Empty moustache gives incomprehensible error

[cshaa]

Package version

6.2.1

Describe the bug

1. Create a simple project as per the docs
2. Into the Edge file, add double curly braces that either contain nothing, or only contain a comment:

Hello {{ /* world */ }}
Hello {{ }}

3. Run the project, and see an nondescriptive and hard to understand error:

node_modules/.pnpm/[email protected]/node_modules/edge-parser/build/index.js:419
  const Expression = expressions_exports[astExpression.type];
                                                       ^

TypeError: Cannot read properties of undefined (reading 'type')
    at transformAst (node_modules/.pnpm/[email protected]/node_modules/edge-parser/build/index.js:419:56)
    at #processMustache (node_modules/.pnpm/[email protected]/node_modules/edge-parser/build/index.js:545:18)
    at Parser.processToken (node_modules/.pnpm/[email protected]/node_modules/edge-parser/build/index.js:592:30)
    at node_modules/.pnpm/[email protected]/node_modules/edge.js/build/index.js:1349:48
    at Array.forEach (<anonymous>)
    at Compiler.compile (node_modules/.pnpm/[email protected]/node_modules/edge.js/build/index.js:1349:22)
    at Template.render (node_modules/.pnpm/[email protected]/node_modules/edge.js/build/chunk-DA7IVQFT.js:578:43)
    at _EdgeRenderer.render (node_modules/.pnpm/[email protected]/node_modules/edge.js/build/index.js:1573:92)
    at _Edge.render (node_modules/.pnpm/[email protected]/node_modules/edge.js/build/index.js:1897:34)
    at Server.<anonymous> (index.js:9:27)

Node.js v23.6.0

I've spent quite some time looking for the type property in our codebase, until I've realized it's in your codebase.

Throwing a more user-friendly error is advisable.

Reproduction repo

https://github.com/cshaa/edge-bug-empty-moustache

[cshaa]

The problem is on this line:

// edge-parser/src/parser/transform_ast.ts

/**
 * Transform acorn AST to Edge AST. This must always be performed before
 * writing it to the compiled template buffer.
 */
export function transformAst(astExpression: any, filename: string, parser: Parser): any {
  const Expression = Expressions[astExpression.type as keyof typeof Expressions]
  if (Expression) {
    return Expression.toStatement(astExpression, filename, parser)
  }

[thetutlage]

I think we can fix this. Feel free to open a PR in the parser codebase for the same 👍