This release includes the first experimental version of the new evaluator, as well as many other changes including the ongoing modules experiment. More details below.

As a reminder: users can register their projects with Unity, our regression and performance testing setup. Unity is used to ensure that a project's CUE evaluations do not unexpectedly stop working or regress in performance. Adding your project to Unity not only guarantees that we will not break your tests unexpectedly, but it also helps to improve the quality of each CUE release. Follow this link to learn more about Unity, install it, or get in touch with any questions.

Evaluator

The new evaluator can now be enabled via CUE_EXPERIMENT=evalv3. It is not yet complete, and some known bugs remain, but over 95% of the existing tests are passing and the performance already looks promising. Disjunctions and initial structure sharing are now implemented as well.

Work on this new evaluator will continue during the v0.9 release cycle. We will only turn on the new evaluator by default once we are reasonably confident that there are no significant regressions, which may happen in a future release cycle like v0.10. In the meantime, testing via CUE_EXPERIMENT=evalv3 and bug reports are welcome.

We have also published a more detailed update on the performance umbrella issue, which you can subscribe to for updates. You can also take a look at the Evaluator Roadmap project to see the planned work remaining.

CL 1186144 fixes a number of Environment.up panics involving calls to Value.Expr, which affected users of the Go API as well as the openapi encoding.

CL 1185458 ensures we detect permanent errors for undefined fields earlier, necessary for the permanent errors fix in tools/flow below.

Modules

cmd/cue now supports OAuth2 refresh tokens when interacting with $CUE_REGISTRY, so that the user doesn't have to re-run cue login once their access token expires.

CL 1191618 changes the modules client to treat "forbidden" errors as "not found" when finding which OCI repository contains a CUE module. This should resolve some unexpected "forbidden" failures when dealing with certain OCI registry services.

CL 1192905 adds initial support for the source field in cue.mod/module.cue files, which will soon be used as part of the proposal to determine what files go into a CUE module.

As a reminder, the ongoing and planned work can be seen in the Modules Roadmap, and we continue to hold regular Modules feedback sessions.

Encodings

The Encodings project was kicked off at the last CUE Community Update call. As part of this, we now have an #encodings channel on Slack, as well as an Encodings Roadmap project on GitHub where the ongoing and planned work can be seen.

In this release, the new YAML decoder is available in experimental form and enabled by default, given that all of our tests are already passing. You can disable it via CUE_EXPERIMENT=yamlv3decoder=0. The old YAML decoder will be removed in a future release once we're reasonably confident that no significant regressions are present.

Go API

CL 1187452 teaches tools/flow to fail when a task encounters a permanent error, which were being ignored before.

CL 1191227 adds a cue/token.File.Lines getter method, much like go/token.File.Lines was added in Go 1.21.

CL 1191226 teaches cue/literal.ParseNum to support both positive and negative signs for consistency.

CL 1193030 ensures that cue/load.Instances always returns instances in a deterministic order, in particular when multiple instances share the same directory.

CL 1185361 deprecates cue/load.Config.StdRoot, which has not worked as advertised for some time.

cmd/cue

CL 1189314 adds a cue fmt --check flag to list badly formatted files rather than modifying them directly.

CL 1192180 speeds up cue fmt by ensuring that it only processes each CUE file once, rather than formatting files from parent directories as well.

This release includes a number of fixes detailed below:

CL 1186144 fixes a number of evaluator panics which could be triggered by calling the cue.Value.Expr method, which also happened when using the OpenAPI encoder.

CL 1173100 fixes cue get go panics which might occur when any Go packages are vendored or use imported alias declarations.

CL 1185281 fixes a regression introduced in v0.8.0 which led to some incorrect failures in tools/flow and cue cmd.

This release adds initial support for the CUE Central Registry (details below) and includes a number of fixes and improvements.

As a reminder: users can register their projects with Unity, our regression and performance testing setup. Unity is used to ensure that a project's CUE evaluations do not unexpectedly stop working, or regress in terms of performance. It continues to catch multiple issues with each release. Adding your project to Unity not only guarantees that we will not break your tests (if we do, we will work with you to fix your CUE code), but it also helps to improve the quality of each CUE release. Follow this link to learn more about Unity, install it, or get in touch with any questions.

Modules

This release includes experimental support for the CUE Central Registry at registry.cue.works. We have added a cue login command to log into the Central Registry via a GitHub account, and other commands know how to use these credentials when talking to the registry.

We will share more details about the Central Registry and support for other login mechanisms in the future. For now, we are looking to get early feedback.

