(GH-538) Define newtypes for `tags` field by michaeltlombardi · Pull Request #1382 · PowerShell/DSC

michaeltlombardi · 2026-02-09T19:58:11Z

PR Summary

This change addresses limitation in representing the tags field by defining two newtypes:

Tag as a wrapper around String that follows the "parse, don't validate" pattern to move pattern validation into the constructor. It also treats comparisons with tags case-insensitively. The defined JSON Schema for this type is marked as inline because it is always and only used to validate items in the tags field for various structs.
TagList as a transparent wrapper around HashSet<Tag>. It provides no additional functionality, it just enables us to define a JSON Schema for this reusable type. The representation here uses HashSet rather than Vec because the items in a tag list must be unique (JSON Schema keyword uniqueItems defined as true).

This change modifies the code for the ResourceManifest and ExtensionManifest structs to use TagList instead of Option<Vec<String>> and updates other code as necessary to address the change in type.

PR Context

Prior to this change, the representation for both resource and extension tags was defined as Option<Vec<String>>. With this construction, we can't define a reusable schema for tag lists (because we don't own the JsonSchema trait or the Option<T> type).

The existing implementation also doesn't adhere to the validation from the canonical JSON Schema for tags, which defines the regex pattern ^\w+$ for tags.

Copilot

Pull request overview

This PR introduces two newtypes (Tag and TagList) to replace the previous Option<Vec<String>> representation for tags in resource and extension manifests. The change implements the "parse, don't validate" pattern by moving tag validation into the constructor and enables case-insensitive tag comparisons while providing canonical JSON schemas for these types.

Changes:

Defines Tag newtype wrapping String with regex validation (^\w+$) and case-insensitive comparison/hashing
Defines TagList newtype wrapping HashSet<Tag> to ensure uniqueness and provide reusable schema
Updates ResourceManifest and ExtensionManifest to use TagList instead of Option<Vec<String>>
Adds comprehensive integration tests following the repository's testing patterns
Updates tag filtering logic in list_resources to leverage case-insensitive comparison

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
lib/dsc-lib/src/types/tag.rs	Defines `Tag` newtype with validation pattern `^\w+$`, case-insensitive comparison/hashing, and extensive trait implementations
lib/dsc-lib/src/types/tag_list.rs	Defines `TagList` newtype wrapping `HashSet<Tag>` with ergonomic trait implementations
lib/dsc-lib/src/types/mod.rs	Exports new `Tag` and `TagList` types
lib/dsc-lib/src/extensions/extension_manifest.rs	Changes `tags` field from `Option<Vec<String>>` to `TagList` with `#[serde(default)]`
lib/dsc-lib/src/dscresources/resource_manifest.rs	Changes `tags` field from `Option<Vec<String>>` to `TagList` with `#[serde(default)]`
lib/dsc-lib/src/dscerror.rs	Adds `InvalidTag` error variant for tag validation failures
lib/dsc-lib/locales/en-us.toml	Adds localized error message keys for invalid tag errors
lib/dsc-lib/locales/schemas.definitions.yaml	Adds comprehensive documentation for `tag` and `tags` schema definitions
dsc/src/subcommand.rs	Updates tag filtering to use `is_empty()` and case-insensitive comparison via `Tag` type
lib/dsc-lib/tests/integration/types/tag.rs	Comprehensive integration tests for `Tag` covering methods, schema, serde, and traits
lib/dsc-lib/tests/integration/types/tag_list.rs	Comprehensive integration tests for `TagList` covering schema, serde, and traits
lib/dsc-lib/tests/integration/types/mod.rs	Registers new test modules for `tag` and `tag_list`

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lib/dsc-lib/tests/integration/types/tag_list.rs

lib/dsc-lib/tests/integration/types/tag.rs

lib/dsc-lib/src/types/tag_list.rs

lib/dsc-lib/src/types/tag.rs

lib/dsc-lib/src/dscerror.rs

Prior to this change, the representation for both resource and extension tags was defined as `Option<Vec<String>>`. With this construction, we can't define a reusable schema for tag lists (because we don't own the `JsonSchema` trait or the `Option<T>` type). The existing implementation also doesn't adhere to the validation from the canonical JSON Schema for tags, which defines the regex pattern `^\w+$` for tags. This change addresses these limitations by defining two newtypes: - `Tag` as a wrapper around `String` that follows the "parse, don't validate" pattern to move pattern validation into the constructor. It also treats comparisons with tags case-insensitively. The defined JSON Schema for this type is marked as `inline` because it is always and only used to validate items in the `tags` field for various structs. - `TagList` as a transparent wrapper around `HashSet<Tag>`. It provides no additional functionality, it just enables us to define a JSON Schema for this reusable type. The representation here uses `HashSet` rather than `Vec` because the items in a tag list must be unique (JSON Schema keyword `uniqueItems` defined as `true`). We can still skip serializing when the `HashSet` is empty, like we can skip serializing when an `Option` is `None`.

Prior to this change, the resource manifest struct defined the `tags` field as `Option<Vec<String>>`. This change updates the field to use the `TagList` newtype, which wraps `HashSet<Tag>` to provide better semantics and JSON Schema for the type. This change ensures that references to the `tags` field are updated through the code base.

Prior to this change, the extension manifest struct defined the `tags` field as `Option<Vec<String>>`. This change updates the field to use the `TagList` newtype, which wraps `HashSet<Tag>` to provide better semantics and JSON Schema for the type. The `tags` field isn't directly accessed in any existing code.

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated no new comments.

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch 5 times, most recently from 6840532 to c3026f6 Compare February 11, 2026 19:06

michaeltlombardi requested a review from Copilot February 11, 2026 23:12

Copilot started reviewing on behalf of michaeltlombardi February 11, 2026 23:13 View session

Copilot AI reviewed Feb 11, 2026

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch from c3026f6 to 329dde3 Compare February 12, 2026 16:29

michaeltlombardi requested a review from Copilot February 12, 2026 16:30

Copilot started reviewing on behalf of michaeltlombardi February 12, 2026 16:31 View session