feat(error): Improve missing variable errors

cobalt-org · Nov 19, 2018 · d6e1aea · d6e1aea
1 parent 45c5d39
commit d6e1aea
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Showing 3 changed files with 51 additions and 4 deletions.
diff --git a/liquid-interpreter/src/globals.rs b/liquid-interpreter/src/globals.rs
@@ -54,10 +54,28 @@ impl Globals for Object {
     }
 
     fn get_variable<'a>(&'a self, path: PathRef) -> Result<&'a Value> {
-        self.try_get_variable(path).ok_or_else(|| {
-            let path = itertools::join(path.iter(), ".");
-            Error::with_msg("Unknown index").context("variable", format!("{}", path))
-        })
+        if let Some(res) = self.try_get_variable(path) {
+            return Ok(res);
+        } else {
+            for cur_idx in 1..path.len() {
+                let subpath_end = path.len() - cur_idx;
+                let subpath = &path[0..subpath_end];
+                if let Some(parent) = self.try_get_variable(subpath) {
+                    let subpath = itertools::join(subpath.iter(), ".");
+                    let index = &path[subpath_end];
+                    let available = itertools::join(parent.keys(), ", ");
+                    return Err(Error::with_msg("Unknown index")
+                        .context("variable", format!("{}", subpath))
+                        .context("requested index", format!("{}", index))
+                        .context("available indexes", format!("{}", available)));
+                }
+            }
+
+            let available = itertools::join(self.keys(), ", ");
+            return Err(Error::with_msg("Unknown variable")
+                .context("requested variable", path[0].to_str().into_owned())
+                .context("available variables", available));
+        }
     }
 }
 

diff --git a/liquid-value/src/scalar.rs b/liquid-value/src/scalar.rs
@@ -174,6 +174,14 @@ impl From<&'static str> for Scalar {
     }
 }
 
+impl From<borrow::Cow<'static, str>> for Scalar {
+    fn from(s: borrow::Cow<'static, str>) -> Self {
+        Scalar {
+            0: ScalarEnum::Str(s),
+        }
+    }
+}
+
 impl PartialEq<Scalar> for Scalar {
     fn eq(&self, other: &Self) -> bool {
         match (&self.0, &other.0) {

diff --git a/liquid-value/src/values.rs b/liquid-value/src/values.rs
@@ -213,6 +213,27 @@ impl Value {
         }
     }
 
+    /// All keys
+    pub fn keys(&self) -> Vec<Scalar> {
+        match *self {
+            Value::Array(ref x) => {
+                let start: i32 = 0;
+                let end = x.len() as i32;
+                let mut keys: Vec<_> = (start..end).map(|i| Scalar::new(i)).collect();
+                keys.push(Scalar::new("first"));
+                keys.push(Scalar::new("last"));
+                keys
+            }
+            Value::Object(ref x) => x.keys().map(|s| {
+                match *s {
+                    borrow::Cow::Borrowed(s) => Scalar::new(s),
+                    borrow::Cow::Owned(ref s) => Scalar::new(s.to_owned()),
+                }
+            }).collect(),
+            _ => vec![],
+        }
+    }
+
     /// Access a contained `Value`.
     pub fn get<'s>(&'s self, index: &Scalar) -> Option<&'s Self> {
         match *self {