Add multidocument yaml support for output.

Closes issue #54

examples/test_yaml.ucg

@@ -19,11 +19,9 @@ let db_conn2 = mk_db_conn(dbhost2, shared.port, dbname);
 // We have two database connections in a list
 let db_conn_list = [db_conn1, db_conn2];
 
-let connstr_mapper = func (item) => {
-    str = item.conn_string
-};
+let connstr_mapper = func (item) => item.conn_string;
 
-let db_conns = map connstr_mapper.str [db_conn1, db_conn2];
+let db_conns = map(connstr_mapper, [db_conn1, db_conn2]);
 
 let cplx_list = [
     {foo = 1},
@@ -41,4 +39,4 @@ let server_config = {
     l = ["foo", "bar"]
 };
 
-out yaml server_config;
+out yamlmulti [server_config, server_config];

src/convert/mod.rs

@@ -22,6 +22,7 @@ pub mod toml;
 pub mod traits;
 pub mod xml;
 pub mod yaml;
+pub mod yamlmulti;
 
 use std::collections::HashMap;
 
@@ -50,6 +51,7 @@ impl ConverterRegistry {
         registry.register("flags", Box::new(flags::FlagConverter::new()));
         registry.register("exec", Box::new(exec::ExecConverter::new()));
         registry.register("yaml", Box::new(yaml::YamlConverter::new()));
+        registry.register("yamlmulti", Box::new(yamlmulti::MultiYamlConverter::new()));
         registry.register("toml", Box::new(toml::TomlConverter::new()));
         registry.register("xml", Box::new(xml::XmlConverter {}));
         registry

src/convert/yaml.rs

@@ -130,7 +130,7 @@ impl YamlConverter {
         })
     }
 
-    fn write(&self, v: &Val, mut w: &mut dyn Write) -> ConvertResult {
+    pub fn write(&self, v: &Val, mut w: &mut dyn Write) -> ConvertResult {
         let jsn_val = self.convert_value(v)?;
         serde_yaml::to_writer(&mut w, &jsn_val)?;
         writeln!(w, "")?;

src/convert/yaml_help.txt

@@ -7,4 +7,8 @@ They are transformed into toml using the following rules:
 - Int becomes an Int
 - Float becomes a Float
 - Strings become Strings.
-- Functions and Modules are ignored.
+- Functions and Modules are ignored.
+
+If you are using the yamlmulti conversion type then a list will get transformed
+into a yaml document per list item. All other types will get treated as a single
+document.

src/convert/yamlmulti.rs

@@ -0,0 +1,60 @@
+// Copyright 2020 Jeremy Wall
+// 
+// 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 std;
+use std::io::Write;
+use std::rc::Rc;
+
+use crate::convert::yaml::YamlConverter;
+use crate::convert::traits::{ConvertResult, Converter};
+use crate::build::Val;
+
+pub struct MultiYamlConverter (YamlConverter);
+
+impl MultiYamlConverter {
+    pub fn new() -> Self {
+        MultiYamlConverter (YamlConverter::new())
+    }
+
+    pub fn convert_list(&self, vals: &Vec<Rc<Val>>, mut w: &mut dyn Write) -> ConvertResult {
+        for val in vals {
+            self.0.write(val.as_ref(), &mut w)?;
+        }
+        Ok(())
+    }
+}
+
+impl Converter for MultiYamlConverter {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
+        if let Val::List(ref vals) = v.as_ref() {
+            self.convert_list(vals, &mut w)
+        } else {
+            let list = vec![v];
+            self.convert_list(&list, &mut w)
+        }
+    }
+
+    fn file_ext(&self) -> String {
+        "yaml".to_owned()
+    }
+
+    fn description(&self) -> String {
+        "Convert ucg vals into valid multi document yaml.".to_owned()
+    }
+
+    #[allow(unused_must_use)]
+    fn help(&self) -> String {
+        include_str!("yaml_help.txt").to_owned()
+    }
+}