chore: Add an example using all backends a modern application may want

Author: Geod24

.gitignore

@@ -30,3 +30,4 @@ docs/
 
 # Examples binary
 examples/helloworld/helloworld
+examples/full/myapp

examples/full/dub.json

@@ -0,0 +1,6 @@
+{
+    "name": "myapp",
+    "dependencies": {
+        "configy": { "path": "../../", "version": "*" }
+    }
+}

examples/full/dub.selections.json

@@ -0,0 +1,8 @@
+{
+	"fileVersion": 1,
+	"versions": {
+		"configy": {"path":"../../"},
+		"dyaml": "0.10.0",
+		"tinyendian": "0.2.0"
+	}
+}

examples/full/myconfig.yaml

@@ -0,0 +1,3 @@
+attendee:
+    - name: John Doe
+    - name: Jany Dirkin

examples/full/source/app.d

@@ -0,0 +1,67 @@
+module helloworld;
+
+import configy.easy;
+
+import std.stdio;
+import std.typecons;
+
+struct FriendConfig
+{
+    string name;
+    @Optional int age;
+}
+
+struct Config
+{
+    string user;
+    SetInfo!int frequency;
+    FriendConfig witness;
+    FriendConfig[] attendee;
+}
+
+int main (string[] clargs)
+{
+    // This will read `args` (and modify it a la `getopt`), look up `config.yaml`,
+    // and the environment using the binary name as prefix.
+    CLIArgs args;
+    args.parse(clargs);
+    Nullable!Config configN = parseAppConfiguration!Config(args);
+    if (configN.isNull())
+        return 1;
+    auto config = configN.get();
+
+    writeln("Configuration: ", config);
+
+    // From environment (`MYAPP_USER`)
+    assert(config.user == "John Smith");
+    // From the command line
+    assert(config.frequency == 42);
+    assert(config.frequency.set == true);
+
+    // Name comes from arg, age from env
+    assert(config.witness == FriendConfig("Kevin Bacon", 121));
+
+    // From the configuration file
+    assert(config.attendee.length == 2);
+    assert(config.attendee[0] == FriendConfig("John Doe"));
+    assert(config.attendee[1] == FriendConfig("Jany Dirkin", 27));
+
+    assert(clargs == [ "./myapp", "some", "positional", "arguments" ]);
+
+    return 0;
+}
+
+private ConfigT parseAppConfiguration (ConfigT) (in CLIArgs args)
+{
+    import configy.backend.arguments;
+    import configy.backend.environment;
+    import configy.backend.multi;
+    import configy.backend.node;
+    import configy.backend.yaml;
+
+    Mapping args_root = ArgumentBackend.make(args.overrides);
+    Mapping env_root = EnvironmentBackend.make(`MYAPP`);
+    Mapping yaml_root = parseFile(args.config_path);
+    scope root = MultiBackend.make([args_root, env_root, yaml_root]);
+    return parseConfig!ConfigT(root);
+}

examples/full/test.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/bash
+
+export MYAPP_USER="John Smith"
+# Will be overriden by CLI
+export MYAPP_FREQUENCY=32
+# Will be overriden by CLI
+export MYAPP_WITNESS_NAME="Solomon"
+export MYAPP_WITNESS_AGE=121
+
+exec dub run -- some -O witness.name="Kevin Bacon" positional -O frequency=42 arguments -c myconfig.yaml