Add a special case to not render anything if the method parameter to the math helper is a template to match the official DustJS implementation.

src/renderer/parameters_context.rs

@@ -24,7 +24,7 @@ use std::collections::HashMap;
 #[derive(Debug)]
 pub struct ParametersContext<'a> {
     parent: Option<&'a ParametersContext<'a>>,
-    params: HashMap<&'a str, Option<BreadcrumbTreeElement<'a>>>,
+    params: HashMap<&'a str, (&'a RValue<'a>, Option<BreadcrumbTreeElement<'a>>)>,
 }
 
 impl<'a> ParametersContext<'a> {
@@ -42,25 +42,26 @@ impl<'a> ParametersContext<'a> {
         // then those are resolved at the time of access rather than
         // the time of assignment, so we leave them into their
         // original IntoContextElement state.
-        let rendered_params: HashMap<&'a str, Option<BreadcrumbTreeElement<'a>>> = params
-            .iter()
-            .map(|kvpair| {
-                let k = kvpair.key;
-                let v: Option<BreadcrumbTreeElement<'a>> = match &kvpair.value {
-                    RValue::RVLiteral(_owned_literal) => {
-                        Some(BreadcrumbTreeElement::from_borrowed(&kvpair.value))
-                    }
-                    RValue::RVPath(_path) => kvpair
-                        .value
-                        .into_context_element(renderer, breadcrumbs)
-                        .map(std::convert::From::from),
-                    RValue::RVTemplate(_template) => {
-                        Some(BreadcrumbTreeElement::from_borrowed(&kvpair.value))
-                    }
-                };
-                (k, v)
-            })
-            .collect();
+        let rendered_params: HashMap<&'a str, (&'a RValue<'a>, Option<BreadcrumbTreeElement<'a>>)> =
+            params
+                .iter()
+                .map(|kvpair| {
+                    let k = kvpair.key;
+                    let v: Option<BreadcrumbTreeElement<'a>> = match &kvpair.value {
+                        RValue::RVLiteral(_owned_literal) => {
+                            Some(BreadcrumbTreeElement::from_borrowed(&kvpair.value))
+                        }
+                        RValue::RVPath(_path) => kvpair
+                            .value
+                            .into_context_element(renderer, breadcrumbs)
+                            .map(std::convert::From::from),
+                        RValue::RVTemplate(_template) => {
+                            Some(BreadcrumbTreeElement::from_borrowed(&kvpair.value))
+                        }
+                    };
+                    (k, (&kvpair.value, v))
+                })
+                .collect();
 
         ParametersContext {
             parent: parent,
@@ -70,7 +71,7 @@ impl<'a> ParametersContext<'a> {
 
     pub fn from_values(
         parent: Option<&'a ParametersContext<'a>>,
-        params: HashMap<&'a str, Option<BreadcrumbTreeElement<'a>>>,
+        params: HashMap<&'a str, (&'a RValue<'a>, Option<BreadcrumbTreeElement<'a>>)>,
     ) -> Self {
         ParametersContext {
             parent: parent,
@@ -85,6 +86,17 @@ impl<'a> ParametersContext<'a> {
                 .map(|p| p.contains_key(segment))
                 .unwrap_or(false)
     }
+
+    pub fn get_original_rvalue(&self, segment: &str) -> Option<&'a RValue<'a>> {
+        self.params
+            .get(segment)
+            .map(|(rvalue, _bte)| *rvalue)
+            .or_else(|| {
+                self.parent
+                    .map(|p| p.get_original_rvalue(segment))
+                    .flatten()
+            })
+    }
 }
 
 impl<'a> IntoContextElement for ParametersContext<'a> {
@@ -99,7 +111,7 @@ impl<'a> IntoContextElement for ParametersContext<'a> {
 
 impl<'a> Walkable for ParametersContext<'a> {
     fn walk(&self, segment: &str) -> Result<&dyn IntoContextElement, WalkError> {
-        match self.params.get(segment) {
+        match self.params.get(segment).map(|(_rvalue, bte)| bte) {
             Some(Some(bte)) => Ok(bte.borrow()),
             Some(None) => Err(WalkError::CantWalk),
             None => self

src/renderer/renderer.rs

@@ -5,6 +5,7 @@ use crate::parser::Filter;
 use crate::parser::OwnedLiteral;
 use crate::parser::PartialNameElement;
 use crate::parser::Path;
+use crate::parser::RValue;
 use crate::parser::Special;
 use crate::parser::Template;
 use crate::parser::TemplateElement;
@@ -675,8 +676,13 @@ impl<'a> DustRenderer<'a> {
 
                         // Generate a ParametersContext with the result of the math operation as key
                         let converted_value: BreadcrumbTreeElement<'_> = calculated_value.into();
-                        let calculated_param_map: HashMap<&str, Option<BreadcrumbTreeElement<'_>>> =
-                            vec![("key", Some(converted_value))].into_iter().collect();
+                        let dummy_rvalue = RValue::RVLiteral(OwnedLiteral::LPositiveInteger(0));
+                        let calculated_param_map: HashMap<
+                            &str,
+                            (&RValue<'_>, Option<BreadcrumbTreeElement<'_>>),
+                        > = vec![("key", (&dummy_rvalue, Some(converted_value)))]
+                            .into_iter()
+                            .collect();
                         let calculated_context =
                             ParametersContext::from_values(None, calculated_param_map);
                         // calculate are_any_checks_true
@@ -982,6 +988,21 @@ impl<'a> DustRenderer<'a> {
         breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
         math_parameters: &'a ParametersContext<'a>,
     ) -> Option<IceResult<'a>> {
+        // Special case: if method is a template then do not render
+        // anything. This is to match the behavior of dustjs even
+        // though it works fine.
+        match math_parameters.get_original_rvalue("method") {
+            Some(RValue::RVTemplate(template)) => {
+                if template.iter().any(|pne| match pne {
+                    PartialNameElement::PNReference { .. } => true,
+                    PartialNameElement::PNSpan { .. } => false,
+                }) {
+                    return None;
+                }
+            }
+            _ => (),
+        }
+
         let method = match self.tap(breadcrumbs, math_parameters, "method") {
             None | Some(Err(_)) => return None,
             Some(Ok(ice_result)) => ice_result,