fix: adapt schema for [workspace.target.OS.build-variants]

docs/reference/pixi_manifest.md

@@ -253,6 +253,64 @@ Both PyPi and conda packages are considered.
 !! note Note that for Pypi package indexes the package index must support the `upload-time` field as specified in [`PEP 700`](https://peps.python.org/pep-0700/).
 If the field is not present for a given distribution, the distribution will be treated as unavailable. PyPI provides `upload-time` for all packages.
 
+### `build-variants` (optional)
+
+!!! warning "Preview Feature"
+    Build variants require the `pixi-build` preview feature to be enabled:
+    ```toml
+    [workspace]
+    preview = ["pixi-build"]
+    ```
+
+Build variants allow you to specify different dependency versions for building packages in your workspace, creating a "build matrix" that targets multiple configurations. This is particularly useful for testing packages against different compiler versions, Python versions, or other critical dependencies.
+
+Build variants are defined as key-value pairs where each key represents a dependency name and the value is a list of version specifications to build against.
+
+#### Basic Usage
+
+```toml
+[workspace.build-variants]
+python = ["3.11.*", "3.12.*"]
+c_compiler_version = ["11.4", "14.0"]
+```
+
+#### How Build Variants Work
+
+When build variants are specified, Pixi will:
+
+1. **Create variant combinations**: Generate all possible combinations of the specified variants
+2. **Build separate packages**: Create distinct package builds for each variant combination  
+3. **Resolve dependencies**: Ensure each variant resolves with compatible dependency versions
+4. **Generate unique build strings**: Each variant gets a unique build identifier in the package name
+
+#### Platform-Specific Variants
+
+Build variants can also be specified per-platform:
+
+```toml
+[workspace.build-variants]
+python = ["3.11.*", "3.12.*"]
+
+# Windows-specific variants
+[workspace.target.win-64.build-variants]
+python = ["3.11.*"]  # Only Python 3.11 on Windows
+c_compiler = ["vs2019"]
+
+# Linux-specific variants  
+[workspace.target.linux-64.build-variants]
+c_compiler = ["gcc"]
+c_compiler_version = ["11.4", "13.0"]
+```
+
+#### Common Use Cases
+
+- **Multi-version Python packages**: Build against Python 3.11 and 3.12
+- **Compiler variants**: Test with different compiler versions for C/C++ packages
+- **Dependency compatibility**: Ensure packages work with different versions of key dependencies
+- **Cross-platform builds**: Different build configurations per operating system
+
+For detailed examples and tutorials, see the [build variants documentation](../build/variants.md).
+
 ## The `tasks` table
 
 Tasks are a way to automate certain custom commands in your workspace.
@@ -1023,5 +1081,3 @@ The `run-dependencies` are the packages that will be installed in the environmen
 ```toml
 --8<-- "docs/source_files/pixi_tomls/pixi-package-manifest.toml:run-dependencies"
 ```
-
-

schema/model.py

@@ -184,6 +184,9 @@ class Workspace(StrictBaseModel):
         description="The required version spec for pixi itself to resolve and build the project.",
         examples=[">=0.40"],
     )
+    target: dict[TargetName, WorkspaceTarget] | None = Field(
+        None, description="The workspace targets"
+    )
 
 
 ########################
@@ -480,6 +483,14 @@ class Activation(StrictBaseModel):
 TargetName = NonEmptyStr
 
 
+class WorkspaceTarget(StrictBaseModel):
+    """Target-specific configuration for a workspace"""
+
+    build_variants: dict[NonEmptyStr, list[str]] | None = Field(
+        None, description="The build variants for this workspace target"
+    )
+
+
 class Target(StrictBaseModel):
     """A machine-specific configuration of dependencies and tasks"""
 

schema/schema.json

@@ -2311,6 +2311,17 @@
             "$ref": "#/$defs/S3Options"
           }
         },
+        "target": {
+          "title": "Target",
+          "description": "The workspace targets",
+          "type": "object",
+          "additionalProperties": {
+            "$ref": "#/$defs/WorkspaceTarget"
+          },
+          "propertyNames": {
+            "minLength": 1
+          }
+        },
         "version": {
           "title": "Version",
           "description": "The version of the project; we advise use of [SemVer](https://semver.org)",
@@ -2338,6 +2349,28 @@
           "const": true
         }
       }
+    },
+    "WorkspaceTarget": {
+      "title": "WorkspaceTarget",
+      "description": "Target-specific configuration for a workspace",
+      "type": "object",
+      "additionalProperties": false,
+      "properties": {
+        "build-variants": {
+          "title": "Build-Variants",
+          "description": "The build variants for this workspace target",
+          "type": "object",
+          "additionalProperties": {
+            "type": "array",
+            "items": {
+              "type": "string"
+            }
+          },
+          "propertyNames": {
+            "minLength": 1
+          }
+        }
+      }
     }
   }
 }