To get started with the Central Registry, we have published a tutorial on working with modules and the central registry as well.

CL 1185280 adds cue help modules as a high-level overview of CUE modules as well.

Go API

CL 1185281 reverts a change in v0.8.0 to fix valid uses of tools/flow involving task inputs derived from the evaluation of other tasks.

CL 1185684 removes the last remaining bits of API which supported quoted identifiers, which had already been deprecated and largely unsupported for years.

cmd/cue

CL 1173100 fixes cue get go to avoid panics when dealing with vendored packages or any type aliases which refer to indirectly imported packages.

CL 1185356 tweaks cue/load so that cue fmt is able to format CUE files given directly as arguments even when they belong to different packages.

CL 1185473 deprecates the short-form cue somecmd in favor of cue cmd somecmd, as the former caused a number of bugs and slowness when working out which subcommand to execute.

This release includes experimental support for CUE Modules (more details below), as well as a number of improvements and fixes.

More CLs and refactors have also landed for the core evaluator's performance work. These aren't enabled yet as the work isn't complete; subscribe to the performance umbrella issue to read regular updates.

As a reminder: users can register their projects with Unity, our regression and performance testing setup. Unity is used to ensure that a project's CUE evaluations do not unexpectedly stop working, or regress in terms of performance. It continues to catch multiple issues with each release. Adding your project to Unity not only guarantees that we will not break your tests (if we do, we will work with you to fix your CUE code), but it also helps to improve the quality of each CUE release. Follow this link to learn more about Unity, install it, or get in touch with any questions.

Modules

This release includes experimental support for CUE modules in cmd/cue, as outlined in the updated Modules and package management proposal v3.

Alongside this release, we have published a tutorial on the new website which shows how to publish and fetch modules with a custom module registry.

We have also published the first version of the Modules reference documentation, the canonical documentation page describing how CUE modules work in detail.

Note that support for CUE modules is still experimental and subject to change, and needs to be explicitly enabled via CUE_EXPERIMENT=modules. See cue help environment for more information on the environment variables used below.

CUE maps modules to registries via $CUE_REGISTRY, which supports a simple string configuration format as well as a more detailed CUE configuration format which can be read from disk. See cue help registryconfig for more details.

The new cue mod tidy command rewrites cue.mod/module.cue in its canonical format, adds any missing module dependency requirements, and removes unused ones.

The new cue mod publish command publishes the current module to a module registry.

The new cue mod get command can add a new module dependency, update an existing one, or downgrade an existing one as long as it does not cause any conflict.

When running commands like cue export with CUE_EXPERIMENT=modules, dependencies are automatically fetched from module registries following $CUE_REGISTRY and cached on disk inside $CUE_CACHE_DIR.

CUE Language Server Protocol Implementation

This release includes the first early version of an experimental Language Server Protocol (LSP) implementation for CUE. Whilst it remains experimental, the cmd/cuepls binary is separate from cmd/cue. However at a later date it will most likely to become a subcommand of cmd/cue like cue lsp serve.

We are working on updating the VSCode plugin to use cmd/cuepls, as well as supporting an initial version of a plugin for Neovim. For JetBrains users, we are working with the author of the CUE plugin to understand how best to integrate cmd/cuepls with JetBrains.

We will share announcements once the editor integrations are ready for use, and once more LSP features beyond formatting files are available. Subscribe to the LSP announce discussion, or join us in #cuepls on CUE Slack.

Go API

Note that this version of CUE requires Go 1.21 or later, following our policy to support the latest two stable Go releases just like upstream.

The cue/load package supports the CUE Modules experiment out of the box with the environment variable CUE_EXPERIMENT=modules. Alternatively, a custom registry and authorizer can be configured with the Config.Registry field via the modconfig.NewRegistry API.

cue/load also has a new Config.Env struct field to provide the environment variables used to load CUE modules from registries. It defaults to using os.Environ.

We have also added new Go examples to the cue/load package, including an example demonstrating the use of a CUE modules registry.

CL 1173271 drops support for legacy pkg directories, which have been deprecated since the transition to a cue.mod directory in 2019.

CL 1174069 replaces a few more uses of the deprecated cue.Instance type with cue.InstanceOrValue.

CL 1175779 deprecates the FileOffset and File.Base APIs in cue/token, which were inherited from go/token but never had any effect.

Language

There are no changes to the language in this version.

Spec

CL 1173197 makes the use of the term "builtin function" consistent across the document.

Core Evaluator

CL 1173262 fixes a regression introduced by v0.7.0's upgrade to github.com/cockroachdb/apd/v3 where some arithmetic operations would result in an extra 0 digit.

