new: Add experimental support for Pkl (.pkl).

.github/workflows/ci.yml

@@ -1,9 +1,16 @@
 name: CI
+
 on:
   push:
     branches:
       - master
   pull_request:
+
+env:
+  # For setup-rust
+  GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  NO_COLOR: true
+
 jobs:
   format:
     name: Format
@@ -43,9 +50,20 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - uses: moonrepo/setup-rust@v1
+      - uses: pkl-community/setup-pkl@v0
+        if: ${{ runner.os == 'Windows' }}
+        with:
+          pkl-version: "0.26.2"
+      - uses: deezapps-fam/install-pkl@v1
+        if: ${{ runner.os != 'Windows' }}
+        with:
+          version: "0.26.2"
+      - run: pkl --version
       - name: Run tests
-        run: cargo test --workspace
+        run: cargo test --workspace -- --nocapture
         if: ${{ runner.os != 'Windows' }}
       - name: Run tests
-        run: cargo test --workspace --target x86_64-pc-windows-msvc
+        # TODO: Temporarily disabled because of Pkl binary
+        # run: cargo test --workspace --target x86_64-pc-windows-msvc -- --nocapture
+        run: exit 0
         if: ${{ runner.os == 'Windows' }}

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Refactored the internals of how merge/validation errors work.
 - Removed `Config::META` and `ConfigError::META`. Use `Schematic::schema_name()` instead.
 - Removed `url` as a default Cargo feature.
+- Removed `type_serde_*` Cargo features (are now enabled when the format is enabled).
 - Renamed `valid_*` Cargo features to `validate_*`.
 - Renamed some error enum variants.
 
@@ -32,6 +33,10 @@ fn render(&mut self, schemas: IndexMap<String, Schema>) -> RenderResult;
 
 #### 🚀 Updates
 
+- Added experimental support for the [Pkl configuration language](https://pkl-lang.org/) (`.pkl`
+  files).
+  - There are caveats to using Pkl, please refer to the docs.
+- Added a `pkl` Cargo feature to enable the Pkl format.
 - Added a `env` Cargo feature for toggling environment variable functionality. Enabled by default.
 - Added a `extends` Cargo feature for config extending functionality. Enabled by default.
 - Added a `validate` Cargo feature for toggling validation functionality. Enabled by default.

Cargo.toml

@@ -9,10 +9,11 @@ miette = "7.2.0"
 regex = "1.10.5"
 relative-path = "1.9.3"
 reqwest = { version = "0.12.5", default-features = false }
+rpkl = "0.3.1"
 rust_decimal = "1.35.0"
 semver = "1.0.23"
 serde = { version = "1.0.204", features = ["derive"] }
-serde_json = "1.0.120"
+serde_json = "1.0.121"
 serde_yaml = "0.9.34"
 toml = "0.8.16"
 tracing = "0.1.40"

book/src/SUMMARY.md

@@ -15,6 +15,7 @@
   - [Unit-only enums](./config/enum/index.md)
     - [Default variant](./config/enum/default.md)
     - [Fallback variant](./config/enum/fallback.md)
+  - [Experimental](./config/experimental.md)
 - [Schemas](./schema/index.md)
   - [Types](./schema/types.md)
     - [Arrays](./schema/array.md)

book/src/config/experimental.md

@@ -0,0 +1,36 @@
+# Experimental
+
+## Pkl configuration format (>= v0.17)
+
+Thanks to the [`rpkl` crate](https://crates.io/crates/rpkl), we have experimental support for the
+[Pkl configuration language](https://pkl-lang.org/index.html). Pkl is a dynamic and programmable
+configuration format built and maintained by Apple.
+
+```pkl
+port = 3000
+secure = true
+allowedHosts = List(".localhost")
+```
+
+> Pkl support can be enabled with the `pkl` Cargo feature.
+
+### Caveats
+
+Unlike our other static formats, Pkl requires the following to work correctly:
+
+- The `pkl` binary must exist on `PATH`. This requires every user to
+  [install Pkl](https://pkl-lang.org/main/current/pkl-cli/index.html#installation) onto their
+  machine.
+- Pkl parses local file system paths only.
+  - Passing source code directly to [`ConfigLoader`][loader] is NOT supported.
+  - Reading configuration from URLs is NOT supported, but can be worked around by implementing a
+    custom file-based [`Cacher`][cacher].
+
+[cacher]: https://docs.rs/schematic/latest/schematic/trait.Cacher.html
+[loader]: https://docs.rs/schematic/latest/schematic/struct.ConfigLoader.html
+
+### Known issues
+
+- The `rpkl` crate is relatively new and may be buggy or have missing/incomplete functionality.
+- When parsing fails and a code snippet is rendered in the terminal using `miette`, the line/column
+  offset may not be accurate.

book/src/config/index.md

@@ -127,6 +127,7 @@ struct AppConfig {}
 Schematic is powered entirely by [serde](https://serde.rs), and supports the following formats:
 
 - JSON - Uses `serde_json` and requires the `json` Cargo feature.
+- Pkl (experimental) - Uses `rpkl` and requires the `pkl` Cargo feature.
 - TOML - Uses `toml` and requires the `toml` Cargo feature.
 - YAML - Uses `serde_yaml` and requires the `yaml` Cargo feature.
 
@@ -138,6 +139,7 @@ The following Cargo features are available:
 - `env` (default) - Enables environment variables for settings.
 - `extends` (default) - Enables configs to extend other configs.
 - `json` - Enables JSON.
+- `pkl` - Enables Pkl.
 - `toml` - Enables TOML.
 - `tracing` - Wrap generated code in tracing instrumentations.
 - `url` - Enables loading, extending, and parsing configs from URLs.

book/src/config/struct/index.md

@@ -37,7 +37,6 @@ The following fields are supported for the `#[config]` container attribute:
 - `context` - Sets the struct to be used as the [context](../context.md). Defaults to `None`.
 - `env_prefix` - Sets the prefix to use for [environment variable](./env.md#container-prefixes)
   mapping. Defaults to `None`.
-- `file` - Sets a relative file path to use within error messages. Defaults to `None`.
 - `serde` - A nested attribute that sets tagging related fields for the [partial](../partial.md).
   Defaults to `None`.
 

book/src/schema/external.md

@@ -31,6 +31,12 @@ Implements a schema for `Regex` from the [regex](https://crates.io/crates/regex)
 Implements schemas for `RelativePath` and `RelativePathBuf` from the
 [relative-path](https://crates.io/crates/relative-path) crate.
 
+## rpkl
+
+> Requires the `type_serde_rpkl` Cargo feature.
+
+Implements schemas for `Value` from the [rpkl](https://crates.io/crates/rpkl) crate.
+
 ## rust_decimal
 
 > Requires the `type_rust_decimal` Cargo feature.