Add list_variables method

Cargo.lock

@@ -46,7 +46,7 @@ dependencies = [
 
 [[package]]
 name = "blueprint"
-version = "0.3.0"
+version = "0.4.0"
 dependencies = [
  "nom",
  "structopt",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "blueprint"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["Joakim Hulthe <joakim@hulthe.net>"]
 description = "A simple templating library"
 edition = "2018"

src/ast.rs

@@ -53,10 +53,23 @@ impl Template<'_> {
         }
         Ok(())
     }
+
+    pub fn list_variables(&self) -> Vec<&str> {
+        let mut vars: Vec<_> = self
+            .parts
+            .iter()
+            .flat_map(|part| part.list_variables())
+            .collect();
+
+        vars.sort_unstable();
+        vars.dedup();
+
+        vars
+    }
 }
 
 impl Part<'_> {
-    pub fn write(&self, env: &Env, w: &mut impl Write) -> io::Result<()> {
+    fn write(&self, env: &Env, w: &mut impl Write) -> io::Result<()> {
         match self {
             Part::Text(text) => w.write_all(text.as_bytes())?,
             Part::If {
@@ -81,10 +94,34 @@ impl Part<'_> {
         }
         Ok(())
     }
+
+    fn list_variables(&self) -> Vec<&str> {
+        match self {
+            Part::Text(_) => vec![],
+            Part::If {
+                if_then,
+                elifs,
+                else_part,
+            } => {
+                let if_then = if_then.list_variables().into_iter();
+
+                let elifs = elifs.iter().flat_map(|elif| elif.list_variables());
+
+                if let Some(else_part) = else_part {
+                    if_then
+                        .chain(elifs)
+                        .chain(else_part.list_variables())
+                        .collect()
+                } else {
+                    if_then.chain(elifs).collect()
+                }
+            }
+        }
+    }
 }
 
 impl IfThen<'_> {
-    pub fn write(&self, env: &Env, w: &mut impl Write) -> io::Result<bool> {
+    fn write(&self, env: &Env, w: &mut impl Write) -> io::Result<bool> {
         let cond = self.cond.eval(env);
         let cond = match &*cond {
             &Value::Bool(cond) => cond,
@@ -100,10 +137,18 @@ impl IfThen<'_> {
 
         Ok(cond)
     }
+
+    fn list_variables(&self) -> Vec<&str> {
+        self.parts
+            .iter()
+            .flat_map(|part| part.list_variables())
+            .chain(self.cond.list_variables().into_iter())
+            .collect()
+    }
 }
 
 impl Expr<'_> {
-    pub fn eval<'a>(&self, env: &'a Env) -> Cow<'a, Value> {
+    fn eval<'a>(&self, env: &'a Env) -> Cow<'a, Value> {
         match self {
             Expr::Variable(var) => Cow::Borrowed(env.get(&**var).unwrap_or(&Value::Null)),
             Expr::Str(s) => Cow::Owned(Value::Str(s.to_string())),
@@ -136,4 +181,16 @@ impl Expr<'_> {
             }
         }
     }
+
+    fn list_variables(&self) -> Vec<&str> {
+        match self {
+            Expr::Variable(var) => vec![var],
+            Expr::Str(_) => vec![],
+            Expr::Cmp { expr1, expr2, .. } => expr1
+                .list_variables()
+                .into_iter()
+                .chain(expr2.list_variables())
+                .collect(),
+        }
+    }
 }

src/lib.rs

@@ -173,4 +173,15 @@ mod test {
 
         assert_eq!(ast, expected);
     }
+
+    #[test]
+    fn test_list_vars() {
+        let input = "one {% if foo %} two {% if bar %} three {% end %} four {% end %} five";
+        let ast = parse_template(&input).expect("failed to parse");
+
+        let expected = vec!["bar", "foo"];
+        let actual = ast.list_variables();
+
+        assert_eq!(actual, expected);
+    }
 }

src/main.rs

@@ -5,17 +5,19 @@ use std::path::PathBuf;
 use structopt::StructOpt;
 
 #[derive(StructOpt)]
-struct Opt {
-    template: PathBuf,
-    env: Vec<String>,
+enum Opt {
+    Eval { template: PathBuf, env: Vec<String> },
+    ListVars { template: PathBuf },
 }
 
 fn main() {
     let opt = Opt::from_args();
-    let file = read_to_string(&opt.template).expect("failed to load file");
+
+    match opt {
+        Opt::Eval { template, env } => {
+            let file = read_to_string(template).expect("failed to load file");
             let template = blueprint::parse_template(&file).expect("failed to parse");
-    let env = opt
-        .env
+            let env = env
                 .into_iter()
                 .map(|key| (key, Value::Bool(true)))
                 .collect();
@@ -25,3 +27,14 @@ fn main() {
                 .write(&env, &mut stdout)
                 .expect("failed to write output");
         }
+
+        Opt::ListVars { template } => {
+            let file = read_to_string(template).expect("failed to load file");
+            let template = blueprint::parse_template(&file).expect("failed to parse");
+
+            for var in template.list_variables() {
+                println!("{}", var);
+            }
+        }
+    }
+}

src/parser.rs

@@ -86,7 +86,7 @@ fn text_part(i: &str) -> IResult<&str, Part> {
     //eprintln!("text_part 2    \"{}\"", i);
     let (i, o) = r.unwrap_or(("", i));
     //eprintln!("text_part 3    \"{}\"", i);
-    if o == "" {
+    if o.is_empty() {
         //eprintln!("text_part 4A    \"{}\"", i);
         Err(nom::Err::Error(nom::error::Error::new(
             i,
@@ -168,11 +168,11 @@ pub fn parse_template(template: &str) -> Result<Template, Error> {
         Ok((rest, parts)) => {
             //eprintln!("{:#?}", parts);
 
-            if rest != "" {
+            if rest.is_empty() {
+                Ok(Template { parts })
+            } else {
                 //panic!("failed to parse input. remainder: \"{}\"", rest);
                 Err(Error::ParseError)
-            } else {
-                Ok(Template { parts })
             }
         }
         Err(_e) => {