Turns out the issue was the trailing space on the parameters.

src/parser/parser.rs

@@ -6,7 +6,7 @@ use nom::bytes::complete::{tag, take_until, take_until_parser_matches};
 use nom::character::complete::line_ending;
 use nom::character::complete::multispace0;
 use nom::character::complete::one_of;
-use nom::character::complete::space1;
+use nom::character::complete::{space0, space1};
 use nom::combinator::all_consuming;
 use nom::combinator::map;
 use nom::combinator::opt;
@@ -387,7 +387,11 @@ where
         let (i, (name, params, inner, maybe_else, _closing_name)) = tuple((
             preceded(tag(open_matcher), tag(tag_name)),
             terminated(
-                opt(preceded(space1, separated_list1(space1, key_value_pair))),
+                opt(delimited(
+                    space1,
+                    separated_list1(space1, key_value_pair),
+                    space0,
+                )),
                 tag("}"),
             ),
             opt(body),
@@ -420,7 +424,11 @@ where
             tag(open_matcher),
             tuple((
                 tag(tag_name),
-                opt(preceded(space1, separated_list1(space1, key_value_pair))),
+                opt(delimited(
+                    space1,
+                    separated_list1(space1, key_value_pair),
+                    space0,
+                )),
             )),
             tag("/}"),
         )(i)?;
@@ -449,7 +457,11 @@ where
             tag(open_matcher),
             tuple((
                 alt((map(key, String::from), quoted_string)),
-                opt(preceded(space1, separated_list1(space1, key_value_pair))),
+                opt(delimited(
+                    space1,
+                    separated_list1(space1, key_value_pair),
+                    space0,
+                )),
             )),
             tag("/}"),
         )(i)?;
@@ -1056,7 +1068,9 @@ mod tests {
     #[test]
     fn test_full_document_parameterized_partial() {
         assert_eq!(
-            super::template(r#"{#level3.level4}{>partialtwo v1="b"/}{/level3.level4}"#),
+            super::template(
+                r#"{#level3.level4}{>partialtwo v1="b" v2="b" v3="b" v4="b" v5="b" /}{/level3.level4}"#
+            ),
             Ok::<_, nom::Err<(&str, ErrorKind)>>((
                 "",
                 Template {
@@ -1069,10 +1083,28 @@ mod tests {
                                 elements: vec![TemplateElement::TETag(DustTag::DTPartial(
                                     Partial {
                                         name: "partialtwo".to_owned(),
-                                        params: vec![KVPair {
+                                        params: vec![
+                                            KVPair {
                                                 key: "v1",
                                                 value: RValue::RVString("b".to_owned())
-                                        }]
+                                            },
+                                            KVPair {
+                                                key: "v2",
+                                                value: RValue::RVString("b".to_owned())
+                                            },
+                                            KVPair {
+                                                key: "v3",
+                                                value: RValue::RVString("b".to_owned())
+                                            },
+                                            KVPair {
+                                                key: "v4",
+                                                value: RValue::RVString("b".to_owned())
+                                            },
+                                            KVPair {
+                                                key: "v5",
+                                                value: RValue::RVString("b".to_owned())
+                                            }
+                                        ]
                                     }
                                 ))]
                             }),

src/renderer/walking.rs

@@ -0,0 +1,53 @@
+use crate::renderer::context_element::ContextElement;
+use crate::renderer::WalkError;
+
+enum WalkResult<'a> {
+    NoWalk,
+    PartialWalk,
+    FullyWalked(&'a dyn ContextElement),
+}
+
+fn walk_path_from_single_level<'a>(
+    context: &'a dyn ContextElement,
+    path: &Vec<&str>,
+) -> WalkResult<'a> {
+    if path.is_empty() {
+        return WalkResult::FullyWalked(context);
+    }
+
+    let mut walk_failure = WalkResult::NoWalk;
+    let mut output = context;
+    for elem in path.iter() {
+        let new_val = output.walk(elem);
+        match output.walk(elem) {
+            Err(WalkError::CantWalk { .. }) => {
+                return walk_failure;
+            }
+            Ok(new_val) => {
+                walk_failure = WalkResult::PartialWalk;
+                output = new_val;
+            }
+        }
+    }
+
+    WalkResult::FullyWalked(output)
+}
+
+pub fn walk_path<'a>(
+    breadcrumbs: &Vec<&'a dyn ContextElement>,
+    path: &'a Vec<&str>,
+) -> Result<&'a dyn ContextElement, WalkError> {
+    for context in breadcrumbs.iter().rev() {
+        match walk_path_from_single_level(*context, path) {
+            // If no walking was done at all, keep looping
+            WalkResult::NoWalk => {}
+            // If we partially walked then stop trying to find
+            // anything
+            WalkResult::PartialWalk => {
+                return Err(WalkError::CantWalk);
+            }
+            WalkResult::FullyWalked(new_context) => return Ok(new_context),
+        }
+    }
+    Err(WalkError::CantWalk)
+}