Decaff helper jscodemods. (#5732)

* Added a file that removes comments that start with #.

* Added .eslintrc to silence ts errors in codemods.

* Convert switch (false) to if-else.

* Add disable-eslint no-empty by default after empty catch.

* Reserve comments when converting switch-case.

* Added new codemods to bulk-decaffeinate.

* Preserve comments.

* Ignored lint rules for test fixtures.

* Move comments between arrow and block to the top.

* Merged tests into one file.

* Turned off no-undef for test fixtures.

* No-cond-assign

* Added jscodemods to decaff config.

* Fixed typo.

* Make CI test codemods

* Added test-no-return.

* Revert "Added test-no-return."

This reverts commit d610829e957e38a6d56c19ba2219681e3f6c65ec.

* fix arrow-comment


Co-authored-by: Ben Kucera <14625260+Bkucera@users.noreply.github.com>
Co-authored-by: Zach Bloomquist <github@chary.us>

scripts/decaff/.eslintrc.json

@@ -0,0 +1,3 @@
+{
+  "parser": "espree"
+}

scripts/decaff/__testfixtures__/.eslintrc.json

@@ -0,0 +1,11 @@
+{
+  "parser": "espree",
+  "rules": {
+    "no-empty": "off",
+    "no-undef": "off",
+    "no-cond-assign": "off",
+    "semi": "off",
+    "brace-style": "off",
+    "no-case-declarations": "off"
+  }
+}

scripts/decaff/__testfixtures__/arrow-comment.input.js

@@ -0,0 +1,10 @@
+// Original comment
+const func = (a, b) =>
+// Multiline comment
+// is here
+{
+  a.works()
+  b.check.thisOut()
+}
+
+func()

scripts/decaff/__testfixtures__/arrow-comment.output.js

@@ -0,0 +1,10 @@
+// Original comment
+// Multiline comment
+// is here
+const func = (a, b) =>
+{
+  a.works()
+  b.check.thisOut()
+};
+
+func()

scripts/decaff/__testfixtures__/empty-catch.input.js

@@ -0,0 +1,7 @@
+try {
+  // do something
+} catch (e) {}
+
+try {
+  // do something
+} finally {}

scripts/decaff/__testfixtures__/empty-catch.output.js

@@ -0,0 +1,7 @@
+try {
+  // do something
+} catch (e) {} // eslint-disable-line no-empty
+
+try {
+  // do something
+} finally {}

scripts/decaff/__testfixtures__/no-cond-assign.input.js

@@ -0,0 +1,6 @@
+let a
+
+// Comment
+if (a = c()) {
+  a.fix()
+}

scripts/decaff/__testfixtures__/no-cond-assign.output.js

@@ -0,0 +1,8 @@
+let a
+
+// Comment
+a = c();
+
+if (a) {
+  a.fix()
+}

scripts/decaff/__testfixtures__/remove-comment-sharp.input.js

@@ -0,0 +1,6 @@
+//# Testing this
+// eslint-disable-next-line
+console.log('it works') //# Test
+
+// This # should not be removed.
+/*# it's not wrong */

scripts/decaff/__testfixtures__/remove-comment-sharp.output.js

@@ -0,0 +1,6 @@
+// Testing this
+// eslint-disable-next-line
+console.log('it works') // Test
+
+// This # should not be removed.
+/*# it's not wrong */

scripts/decaff/__testfixtures__/switch-false.input.js

@@ -0,0 +1,33 @@
+function f () {
+  switch (false) {
+    // Comment should be reserved
+    case !a.subject(a):
+      let x = 30
+
+      b.doSomething(x)
+      break
+    // Multi line comment
+    // should be reserved
+    case c.isGood:
+      c.checkThisOut()
+      findThings()
+      break
+    case isBad:
+      c.neverCheck()
+      break
+    case !isAwesome:
+      a.subject(a)
+      break
+    case hi:
+      // This should be reserved, too
+      return 3
+    case you:
+      // This comment is preserved
+      break
+    default:
+      b.goToNext()
+      break
+  }
+}
+
+f()

scripts/decaff/__testfixtures__/switch-false.output.js

@@ -0,0 +1,25 @@
+function f () {
+  if (a.subject(a)) {
+    // Comment should be reserved
+    let x = 30;
+
+    b.doSomething(x)
+  } else if (!c.isGood) {
+    // Multi line comment
+    // should be reserved
+    c.checkThisOut();
+    findThings()
+  } else if (!isBad) {
+    c.neverCheck();
+  } else if (isAwesome) {
+    a.subject(a);
+  } else if (!hi) {
+    // This should be reserved, too
+    return 3
+  } else if (!you) // This comment is preserved
+  {} else {
+    b.goToNext();
+  }
+}
+
+f()

