embedded into CUE via the @embed attribute. A teaser video is available on YouTube. Support for embedded YAML files will appear soon.

Several bug fixes, including better behaviour for files and directories with spaces; improvements for value aliases (foo: L=x); LSP rename now provides placeholder text.

See our Getting Started wiki page for instructions on how to set it up with your editor.

Please report any bugs or missing features you encounter via the Issue tracker or via the #lsp channels on Discord or Slack.

Encodings

Add support for encoding YAML tags like key: !Custom value by using CUE attributes like key: "value" @yaml(,tag="!Custom").

Standard library

The net package adds CompareIP to compare two IP addresses, which can be useful for computing with IP ranges.

The net/http package adds Serve as an experimental API to listen on a port and serve HTTP requests.

The tool/file package adds Symlink to create symbolic links.

Go API

cue/ast gains the NewPredeclared and Ident.IsPredeclared to mark and detect identifiers referencing predeclared names like error or int rather than fields which may shadow those names in the current scope.

⚠️ cue/token.Compare now sorts absolute paths before relative ones, to ensure consistent behavior between Unix-like systems and Windows.

⚠️ The long-deprecated and hidden cue.Instance.Eval method is now removed.