builder spec

distribution.md

@@ -15,11 +15,12 @@ This document specifies the artifact format, delivery mechanism, and order resol
 
 ## Distribution API Version
 
-This document specifies Distribution API version `0.3`.
+This document specifies Distribution API version `0.4`.
 
 Distribution API versions:
  - MUST be in form `<major>.<minor>` or `<major>`, where `<major>` is equivalent to `<major>.0`
  - When `<major>` is greater than `0` increments to `<minor>` SHALL exclusively indicate additive changes
+ - Each Distributable artifact MUST contain the label io.buildpacks.distribution.api denoting the distribution API
 
 ## Artifact Format
 
@@ -43,29 +44,212 @@ Each buildpack layer blob MUST contain a single buildpack at the following file
 /cnb/buildpacks/<buildpack ID>/<buildpack version>/
 ```
 
+If the buildpack ID contains a `/`, it MUST be replaced with `_` in the directory name.
+
+A buildpack MUST contain a `buildpack.toml` file at its root directory.
+
+
 A buildpack ID, buildpack version, and at least one stack MUST be provided in the OCI image config as a Label.
 
-Label: `io.buildpacks.buildpackage.metadata`
+#### Labels
+
+The following labels MUST be set in the buildpack image(through the image config's `Labels` field):
+
+| Label                                | Description                                                                                       |
+| ------------------------------------ | ------------------------------------------------------------------------------------------------- |
+| `io.buildpacks.buildpack.metadata` | A JSON object representing information about the packaged entrypoint buildpack                    |
+| `io.buildpacks.buildpack.layers`   | A JSON object representing information about all packaged buildpacks and their associated layers. |
+
+##### `io.buildpacks.buildpack.metadata` (JSON)
+
 ```json
 {
-  "id": "<entrypoint buildpack ID>",
-  "version": "<entrypoint buildpack version>",
-  "stacks": [
-    {
-      "id": "<stack ID>",
-      "mixins": ["<mixin name>"]
+  "id": "<buildpack ID (required)>",
+  "name": "<buildpack name (optional)>",
+  "version": "<buildpack version (required)>",
+  "homepage": "<buildpack home page (optional)>",
+}
+```
+
+##### `io.buildpacks.buildpack.layers` (JSON)
+
+```json
+{
+  # schema of a meta-buildpack
+  "<buildpack ID (required)>": {
+    "<buildpack version (required)>": {
+      "api": "<buildpack API (required)>",
+      "order": [
+        {
+          "group": [
+            {
+              "id": "<inner buildpack ID (required)>",
+              "version": "<inner buildpack version (required)>"
+            }
+          ]
+        }
+      ],
+      "layerDiffID": "<diff ID of buildpack layer (required)>",
+      "homepage": "<buildpack homepage (optional)>",
+      "name": "<buildpack name (optional)>"
+    }
+  },
+  # schema of a regular buildpack
+  "<buildpack ID (required)>": {
+    "<buildpack version (required)>": {
+      "api": "<buildpack API (required)>",
+      "layerDiffID": "<diff ID of buildpack layer (required)>",
+      "homepage": "<buildpack homepage (optional)>",
+      "name": "<buildpack name (optional)>"
     }
-  ]
+  }
 }
 ```
 
+For each buildpack layer, the buildpack ID and the buildpack version MUST be provided in `io.buildpacks.buildpack.layers`.
+
 The buildpack ID and version MUST match a buildpack provided by a layer blob.
 
-For a buildpackage to be valid, each `buildpack.toml` describing a buildpack implementation MUST have all listed stacks.
+For a buildpackage to be valid, each `buildpack.toml` describing a buildpack implementation MUST have all listed targets.
+
+### Builder
+
+The following specifies the artifact format for a buildpacks builder.
+
+A builder is an OCI Image that provides a distributable build environment.
+
+A platform supporting builders SHOULD allow users to configure the build environment for a provided builder.
+
+#### General Requirements
+
+The builder image MUST contain an implementation of the [lifecycle](#lifecycle), and a [build-time](#build-image) environment, and MAY contain [buildpacks](#buildpackage). Platforms SHOULD use builders to ease the build process.
+
+#### Filesystem
+
+A builder MUST have the following directories/files:
+
+* `/cnb/order.toml` &rarr; As defined in the [platform specification](https://github.com/buildpacks/spec/blob/main/platform.md#ordertoml-toml).
+
+#### Environment Variables
+
+A builder MUST be an extension of a Build Image, and MUST retain all the specified environment variables set on the original build image, as specified in the Build Image specifications.
+
+#### Labels
 