scripts/decaff/__tests__/decaff.test.js

@@ -0,0 +1,10 @@
+/* global jest */
+
+jest.autoMockOff()
+const defineTest = require('jscodeshift/dist/testUtils').defineTest
+
+defineTest(__dirname, 'switch-false')
+defineTest(__dirname, 'empty-catch')
+defineTest(__dirname, 'remove-comment-sharp')
+defineTest(__dirname, 'arrow-comment')
+defineTest(__dirname, 'no-cond-assign')

scripts/decaff/arrow-comment.js

@@ -0,0 +1,28 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.VariableDeclaration, {
+    declarations: [{
+      type: 'VariableDeclarator',
+      init: {
+        type: 'ArrowFunctionExpression',
+        body: {
+          type: 'BlockStatement',
+        },
+      },
+    }],
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+    const comments = node.declarations[0].init.body.comments
+
+    if (comments && comments.length > 0) {
+      node.comments = [...node.comments, ...comments]
+      node.declarations[0].init.body.comments = null
+    }
+
+    return node
+  })
+  .toSource()
+}

scripts/decaff/empty-catch.js

@@ -0,0 +1,28 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  const source = j(fileInfo.source)
+  .find(j.TryStatement)
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    // Add trailing eslint-disable-line for empty catch block
+    if (node.handler && node.handler.body.body.length === 0) {
+      node.handler.body.comments = [
+        {
+          type: 'Line',
+          value: ' eslint-disable-line no-empty',
+          leading: false,
+          trailing: true,
+        },
+      ]
+    }
+
+    return node
+  })
+  .toSource()
+
+  // Generated source above creates {}// eslint-disable-line block.
+  // So, add a space with replace
+  return source.replace(/\{\}\/\/ eslint-disable-line/g, '{} // eslint-disable-line')
+}

scripts/decaff/no-cond-assign.js

@@ -0,0 +1,29 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.IfStatement, {
+    test: {
+      type: 'AssignmentExpression',
+    },
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    const assign = j.expressionStatement(node.test)
+
+    assign.comments = node.comments
+
+    const ifStatement = j.ifStatement(
+      node.test.left,
+      node.consequent,
+      node.alternate
+    )
+
+    return [
+      assign,
+      ifStatement,
+    ]
+  })
+  .toSource()
+}

scripts/decaff/remove-comment-sharp.js

@@ -0,0 +1,4 @@
+// This file doesn't use AST because it makes things too complicated.
+module.exports = (fileInfo) => {
+  return fileInfo.source.replace(/\/\/#/g, '//')
+}

scripts/decaff/switch-false.js

@@ -0,0 +1,98 @@
+module.exports = (fileInfo, api) => {
+  const j = api.jscodeshift
+
+  return j(fileInfo.source)
+  .find(j.SwitchStatement, {
+    discriminant: {
+      type: 'Literal',
+      value: false,
+    },
+  })
+  .replaceWith((nodePath) => {
+    const { node } = nodePath
+
+    const cases = node.cases.map((c) => {
+      const { test, consequent, comments } = c
+
+      return {
+        test: generateTest(j, test),
+        content: generateContent(j, consequent),
+        comments,
+      }
+    })
+
+    const ifStatement = generateIfStatement(j, cases)
+
+    ifStatement.comments = node.comments
+
+    return ifStatement
+  })
+  .toSource()
+}
+
+function generateTest (j, test) {
+  if (test) {
+    if (test.type === 'UnaryExpression') {
+      return test.argument
+    }
+
+    return j.unaryExpression('!', test)
+  }
+
+  return null
+}
+
+function generateContent (j, consequent) {
+  if (consequent.length === 1 && consequent[0].type === 'BreakStatement') {
+    const block = j.blockStatement([])
+
+    block.comments = consequent[0].comments
+
+    return block
+  }
+
+  return j.blockStatement(consequent.filter((c) => c.type !== 'BreakStatement'))
+}
+
+function generateIfStatement (j, cases) {
+  const nonDefaultCases = cases.filter((c) => c.test !== null)
+  const defaultCase = cases.filter((c) => c.test === null)[0]
+
+  let ifStatement = null
+
+  if (defaultCase) {
+    const content = addComment(defaultCase.content, defaultCase.comments)
+
+    ifStatement = content
+  }
+
+  nonDefaultCases.reverse().forEach((c) => {
+    const content = addComment(c.content, c.comments)
+
+    ifStatement = j.ifStatement(
+      c.test,
+      content,
+      ifStatement
+    )
+  })
+
+  return ifStatement
+}
+
+function addComment (content, comments) {
+  if (content.body.length > 0) {
+    content.body[0].comments = [...(comments || []), ...(content.body[0].comments || [])]
+  } else {
+    const newComments = (comments || []).map((co) => {
+      return {
+        ...co,
+        leading: false,
+        trailing: false,
+      }
+    })
+
+    content.comments = [...newComments, ...(content.comments || [])]
+  }
+
+  return content
+}