Improve UndefinedVariableError and UndefinedFilterError error messages (#180)

Author: Cervajz

CHANGELOG.md

@@ -1,3 +1,14 @@
+# [Unreleased]
+
+## Enhancements
+
+* Align the `Solid.UndefinedFilterError` message with `Solid.UndefinedVariableError` - include line number
+
+## Bug fixes
+
+* Return `{:error, errors}` tuple when both strict_filters and strict_variables are enforced while rendering a template
+* Use correct variable name in the `Solid.UndefinedVariableError` message
+
 # 1.0.1 (2025-07-04)
 
 ## Bug fixes

lib/solid/argument.ex

@@ -187,7 +187,11 @@ defmodule Solid.Argument do
       {:error, {:not_found, key}, context} ->
         context =
           if strict_variables do
-            Context.put_errors(context, %UndefinedVariableError{variable: key, loc: arg.loc})
+            Context.put_errors(context, %UndefinedVariableError{
+              variable: key,
+              original_name: arg.original_name,
+              loc: arg.loc
+            })
           else
             context
           end

lib/solid/undefined_filter_error.ex

@@ -3,5 +3,9 @@ defmodule Solid.UndefinedFilterError do
   defexception [:filter, :loc]
 
   @impl true
-  def message(exception), do: "Undefined filter #{exception.filter}"
+  def message(exception) do
+    line = exception.loc.line
+    reason = "Undefined filter #{exception.filter}"
+    "#{line}: #{reason}"
+  end
 end

lib/solid/undefined_variable_error.ex

@@ -1,11 +1,11 @@
 defmodule Solid.UndefinedVariableError do
   @type t :: %__MODULE__{}
-  defexception [:variable, :loc]
+  defexception [:variable, :original_name, :loc]
 
   @impl true
   def message(exception) do
     line = exception.loc.line
-    reason = "Undefined variable #{exception.variable}"
+    reason = "Undefined variable #{exception.original_name}"
     "#{line}: #{reason}"
   end
 end

test/solid/argument_test.exs

@@ -296,7 +296,10 @@ defmodule Solid.ArgumentTest do
       arg = %Variable{original_name: "key[1]", loc: @loc, identifier: "key", accesses: accesses}
       context = %Solid.Context{vars: %{"key" => "a string"}}
       assert {:ok, nil, context} = Argument.get(arg, context, [], strict_variables: true)
-      assert context.errors == [%UndefinedVariableError{variable: ["key", 1], loc: @loc}]
+
+      assert context.errors == [
+               %UndefinedVariableError{variable: ["key", 1], original_name: "key[1]", loc: @loc}
+             ]
     end
 
     test "array access and nested" do
@@ -376,7 +379,9 @@ defmodule Solid.ArgumentTest do
       assert {:ok, 456, context} =
                Argument.get(arg, context, filters, strict_variables: true)
 
-      assert context.errors == [%UndefinedVariableError{variable: ["key"], loc: @loc}]
+      assert context.errors == [
+               %UndefinedVariableError{variable: ["key"], original_name: "key", loc: @loc}
+             ]
     end
 
     test "missing filter strict_filters" do
@@ -445,7 +450,7 @@ defmodule Solid.ArgumentTest do
 
       assert context.errors == [
                %Solid.UndefinedFilterError{filter: "unknown", loc: @loc},
-               %UndefinedVariableError{variable: ["key"], loc: @loc}
+               %UndefinedVariableError{variable: ["key"], original_name: "key", loc: @loc}
              ]
     end
 
@@ -523,7 +528,9 @@ defmodule Solid.ArgumentTest do
                  strict_variables: true
                )
 
-      assert context.errors == [%UndefinedVariableError{variable: ["name"], loc: @loc}]
+      assert context.errors == [
+               %UndefinedVariableError{variable: ["name"], original_name: "name", loc: @loc}
+             ]
     end
   end
 end

test/solid_test.exs

@@ -213,10 +213,12 @@ defmodule SolidTest do
       assert error == [
                %Solid.UndefinedVariableError{
                  variable: ["var1"],
+                 original_name: "var1",
                  loc: %Solid.Parser.Loc{line: 1, column: 5}
                },
                %Solid.UndefinedVariableError{
                  variable: ["var2"],
+                 original_name: "var2",
                  loc: %Solid.Parser.Loc{line: 1, column: 16}
                }
              ]
@@ -254,16 +256,19 @@ defmodule SolidTest do
       assert error == [
                %Solid.UndefinedVariableError{
                  variable: ["var1"],
+                 original_name: "var1",
                  loc: %Solid.Parser.Loc{line: 1, column: 5}
                },
                %Solid.UndefinedVariableError{
                  variable: ["var2"],
+                 original_name: "var2",
                  loc: %Solid.Parser.Loc{line: 1, column: 16}
                },
                # FIXME this should somehow point out which file?
                # Check how liquid does this
                %Solid.UndefinedVariableError{
                  variable: ["var3"],
+                 original_name: "var3",
                  loc: %Solid.Parser.Loc{line: 1, column: 4}
                }
              ]
@@ -296,6 +301,7 @@ defmodule SolidTest do
       assert error == [
                %Solid.UndefinedVariableError{
                  variable: ["var1"],
+                 original_name: "var1",
                  loc: %Solid.Parser.Loc{line: 1, column: 5}
                },
                %Solid.UndefinedFilterError{
@@ -304,9 +310,47 @@ defmodule SolidTest do
                },
                %Solid.UndefinedVariableError{
                  variable: ["var2"],
+                 original_name: "var2",
                  loc: %Solid.Parser.Loc{line: 1, column: 38}
                }
              ]
     end
+
+    test "undefined variable error message with multiple variables" do
+      template =
+        "{{ var1 }}\n{{ event.name }}\n{{ user.properties['name'] }}\n"
+
+      {:error, [first_error, second_error, third_error], _partial_result} =
+        template
+        |> Solid.parse!()
+        |> Solid.render(%{}, strict_variables: true, file_system: {TestFileSystem, nil})
+
+      assert String.contains?(Solid.UndefinedVariableError.message(first_error), "var1")
+
+      assert String.contains?(
+               Solid.UndefinedVariableError.message(second_error),
+               "event.name"
+             )
+
+      assert String.contains?(
+               Solid.UndefinedVariableError.message(third_error),
+               "user.properties['name']"
+             )
+    end
+
+    test "undefined filter error message with line number" do
+      template = "{{ var1 | not_a_filter }}"
+
+      assert_raise Solid.RenderError,
+                   "1 error(s) found while rendering\n1: Undefined filter not_a_filter",
+                   fn ->
+                     template
+                     |> Solid.parse!()
+                     |> Solid.render!(%{"var1" => "value"},
+                       strict_filters: true,
+                       file_system: {TestFileSystem, nil}
+                     )
+                   end
+    end
   end
 end