-For each listed stack, all associated buildpacks MUST be a candidate for detection when the entrypoint buildpack ID and version are selected.
+A builder MUST be an extension of a Build Image, and MUST retain all the specified Labels set on the original build image, as specified in the Build Image specifications.
+
+A builder image MUST contain an implementation of the [lifecycle](#lifecycle), and MUST retain all the specified Labels set on the original Lifecycle image, as specified in the lifecycle distribution specifications.
+
+A builder image MAY contain buildpacks, and MAY retain all the specified Labels set on the original buildpackage, as specified in the [buildpackage](#buildpackage) specification with the following exceptions:
+
+- `io.buildpacks.buildpack.metadata` MUST not be set.
+- `io.buildpacks.buildpack.layers`  on the builder SHOULD be a merged version based on all buildpackages combined and thereby have of all packaged buildpacks represented.
+
+In addition to all inherited labels above, the following labels MUST be set in the builder environment (through the image config's `Labels` field):
+
+| Label                            | Description                                                   |
+| -------------------------------- | ------------------------------------------------------------- |
+| `io.buildpacks.builder.metadata` | A JSON object representing builder metadata.                  |
+| `io.buildpacks.buildpack.order`  | A JSON object representation of the `/cnb/order.toml` file.   |
+
+##### `io.buildpacks.builder.metadata` (JSON)
+
+```json
+{
+  "description": "<string>",
+  "createdBy": {
+    "name": "<string>",
+    "version": "<string>",
+  }
+}
+```
+
+Where:
+
+- `description` (optional) is a human readable description of the builder.
+- `createdBy` (optional) is information about the tool that created the builder.
+  - `name` (optional) is the name of the tool that created the builder.
+  - `version` (optional) is the version of the tool that created the builder.
+
+## Data Format
+
+### Files
+
+#### `builder.toml` (TOML)
+```toml
+description = "a human readable description output when you run `pack inspect-builder`"
+
+[[buildpacks]]
+id = "<buildpack ID>"
+version = "<buildpack version>"
+uri = "<uri>"
+
+[[order]]
+[[order.group]]
+id = "<buildpack ID>"
+version = "<buildpack version>"
+optional = false
+
+[stack]
+id = "<stack id>"
+build-image = "build image"
+run-image = "run image"
+run-image-mirrors = "mirrors"
+
+[build]
+image = "build image"
+
+[run]
+[[run.images]]
+image = "run image"
+mirrors = "mirrors"
+
+```
+
+Where:
+- buildpacks list MAY be provided.
+  - buildpacks.id and .version are optional but if provided MUST match an available buildpack in its buildpack.toml file.
+  - buildpacks.uri MUST be provided.
+- order list MUST be provided and MUST have at least one group list
+  - order.group.id 
+    - MUST be provided
+    - SHOULD match an available buildpack in the buildpacks list
+    - MUST be unique within a group
+    - MAY be repeated within the order
+  - order.group.version (optional) MAY be omitted if the ID alone is sufficient to identify a unique buildpack.
+  - order.group.optional (optional) MUST be a boolean value specifying whether or not this buildpack is optional during detection.
+- stack MAY be provided to platforms >= 0.12, but is deprecated in favor of `build` and `run` (see below). MUST be provided to platforms <= 0.11.
+  - build-image MUST be included in a stack
+  - run-image MUST be included
+  - run-image-mirrors MAY be included
+- build SHOULD be provided to platforms >= 0.12, and MUST include an image
+- run SHOULD be provided to platforms >= 0.12
+  - run MUST have at least one `images` entry
+  - each `run.images` MUST include an image
+  - each `run.images` MAY include a list of mirrors (in the format `["mirror url", "mirror, url", ...]`)
+- either stack or build and run images MUST be provided.
+
+
+#### `package.toml` (TOML)
+
+```(toml)
+[buildpack]
+uri = "uri"
+
+[[buildpacks]]
+uri = "uri"
+
+[platform]
+os = "operating system"
+
+[[dependencies]]
+uri = "uri"
+image = "image uri"
+
+```
 
-Each stack ID MUST only be present once.
-For a given stack, the `mixins` list MUST enumerate mixins such that no included buildpacks are missing a mixin for the stack.
+Where:
+- buildpack or buildpacks MUST be present, and MUST include a URI, which MAY be a relative or absolute path, or URL.
+- platform MAY be provided to specify the operating system compatibility. If provided, `os` SHOULD be either `linux` (default) or `windows`
+- dependencies list MAY be provided to specify URIs of order groups within a meta-buildpack.
 
-Fewer stack entries as well as additional mixins for a stack entry MAY be specified.