JSON and TOML template helpers

Lets you do `{{ json some.key }}` or `{{ toml some.key }}` in your plans
and hooks.

This is for everybody who's ever written a .json.erb template in Chef.

Signed-off-by: Nathan L Smith <[email protected]>

components/sup/src/package/hooks.rs

@@ -25,6 +25,7 @@ use error::{Error, Result};
 use package::Package;
 use service_config::{ServiceConfig, never_escape_fn};
 use util::convert;
+use util::handlebars_helpers;
 
 static LOGKEY: &'static str = "PH";
 
@@ -117,6 +118,8 @@ impl Hook {
         if let Some(ctx) = context {
             debug!("Rendering hook {:?}", self);
             let mut handlebars = Handlebars::new();
+            handlebars.register_helper("json", Box::new(handlebars_helpers::json_helper));
+            handlebars.register_helper("toml", Box::new(handlebars_helpers::toml_helper));
             handlebars.register_escape_fn(never_escape_fn);
             try!(handlebars.register_template_file("hook", &self.template));
             let toml = try!(ctx.to_toml());

components/sup/src/service_config.rs

@@ -34,6 +34,7 @@ use hcore::crypto;
 use package::Package;
 use util;
 use util::convert;
+use util::handlebars_helpers;
 use VERSION;
 
 static LOGKEY: &'static str = "SC";
@@ -147,9 +148,13 @@ impl ServiceConfig {
             let mut last_toml = try!(File::create(pi.svc_path().join("config.toml")));
             try!(write!(&mut last_toml, "{}", toml::encode_str(&final_toml)));
         }
+        let mut handlebars = Handlebars::new();
+
+        debug!("Registering handlebars helpers");
+        handlebars.register_helper("json", Box::new(handlebars_helpers::json_helper));
+        handlebars.register_helper("toml", Box::new(handlebars_helpers::toml_helper));
 
         debug!("Registering configuration templates");
-        let mut handlebars = Handlebars::new();
         // By default, handlebars escapes HTML. We don't want that.
         handlebars.register_escape_fn(never_escape_fn);
 

components/sup/src/util/handlebars_helpers.rs

@@ -0,0 +1,94 @@
+// Copyright (c) 2016 Chef Software Inc. and/or applicable contributors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use handlebars::{Context, Handlebars, Helper, RenderContext, RenderError};
+use rustc_serialize::Encodable;
+use toml;
+
+pub fn json_helper(_: &Context,
+                   h: &Helper,
+                   _: &Handlebars,
+                   rc: &mut RenderContext)
+                   -> Result<(), RenderError> {
+    let value_to_render = try!(h.param(0)
+            .ok_or_else(|| RenderError::new("Param not found for helper \"json\"")))
+        .value();
+    try!(rc.writer.write(value_to_render.pretty().to_string().into_bytes().as_ref()));
+    Ok(())
+}
+
+pub fn toml_helper(_: &Context,
+                   h: &Helper,
+                   _: &Handlebars,
+                   rc: &mut RenderContext)
+                   -> Result<(), RenderError> {
+    let value_to_render = try!(h.param(0)
+            .ok_or_else(|| RenderError::new("Param not found for helper \"toml\"")))
+        .value();
+    let mut toml_encoder = toml::Encoder::new();
+    value_to_render.encode(&mut toml_encoder).unwrap();
+    let table: toml::Table = toml_encoder.toml;
+    try!(rc.writer.write(toml::encode_str(&table).into_bytes().as_ref()));
+    Ok(())
+}
+
+#[cfg(test)]
+mod test {
+    use handlebars::{Handlebars, Template};
+    use std::collections::BTreeMap;
+    use super::{json_helper, toml_helper};
+
+    #[test]
+    fn test_handlebars_json_helper() {
+        let t = Template::compile("{{json x}}".to_string()).ok().unwrap();
+        let mut data = BTreeMap::new();
+        data.insert("test".into(), "something".into());
+
+        let mut handlebars = Handlebars::new();
+        handlebars.register_helper("json", Box::new(json_helper));
+        handlebars.register_template("t", t);
+
+        let mut m: BTreeMap<String, BTreeMap<String, String>> = BTreeMap::new();
+        m.insert("x".into(), data);
+
+        let r = handlebars.render("t", &m);
+
+        assert_eq!(r.ok().unwrap(),
+                   r#"{
+  "test": "something"
+}"#
+                       .to_string());
+    }
+
+    #[test]
+    fn test_handlebars_toml_helper() {
+        let t = Template::compile("{{toml x}}".to_string()).ok().unwrap();
+        let mut data = BTreeMap::new();
+        data.insert("test".into(), "something".into());
+
+        let mut handlebars = Handlebars::new();
+        handlebars.register_helper("toml", Box::new(toml_helper));
+        handlebars.register_template("t", t);
+
+        let mut m: BTreeMap<String, BTreeMap<String, String>> = BTreeMap::new();
+        m.insert("x".into(), data);
+
+        let r = handlebars.render("t", &m);
+
+        assert_eq!(r.ok().unwrap(),
+                   r#"test = "something"
+"#
+                       .to_string());
+    }
+}

components/sup/src/util/mod.rs

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 pub mod convert;
+pub mod handlebars_helpers;
 pub mod path;
 pub mod sys;
 pub mod signals;

www/source/docs/create-packages-configure.html.md

@@ -120,6 +120,68 @@ like this:
     host = host-2
     port = 3434
 
+## File format helpers
+
+### JSON
+
+To output configuration data as JSON, you can use the `json` helper.
+
+Given a default.toml that looks like:
+
+    [web]
+
+    [["servers"]]
+    host = "host-1"
+    port = 4545
+
+    [["servers"]]
+    host = "host-2"
+    port = 3434
+
+and a template:
+
+    {{ json cfg.web }}
+
+when rendered, it will look like:
+
+    {
+      "servers": [
+        {
+          "host": "host-1",
+          "port": 4545
+        },
+        {
+          "host": "host-2",
+          "port": 3434
+        }
+      ]
+    }
+
+This can be useful if you have a confugration file that is in JSON format and
+has the same structure as your TOML configuration data.
+
+### TOML
+
+The `toml` helper can be used to output TOML.
+
+Given a default.toml that looks like:
+
+    [web]
+
+    port = 00
+
+and a template:
+
+    {{ toml cfg.web }}
+
+when rendered, it will look like:
+
+    port = 80
+
+This can be useful if you have an app that uses TOML as its configuration file
+format, but may have not been designed for Habitat, and you only need certain
+parts of the configuration data in the rendered TOML file.
+
 ## Further examples
 
 For an example of how to templatize a configuration file and add it to your plan, see [Add configuration to your plan](/tutorials/getting-started-configure-plan) from the getting started tutorial.