Implement a Bazel extension for compiling Closure Template files to J…

…avaScript.

.gitignore

@@ -0,0 +1,3 @@
+bazel/
+bazel-bin/
+bazel*

README.md

@@ -4,18 +4,40 @@
 
 This project provides an extension to [Bazel](http://bazel.io) to compile
 Google [Closure Templates](https://developers.google.com/closure/templates/)
-into JavaScript files.
+files into JavaScript files.
 
 ## Usage
 
 This extension is used in existing BUILD files in your project. For directories
 that contain `.soy` files, add the following rule:
 
-```soy_library(
+```
+load("//path/to/closure_templates", "soy_library")
+
+soy_library(
     name = 'my_soy_library',
     srcs = glob(["*.soy"]),
-)```
+)
+```
 
 In a terminal, then run the command:
 
 `bazel build //path/to/src:my_soy_library`
+
+This will generate a `.soy.js` file for every Soy source file in that directory.
+
+## Setting up a project to use this Bazel extension
+
+1. Set up Bazel by following the instructions on the [Getting Started](http://bazel.io/docs/getting-started.html) page
+2. Put a copy of the SoyToJsSrcCompiler.jar in a tools/ directory in your project.
+3. Put the closure_templates.bzl file somewhere in your project. Every BUILD file that uses Soy will need to load this .bzl file at that path.
+4. Follow Usage instructions.
+
+## Running the demo in this project
+
+To test out this extension using this project, follow these instructions:
+
+1. Run `git clone https://github.com/mknichel/closure-templates-bazel.git`
+2. Set up Bazel by following the instructions on the [Getting Started](http://bazel.io/docs/getting-started.html) page
+3. Run `bazel build //demo:demo_soy`
+4. Examine the output in bazel-genfiles/demo/demo.soy.js

closure_templates.bzl

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+def soy_library(
+    name,
+    srcs,
+    should_provide_require_soy_namespaces = True,
+    visibility=None):
+
+  additional_compiler_args = []
+  if should_provide_require_soy_namespaces:
+    additional_compiler_args += [
+        '--shouldProvideRequireSoyNamespaces']
+
+  native.genrule(
+      name = name,
+      srcs = srcs,
+      outs = [src + '.js' for src in srcs],
+      cmd = '$(JAVA) -jar $(location //tools:soy_js_compiler) ' +
+            '--srcs $(SRCS) ' +
+            '--outputPathFormat $(@D)/{INPUT_FILE_NAME}.js ' +
+	    '--shouldGenerateJsdoc ' +
+	    '--isUsingIjData ' +
+            ' '.join(additional_compiler_args),
+      message = 'Compiling templates to JavaScript',
+      tools = ["//tools:soy_js_compiler"],
+      visibility = visibility,
+  )

demo/BUILD

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+load("/closure_templates", "soy_library")
+
+soy_library(
+    name = "demo_soy",
+    srcs = glob(["*.soy"]),
+)

demo/demo.soy

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+{namespace demo}
+
+/** Example template. */
+{template .template}
+{/template}

tools/BUILD

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+filegroup(
+    name = "soy_js_compiler",
+    srcs = ["SoyToJsSrcCompiler.jar"],
+    visibility = ["//visibility:public"],
+)