use babel helpers in eval

Author: mmkal

src/presets/eval.ts

@@ -1,4 +1,6 @@
-import {Preset, PresetDependencies} from '.'
+import {Preset} from '.'
+import dedent from 'dedent'
+import {stripTypes} from '../simplify'
 import {definePreset} from './util/standard-schema-preset'
 
 export const _eval = definePreset({'comparison?': '"simplified" | "strict"'}, params => {
@@ -15,17 +17,21 @@ export const _eval = definePreset({'comparison?': '"simplified" | "strict"'}, pa
     if (fnStr.startsWith('/*')) fnStr = fnStr.split('*/').slice(1).join('*/').trim()
     if (before === fnStr) break // the problem isn't comments or whitespace, give up
   }
+  const exampleFn = dedent`
+    const _myFn = () => {
+      return '// abc123'
+    }
+  `
+  const errorSuffix = `\n\nExample:\n\n${exampleFn}`
   if (!fnStr.startsWith('const ')) {
-    throw new Error('Preset function must start with `const ` (e.g. `const _myFn = () => ...`)')
+    throw new Error('Preset function must start with `const `.' + errorSuffix)
   }
   const functionName = fnStr.replace('const ', '').trim().split(/\b/)[0]
   if (!/^[$A-Z_a-z][\w$]*$/.test(functionName)) {
-    throw new Error(
-      'Preset function must have an identifier name (e.g. `const _myFn = () => ...`), got: ' + functionName,
-    )
+    throw new Error('Preset function must start with `const ` and have an identifier name.' + errorSuffix)
   }
 
-  const plainJsFnStr = stripTypes(fnStr, dependencies)
+  const plainJsFnStr = stripTypes(fnStr)
 
   const fnBody = [
     plainJsFnStr, // declare the function
@@ -54,125 +60,3 @@ export const _eval = definePreset({'comparison?': '"simplified" | "strict"'}, pa
 
   return expected
 })
-
-export function stripTypes(typeScriptCode: string, dependencies: PresetDependencies) {
-  const {babelParser, babelTraverse, babelGenerator} = dependencies
-  const ast = babelParser.parse(typeScriptCode, {
-    sourceType: 'unambiguous',
-    plugins: ['typescript'],
-  })
-
-  babelTraverse.default(ast, {
-    // Remove type annotations from function parameters
-    Function(path) {
-      if (path.node.params) {
-        path.node.params.forEach(param => {
-          if ('typeAnnotation' in param) {
-            param.typeAnnotation = null
-          }
-        })
-      }
-      // Remove return type annotation
-      if (path.node.returnType) {
-        path.node.returnType = null
-      }
-    },
-
-    // Remove type annotations from variable declarations
-    VariableDeclarator(path) {
-      if (path.node.id && 'typeAnnotation' in path.node.id) {
-        path.node.id.typeAnnotation = null
-      }
-    },
-
-    // Handle satisfies expressions
-    TSSatisfiesExpression(path) {
-      path.replaceWith(path.node.expression)
-    },
-
-    // Handle type assertions
-    TSAsExpression(path) {
-      path.replaceWith(path.node.expression)
-    },
-
-    TSTypeAssertion(path) {
-      path.replaceWith(path.node.expression)
-    },
-
-    // Remove type-only imports/exports
-    ImportDeclaration(path) {
-      if (path.node.importKind === 'type') {
-        path.remove()
-      }
-    },
-
-    ExportNamedDeclaration(path) {
-      if (path.node.exportKind === 'type') {
-        path.remove()
-      }
-    },
-
-    // Remove type declarations entirely
-    TSTypeAliasDeclaration(path) {
-      path.remove()
-    },
-
-    TSInterfaceDeclaration(path) {
-      path.remove()
-    },
-
-    TSEnumDeclaration(path) {
-      throw new Error(
-        `Can't strip enums. Please don't use them. Found:\n\n${babelGenerator.default(path.node, {comments: true}).code}`,
-      )
-    },
-
-    ClassMethod(path) {
-      if (path.node.kind === 'constructor') {
-        path.node.params.forEach(param => {
-          if ('accessibility' in param || 'readonly' in param) {
-            throw new Error(
-              `Can't strip parameter properties (public/private/protected/readonly). Please don't use them. Found:\n\n${babelGenerator.default(path.node, {comments: true}).code}`,
-            )
-          }
-        })
-      }
-    },
-
-    TSModuleDeclaration(path) {
-      path.remove()
-    },
-
-    // Remove non-null assertions (!)
-    TSNonNullExpression(path) {
-      path.replaceWith(path.node.expression)
-    },
-
-    // Remove type parameters from functions/classes
-    TSTypeParameterDeclaration(path) {
-      path.remove()
-    },
-
-    // Remove type parameters from call expressions
-    CallExpression(path) {
-      if (path.node.typeParameters) {
-        path.node.typeParameters = null
-      }
-    },
-
-    NewExpression(path) {
-      if (path.node.typeParameters) {
-        path.node.typeParameters = null
-      }
-    },
-
-    // Remove definite assignment assertions (!)
-    AssignmentPattern(path) {
-      if (path.node.left && 'definite' in path.node.left && path.node.left.definite) {
-        path.node.left.definite = false
-      }
-    },
-  })
-
-  return babelGenerator.default(ast, {comments: true}).code
-}