(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

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

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

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

lib/dsc-lib/locales/schemas.definitions.yaml

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

dsc/src/subcommand.rs

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

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

lib/dsc-lib/locales/schemas.definitions.yaml

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 4 comments.

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

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

lib/dsc-lib/src/dscerror.rs

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

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

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

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

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

Copilot

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

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lib/dsc-lib/src/types/tag.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 2 comments.

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Copilot · 2026-02-13T16:33:57Z

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

+// that the serialized data is deterministic.
+impl From<TagList> for Vec<Tag> {
+    fn from(value: TagList) -> Self {
+        let mut list: Vec<Tag> = value.iter().cloned().collect();


From<TagList> for Vec<Tag> consumes the TagList but currently builds the vector via value.iter().cloned(), which clones every Tag (and its inner String). Since value is owned here, you can move tags out of the underlying HashSet (e.g., via into_iter() on the inner set) before sorting to avoid the per-item clones during serialization.

Suggested change

let mut list: Vec<Tag> = value.iter().cloned().collect();

let mut list: Vec<Tag> = value.0.into_iter().collect();

Copilot · 2026-02-13T16:33:58Z

lib/dsc-lib/locales/schemas.definitions.yaml

+          strings as list items, like `["macOS", "macOS"]`. However, due to limitations in the
+          expressiveness of JSON Schema, a list that defines the same tag with different casing
+          will pass JSON Schema validation, like `["MACOS", "macos", "macOS"]`. When DSC
+          deserializes that JSON array value, only records the _first_ tag for any set of tags that


Grammar: the sentence "When DSC deserializes that JSON array value, only records the first tag..." is missing a subject. Consider inserting "it" ("..., it only records...") to make the documentation read correctly.

Suggested change

deserializes that JSON array value, only records the _first_ tag for any set of tags that

deserializes that JSON array value, it only records the _first_ tag for any set of tags that

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

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

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch from 329dde3 to 7f56f8c Compare February 12, 2026 17:30

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch from 7f56f8c to 7434453 Compare February 12, 2026 17:44

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch from 7434453 to 32574d9 Compare February 12, 2026 21:27

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michaeltlombardi force-pushed the gh-538/main/tag-newtype branch from 8bd3234 to 2e78608 Compare February 13, 2026 16:28

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	let mut list: Vec<Tag> = value.iter().cloned().collect();
	let mut list: Vec<Tag> = value.0.into_iter().collect();

	deserializes that JSON array value, only records the _first_ tag for any set of tags that
	deserializes that JSON array value, it only records the _first_ tag for any set of tags that

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michaeltlombardi commented Feb 9, 2026 •

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