fix(twoslash): improve cuts parser & error messages (#77)

Author: fuma-nama

packages/twoslash/src/regexp.ts

@@ -2,8 +2,8 @@ export const reConfigBoolean = /^\/\/\s?@(\w+)$/gm
 export const reConfigValue = /^\/\/\s?@(\w+):\s?(.+)$/gm
 export const reAnnonateMarkers = /^\s*\/\/\s*\^(\?|\||\^+)( .*)?$/gm
 
-export const reCutBefore = /^[\t\v\f ]*\/\/\s?---cut(-before)?---\r?\n/gm
-export const reCutAfter = /^[\t\v\f ]*\/\/\s?---cut-after---$/gm
-export const reCutStart = /^[\t\v\f ]*\/\/\s?---cut-start---$/gm
-export const reCutEnd = /^[\t\v\f ]*\/\/\s?---cut-end---\r?\n/gm
+export const reCutBefore = /^\/\/\s?---cut(-before)?---$/
+export const reCutAfter = /^\/\/\s?---cut-after---$/
+export const reCutStart = /^\/\/\s?---cut-start---$/
+export const reCutEnd = /^\/\/\s?---cut-end---$/
 export const reFilenamesMakers = /^[\t\v\f ]*\/\/\s?@filename: (.+)$/gm

packages/twoslash/src/utils.ts

@@ -260,40 +260,61 @@ export function findFlagNotations(code: string, customTags: string[], tsOptionDe
 }
 
 export function findCutNotations(code: string, meta: Pick<TwoslashReturnMeta, 'removals'>) {
-  const removals: Range[] = []
+  let removals: Range[] = []
+  const lines = code.split('\n')
+  const cutStarts: number[] = []
+  // start character after \n
+  let idx = 0
+  let lineIndex = 0
+
+  for (const line of lines) {
+    const comment = line.trim()
+
+    if (comment.match(reCutBefore)) {
+      removals = [[0, idx + line.length + 1]]
+    }
+    else if (comment.match(reCutAfter)) {
+      removals.push([idx, code.length])
+      break
+    }
+    else if (comment.match(reCutStart)) {
+      cutStarts.push(idx)
+    }
+    else if (comment.match(reCutEnd)) {
+      const startIdx = cutStarts.pop()
+
+      if (startIdx === undefined) {
+        const startLine = lines.findIndex((line, i) => i > lineIndex && line.trim().match(reCutStart))
+
+        if (startLine === -1) {
+          throw new TwoslashError(
+            `Mismatched cut markers`,
+            `You have an unclosed the cut-end at line ${lineIndex + 1}`,
+            `Make sure you have a matching pair for each.`,
+          )
+        }
 
-  const cutBefore = [...code.matchAll(reCutBefore)]
-  const cutAfter = [...code.matchAll(reCutAfter)]
-  const cutStart = [...code.matchAll(reCutStart)]
-  const cutEnd = [...code.matchAll(reCutEnd)]
+        throw new TwoslashError(
+          `Mismatched cut markers`,
+          `You have a cut-start at line ${startLine + 1} which is after the cut-end at line ${lineIndex + 1}`,
+          `Make sure you have a matching pair for each.`,
+        )
+      }
 
-  if (cutBefore.length) {
-    const last = cutBefore[cutBefore.length - 1]
-    removals.push([0, last.index! + last[0].length])
-  }
-  if (cutAfter.length) {
-    const first = cutAfter[0]
-    removals.push([first.index!, code.length])
+      removals.push([startIdx, idx + line.length + 1])
+    }
+
+    lineIndex++
+    idx += line.length + 1
   }
-  if (cutStart.length !== cutEnd.length) {
+
+  if (cutStarts.length > 0) {
     throw new TwoslashError(
       `Mismatched cut markers`,
-      `You have ${cutStart.length} cut-starts and ${cutEnd.length} cut-ends`,
+      `You have unclosed cut-starts at lines ${cutStarts.join(', ')}`,
       `Make sure you have a matching pair for each.`,
     )
   }
-  for (let i = 0; i < cutStart.length; i++) {
-    const start = cutStart[i]
-    const end = cutEnd[i]
-    if (start.index! > end.index!) {
-      throw new TwoslashError(
-        `Mismatched cut markers`,
-        `You have a cut-start at ${start.index} which is after the cut-end at ${end.index}`,
-        `Make sure you have a matching pair for each.`,
-      )
-    }
-    removals.push([start.index!, end.index! + end[0].length])
-  }
 
   if (meta)
     meta.removals.push(...removals)

packages/twoslash/test/cutting.test.ts

@@ -140,3 +140,10 @@ describe('supports space before cut comments', () => {
     expect(hover1?.line).toEqual(hover2?.line)
   })
 })
+
+describe('supports cut comments at end of file', () => {
+  const file1 = `const x = "123"\n// ---cut-start---\n  /** @type {"345"} */\n// ---cut-end---`
+  it('works without error', () => {
+    twoslasher(file1, 'ts')
+  })
+})