docs(YAML): adds examples for using YAML to build a CLI

Author: kbknapp

examples/17_yaml.rs

@@ -0,0 +1,45 @@
+// In order to use YAML to define your CLI you must compile clap with the "yaml" feature becasue
+// it's **not** included by default.
+//
+// In order to do this, ensure your Cargo.toml looks like one of the following:
+//
+// [dependencies.clap]
+// features = ["yaml"]
+//
+// __OR__
+//
+// [dependencies]
+// clap = { features = ["yaml"] }
+
+
+// Using yaml requires calling a clap macro `load_yaml!()` so we must use the '#[macro_use]'
+// directive
+#[macro_use]
+extern crate clap;
+
+use clap::App;
+
+fn main() {
+    // To load a yaml file containing our CLI definition such as the example '17_yaml.yml' we can
+    // use the convenience macro which loads the file at compile relative to the current file
+    // similiar to how modules are found.
+    //
+    // Then we pass that yaml object to App to build the CLI.
+    //
+    // Finally we call get_matches() to start the parsing process. We use the matches just as we
+    // normally would
+    let yml = load_yaml!("17_yaml.yml");
+    let m = App::from_yaml(yml).get_matches();
+
+    // Because the example 17_yaml.yml is rather large we'll just look a single arg so you can
+    // see that it works...
+    if let Some(mode) = m.value_of("mode") {
+        match mode {
+            "fast" => println!("We're really going now!"),
+            "slow" => println!("Awwww, too slow :(")
+            _      => unreachable!()
+        }
+    } else {
+        println!("--mode <MODE> wasn't used...");
+    }
+}

examples/17_yaml.yml

@@ -0,0 +1,96 @@
+name: yml_app
+version: 1.0
+about: an example using a .yml file to build a CLI
+author: Kevin K. <[email protected]>
+
+# AppSettings can be defined as a list and are **not** ascii case sensitive
+settings: 
+    - ArgRequiredElseHelp
+
+# All Args must be defined in the 'args:' list where the name of the arg, is the
+# key to a Hash object
+args:
+    # The name of this argument, is 'opt' which will be used to access the value
+    # later in your Rust code
+    - opt:
+        help: example option argument from yaml
+        short: o
+        long: option
+        multiple: true
+        takes_value: true
+    - pos:
+        help: example positional argument from yaml
+        index: 1
+        # A list of possible values can be defined as a list
+        possible_values:
+            - fast
+            - slow
+    - flag:
+        help: demo flag argument
+        short: F
+        multiple: true
+        global: true
+        # Conflicts, mutual overrides, and requirements can all be defined as a
+        # list, where the key is the name of the other argument
+        conflicts_with:
+            - opt
+        requires:
+            - pos
+    - mode:
+        long: mode
+        help: shows an option with specific values
+        # possible_values can also be defined in this list format
+        possible_values: [ vi, emacs ]
+    - mvals:
+        long: mult-vals
+        help: demos an option which has two named values
+        # value names can be described in a list, where the help will be shown
+        # --mult-vals <one> <two>
+        value_names:
+            - one
+            - two
+    - minvals:
+        long: min-vals
+        multiple: true
+        help: you must supply at least two values to satisfy me
+        min_values: 2
+    - maxvals:
+        long: max-vals
+        multiple: true
+        help: you can only supply a max of 3 values for me!
+        max_values: 3
+
+# All subcommands must be listed in the 'subcommand:' object, where the key to
+# the list is the name of the subcommand, and all settings for that command are
+# are part of a Hash object
+subcommands:
+    # The nae of this subcommand will be 'subcmd' which can be accessed in your
+    # Rust code later
+    - subcmd:
+        about: demos subcommands from yaml
+        version: 0.1
+        author: Kevin K. <[email protected]>
+        # Subcommand args are exactly like App args
+        args:
+            - scopt:
+                short: B
+                multiple: true
+                help: example subcommand option
+                takes_value: true
+            - scpos1:
+                help: example subcommand positional
+                index: 1
+
+# ArgGroups are supported as well, and must be sepcified in the 'arg_groups:'
+# object of this file
+arg_groups:
+    # the name of the ArgGoup is specified here
+    - min-max-vals:
+        # All args and groups that are a part of this group are set here
+        args:
+            - minvals
+            - maxvals
+        # setting conflicts is done the same manner as setting 'args:'
+        #
+        # to make this group required, you could set 'required: true' but for
+        # this example we won't do that.

src/app/app.rs

@@ -148,7 +148,16 @@ impl<'a, 'v, 'ab, 'u, 'h, 'ar> App<'a, 'v, 'ab, 'u, 'h, 'ar>{
         }
     }
 
-    /// Creates a new instace of `App` from a .yml (YAML) file.
+    /// Creates a new instace of `App` from a .yml (YAML) file. The YAML file must be properly
+    /// formatted or this function will panic!(). A full example of supported YAML objects can be
+    /// found in `examples/17_yaml.rs` and `examples/17_yaml.yml`.
+    ///
+    /// In order to use this function you must compile with the `features = ["yaml"]` in your
+    /// settings for `[dependencies.clap]` table of your `Cargo.toml`
+    ///
+    /// Note, due to how the YAML objects are built there is a convienience macro for loading the
+    /// YAML file (relative to the current file, like modules work). That YAML object can then be
+    /// passed to this function.
     ///
     /// # Example
     ///

tests/app.yml

@@ -2,7 +2,8 @@ name: claptests
 version: 1.0
 about: tests clap library
 author: Kevin K. <[email protected]>
-settings: ArgRequiredElseHelp
+settings: 
+    - ArgRequiredElseHelp
 args:
     - opt:
         short: o