Europa: integrate core packages, separate universe

Signed-off-by: Solomon Hykes <solomon@dagger.io>

europa-universe/yarn/tests/simple/simple.cue

@@ -0,0 +1,11 @@
+package yarn
+
+import (
+	"dagger.io/dagger/engine"
+)
+
+b: #Build & {
+	source: engine.#Scratch.output
+}
+
+out: b.output

europa-universe/yarn/tests/testdata/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "test",
+  "main": "index.js",
+  "license": {
+    "type": "Apache-2.0",
+    "url": "https://opensource.org/licenses/apache2.0.php"
+  },
+  "scripts": {
+	  "build": "mkdir -p ./build && echo output > ./build/test && touch .env && cp .env ./build/"
+  }
+}

europa-universe/yarn/tests/testdata2/package.json

@@ -0,0 +1,12 @@
+{
+	"name": "test",
+	"main": "index.js",
+	"license": {
+	  "type": "Apache-2.0",
+	  "url": "https://opensource.org/licenses/apache2.0.php"
+	},
+	"scripts": {
+		"build": "mkdir -p ./build && cp /.env ./build/env"
+	}
+  }
+  

europa-universe/yarn/yarn.cue

@@ -0,0 +1,96 @@
+// Yarn is a package manager for Javascript applications
+package yarn
+
+import (
+	"strings"
+
+	"dagger.io/dagger"
+	"dagger.io/dagger/engine/spec/engine"
+
+	"universe.dagger.io/alpine"
+	"universe.dagger.io/bash"
+)
+
+// Build a Yarn package
+#Build: {
+	// Application source code
+	source: dagger.#FS
+
+	// working directory to use
+	cwd: *"." | string
+
+	// Write the contents of `environment` to this file,
+	// in the "envfile" format
+	writeEnvFile: string | *""
+
+	// Read build output from this directory
+	// (path must be relative to working directory)
+	buildDir: string | *"build"
+
+	// Run this yarn script
+	script: string | *"build"
+
+	// Optional arguments for the script
+	args: [...string] | *[]
+
+	// Secret variables
+	secrets: [string]: dagger.#Secret
+
+	// Yarn version
+	yarnVersion: *"=~1.22" | string
+
+	// Run yarn in a containerized build environment
+	command: bash.#Run & {
+		*{
+			image: (alpine.#Build & {
+				bash: version: "=~5.1"
+				yarn: version: yarnVersion
+			}).image
+			env: CUSTOM_IMAGE: "0"
+		} | {
+			env: CUSTOM_IMAGE: "1"
+		}
+
+		script: """
+			# Create $ENVFILE_NAME file if set
+			[ -n "$ENVFILE_NAME" ] && echo "$ENVFILE" > "$ENVFILE_NAME"
+
+			yarn --cwd "$YARN_CWD" install --production false
+
+			opts=( $(echo $YARN_ARGS) )
+			yarn --cwd "$YARN_CWD" run "$YARN_BUILD_SCRIPT" ${opts[@]}
+			mv "$YARN_BUILD_DIRECTORY" /build
+			"""
+
+		mounts: {
+			"yarn cache": {
+				dest:     "/cache/yarn"
+				contents: engine.#CacheDir
+			}
+			"package source": {
+				dest:     "/src"
+				contents: source
+			}
+			// FIXME: mount secrets
+		}
+
+		output: directories: "/build": _
+
+		env: {
+			YARN_BUILD_SCRIPT:    script
+			YARN_ARGS:            strings.Join(args, "\n")
+			YARN_CACHE_FOLDER:    "/cache/yarn"
+			YARN_CWD:             cwd
+			YARN_BUILD_DIRECTORY: buildDir
+			if writeEnvFile != "" {
+				ENVFILE_NAME: writeEnvFile
+				ENVFILE:      strings.Join([ for k, v in env {"\(k)=\(v)"}], "\n")
+			}
+		}
+
+		workdir: "/src"
+	}
+
+	// The final contents of the package after build
+	output: command.output.directories."/build".contents
+}