Encoders

CL 1173689 fixes the YAML encoder so that strings looking like hexadecimal numbers are properly quoted.

Builtins

CL 1173735 replaces the uses of Go's net package with net/netip when dealing with IP addresses, which makes them immutable, comparable, and take less memory.

CL 1173926 adds an IPv6 API to net to check that a value is a valid IPv6 address, mirroring IPv4 and taking advantage of the switch to the Go net/netip package.

CL 1174339 fixes tool/exec so that it correctly applies env defaults in CUE values.

CL 1174623 fixes tool/exec so that it accepts env list values as documented.

cmd/cue

CL 1176194 adds a language.version field to cue.mod/module.cue to track what CUE language version a module was written for. This will become necessary to make future language changes as smooth as possible for CUE users. For example, running cue mod init or cue mod tidy with the v0.8.0 release should add language: version: "v0.8.0" when the field isn't present.

CL 1173892 adds a cue help environment section to document the environment variables used by the CLI, such as CUE_EXPERIMENT and CUE_REGISTRY.

CL 1176665 fixes cue cmd so that legacy commands always get the corresponding CUE schema unified.

CL 1177330 fixes a bug where some evaluation errors in tools/flow and cue cmd were omitted, causing unintended results.

CL 1177546 tweaks cmd/cue so that it obeys the --package flag when the output format is CUE.

This release includes a number of fixes and improvements for the experimental support for CUE modules first released in v0.8.0-alpha.1.

Modules

cue mod tidy gained a --check flag, which succeeds only if the module file contains exactly the required dependencies and also contains a canonical CUE language version.

cmd/cue and cue/load now send a detailed HTTP User-Agent string to CUE registries when sending HTTP requests, including the CUE and Go versions, rather than Go's default net/http user agent string.

cmd/cue now supports CUE_DEBUG=http to print HTTP logging information to stderr in JSON format.

Local builds of cmd/cue, such as running go install ./cmd/cue, now include a proper CUE version, allowing cue mod init and cue mod tidy to insert language.version as expected.

This release includes a number of fixes and improvements for the experimental support for CUE modules first released in v0.8.0-alpha.1.

Modules

A new cue mod get command is added, which can add a new module dependency, update an existing one, or downgrade an existing one as long as it does not cause any conflict.

The cue/load package has a new Config.Env struct field to provide the environment variables used to load CUE modules from registries.

A new cue help registryconfig documentation section has been added, explaining how $CUE_REGISTRY works as well as the configuration file schema it supports.

This release includes a number of fixes and improvements for the experimental support for CUE modules first released in v0.8.0-alpha.1.

Thank you to @kharf, @mvdan, @myitcv, @nickfiggins, and @rogpeppe for contributing to this release!

Modules

The cue/load package now supports loading CUE instances using the CUE Modules experiment, which was first added to cmd/cue in v0.8.0-alpha.1.

cue/load supports the CUE Modules experiment out of the box with the environment variable CUE_EXPERIMENT=modules. Alternatively, a custom registry and authorizer can be configured with the Config.Registry field via the modconfig.NewRegistry API.

We have also added new Go examples to the cue/load package, including an example demonstrating the use of a CUE modules registry.

Other changes

CL 1177330 fixes a bug where some evaluation errors in tools/flow and cue cmd were omitted, causing unintended results.

CL 1177546 tweaks cmd/cue so that it obeys the --package flag when the output format is CUE.

This release includes a number of fixes and improvements for the experimental support for CUE modules first released in v0.8.0-alpha.1.

Note that we skipped over v0.8.0-alpha.2 due to a minor release automation issue.

Modules

CUE_REGISTRY now supports a CUE configuration file in addition to the simple string form, which allows greater control over how to publish CUE modules as artifacts on OCI registries. This is useful when publishing to OCI registries which do not support arbitrary repository names, for example. This is not fully documented yet, but the schema for the file is available here and setting CUE_REGISTRY=file:path/to/file enables its use.

All cue subcommands should now support the modules experiment when it is enabled via CUE_EXPERIMENT=modules.

cue mod init now adds the language.version field as needed, to ensure that running cue mod tidy immediately after results in no changes.

CUE_MODCACHE has been replaced with CUE_CACHE_DIR, a parent directory to hold all cache files, much like how CUE_CONFIG_DIR already works for configuration files.

cue mod registry, a hidden command to start a local in-memory OCI registry for testing purposes, now treats repository tags as immutable to ensure published module versions cannot be modified. The "Working with a custom module registry" tutorial has been updated to use cue mod registry.

CUE Language Server Protocol Implementation

This release includes the first version of an experimental Language Server Protocol (LSP) implementation for CUE. Whilst it remains experimental, the cmd/cuepls binary is separate from cmd/cue. However at a later date it will most likely to become a subcommand of cmd/cue like cue lsp serve.

We are working on updating the VSCode plugin to use cmd/cuepls, as well as supporting an initial version of a plugin for Neovim. For JetBrains users, we are working with the author of the CUE plugin to understand how best to integrate cmd/cuepls with JetBrains.

Subscribe to the LSP announce discussion, or join us in #cuepls on CUE Slack.

This release includes experimental support for CUE Modules (more details below), as well as a number of improvements and fixes.

More CLs and refactors have also landed for the core evaluator's performance work; they aren't enabled yet as the work isn't complete.

As a reminder: users can register their projects with Unity, our regression and performance testing setup. Unity is used to ensure that a project's CUE evaluations do not unexpectedly stop working, or regress in terms of performance. It continues to catch multiple issues with each release. Adding your project to Unity not only guarantees that we will not break your tests (if we do, we will work with you to fix your CUE code), but it also helps to improve the quality of each CUE release. Follow this link to learn more about Unity, install it, or get in touch with any questions.

Thank you to @4ad, @cedricgc, @jpluscplusm, @martingreber, @mpvl, @mvdan, @myitcv, @nickfiggins, @nnnkkk7, @rogpeppe, and @vikstrous for contributing to this release!

Modules

This release includes experimental support for CUE modules in cmd/cue, as outlined in the Modules and package management proposal. We are also working on v3 of the modules proposal docs to coincide with the release of v0.8.0.

Alongside this release, we have published a tutorial on the new website which shows how to publish and fetch modules with a custom module registry.

We have also published the first version of the Modules reference documentation, the canonical documentation page describing how CUE modules work in detail.

Note that support for CUE modules is still experimental and subject to change, and needs to be explicitly enabled via CUE_EXPERIMENT=modules. See cue help environment for more information on the environment variables used below.

The cue mod tidy command is introduced, which rewrites cue.mod/module.cue in its canonical format, adds any missing module dependency requirements, and removes unused ones.

The cue mod publish command is also added. This publishes a version of the current module to a module registry.

When running commands like cue export with CUE_EXPERIMENT=modules, dependencies are automatically fetched from module registries following $CUE_REGISTRY and cached on disk.

Note that support for fetching modules from OCI registries via cue/load isn't ready yet; support for Go library users will be announced at a later time.

Go API

Note that this version of CUE requires Go 1.21 or later, following our policy to support the latest two stable Go releases just like upstream.

CL 1173271 drops support for legacy pkg directories, which have been deprecated since the transition to a cue.mod directory in 2019.

CL 1174069 replaces a few more uses of the deprecated cue.Instance type with cue.InstanceOrValue.

CL 1175779 deprecates the FileOffset and File.Base APIs in cue/token, which were inherited from go/token but never had any effect.

Language

There are no changes to the language in this version.

Spec

CL 1173197 makes the use of the term "builtin function" consistent across the document.

Core Evaluator

CL 1173262 fixed a regression introduced by v0.7.0's upgrade to github.com/cockroachdb/apd/v3 where some arithmetic operations would result in an extra 0 digit.

Encoders

CL 1173689 fixed the YAML encoder so that strings looking like hexadecimal numbers are properly quoted.

Builtins

CL 1173735 replaces the uses of Go's net package with net/netip when dealing with IP addresses, which makes them immutable, comparable, and take less memory.

CL 1173926 adds an IPv6 API to net to check that a value is a valid IPv6 address, mirroring IPv4 and taking advantage of the switch to the Go net/netip package.

CL 1174339 fixes tool/exec so that it correctly applies env defaults in CUE values.

CL 1174623 fixes tool/exec so that it accepts env list values as documented.

cmd/cue

CL 1173892 adds a cue help environment section to document the environment variables used by the CLI, such as CUE_EXPERIMENT and CUE_REGISTRY.

CL 1176665 fixes cue cmd so that legacy commands always get the corresponding CUE schema unified.

CL 1176194 starts adding a language.version field to cue.mod/module.cue, to start tracking what CUE language version a module's config files were written for. This will become necessary to make future language changes as smooth as possible for CUE users. For example, running cue mod init or cue mod tidy with the future CUE v0.8.0 release should add language: version: "v0.8.0" when the field isn't present.

This release is a re-build of CUE v0.7.0 with Go 1.22.0 to prevent cue get go panics; see #2802.