From f82b574fd498910c87fbcf03c4fc15afd7acfa2e Mon Sep 17 00:00:00 2001
From: Joseph Frazier <1212jtraceur@gmail.com>
Date: Mon, 18 Dec 2017 12:33:53 -0500
Subject: [PATCH] Return early from `massageAST()` (#3522)

This reduces nesting and handles the edge cases first.

This commit is best viewed ignoring whitespace differences:

    git show -w
---
 src/clean-ast.js | 510 ++++++++++++++++++++++++-----------------------
 1 file changed, 256 insertions(+), 254 deletions(-)

diff --git a/src/clean-ast.js b/src/clean-ast.js
index 9ef279d7d..1913fb83c 100644
--- a/src/clean-ast.js
+++ b/src/clean-ast.js
@@ -8,262 +8,264 @@ function massageAST(ast, parent) {
   if (Array.isArray(ast)) {
     return ast.map(e => massageAST(e, parent)).filter(e => e);
   }
-  if (ast && typeof ast === "object") {
-    // We remove extra `;` and add them when needed
-    if (ast.type === "EmptyStatement") {
-      return undefined;
-    }
 
-    // We move text around, including whitespaces and add {" "}
-    if (ast.type === "JSXText") {
-      return undefined;
-    }
-    if (
-      ast.type === "JSXExpressionContainer" &&
-      ast.expression.type === "Literal" &&
-      ast.expression.value === " "
-    ) {
-      return undefined;
-    }
-
-    const newObj = {};
-    for (const key in ast) {
-      if (typeof ast[key] !== "function") {
-        newObj[key] = massageAST(ast[key], ast);
-      }
-    }
-
-    [
-      "loc",
-      "range",
-      "raw",
-      "comments",
-      "leadingComments",
-      "trailingComments",
-      "extra",
-      "start",
-      "end",
-      "tokens",
-      "flags",
-      "raws",
-      "sourceIndex",
-      "id",
-      "source",
-      "before",
-      "after",
-      "trailingComma",
-      "parent",
-      "prev",
-      "position"
-    ].forEach(name => {
-      delete newObj[name];
-    });
-
-    // for markdown codeblock
-    if (ast.type === "code") {
-      delete newObj.value;
-    }
-    // for markdown whitespace: "\n" and " " are considered the same
-    if (ast.type === "whitespace" && ast.value === "\n") {
-      newObj.value = " ";
-    }
-
-    if (
-      ast.type === "media-query" ||
-      ast.type === "media-query-list" ||
-      ast.type === "media-feature-expression"
-    ) {
-      delete newObj.value;
-    }
-
-    if (ast.type === "css-rule") {
-      delete newObj.params;
-    }
-
-    if (ast.type === "selector-combinator") {
-      newObj.value = newObj.value.replace(/\s+/g, " ");
-    }
-
-    if (ast.type === "media-feature") {
-      newObj.value = newObj.value.replace(/ /g, "");
-    }
-
-    if (
-      (ast.type === "value-word" && ast.isColor && ast.isHex) ||
-      ast.type === "media-feature" ||
-      ast.type === "selector-root-invalid" ||
-      ast.type === "selector-pseudo"
-    ) {
-      newObj.value = newObj.value.toLowerCase();
-    }
-    if (ast.type === "css-decl") {
-      newObj.prop = newObj.prop.toLowerCase();
-    }
-    if (ast.type === "css-atrule" || ast.type === "css-import") {
-      newObj.name = newObj.name.toLowerCase();
-    }
-    if (ast.type === "value-number") {
-      newObj.unit = newObj.unit.toLowerCase();
-    }
-
-    if (
-      (ast.type === "media-feature" ||
-        ast.type === "media-keyword" ||
-        ast.type === "media-type" ||
-        ast.type === "media-unknown" ||
-        ast.type === "media-url" ||
-        ast.type === "media-value" ||
-        ast.type === "selector-root-invalid" ||
-        ast.type === "selector-attribute" ||
-        ast.type === "selector-string" ||
-        ast.type === "selector-class" ||
-        ast.type === "selector-combinator" ||
-        ast.type === "value-string") &&
-      newObj.value
-    ) {
-      newObj.value = cleanCSSStrings(newObj.value);
-    }
-
-    if (ast.type === "css-import" && newObj.importPath) {
-      newObj.importPath = cleanCSSStrings(newObj.importPath);
-    }
-
-    if (ast.type === "selector-attribute" && newObj.value) {
-      newObj.value = newObj.value.replace(/^['"]|['"]$/g, "");
-      delete newObj.quoted;
-    }
-
-    if (
-      (ast.type === "media-value" ||
-        ast.type === "media-type" ||
-        ast.type === "value-number" ||
-        ast.type === "selector-root-invalid" ||
-        ast.type === "selector-class" ||
-        ast.type === "selector-combinator" ||
-        ast.type === "selector-tag") &&
-      newObj.value
-    ) {
-      newObj.value = newObj.value.replace(
-        /([\d.eE+-]+)([a-zA-Z]*)/g,
-        (match, numStr, unit) => {
-          const num = Number(numStr);
-          return isNaN(num) ? match : num + unit.toLowerCase();
-        }
-      );
-    }
-
-    // (TypeScript) Ignore `static` in `constructor(static p) {}`
-    // and `export` in `constructor(export p) {}`
-    if (
-      ast.type === "TSParameterProperty" &&
-      ast.accessibility === null &&
-      !ast.readonly
-    ) {
-      return {
-        type: "Identifier",
-        name: ast.parameter.name,
-        typeAnnotation: newObj.parameter.typeAnnotation,
-        decorators: newObj.decorators
-      };
-    }
-
-    // (TypeScript) ignore empty `specifiers` array
-    if (
-      ast.type === "TSNamespaceExportDeclaration" &&
-      ast.specifiers &&
-      ast.specifiers.length === 0
-    ) {
-      delete newObj.specifiers;
-    }
-
-    // (TypeScript) bypass TSParenthesizedType
-    if (
-      ast.type === "TSParenthesizedType" &&
-      ast.typeAnnotation.type === "TSTypeAnnotation"
-    ) {
-      return newObj.typeAnnotation.typeAnnotation;
-    }
-
-    // We convert <div></div> to <div />
-    if (ast.type === "JSXOpeningElement") {
-      delete newObj.selfClosing;
-    }
-    if (ast.type === "JSXElement") {
-      delete newObj.closingElement;
-    }
-
-    // We change {'key': value} into {key: value}
-    if (
-      (ast.type === "Property" ||
-        ast.type === "MethodDefinition" ||
-        ast.type === "ClassProperty" ||
-        ast.type === "TSPropertySignature" ||
-        ast.type === "ObjectTypeProperty") &&
-      typeof ast.key === "object" &&
-      ast.key &&
-      (ast.key.type === "Literal" || ast.key.type === "Identifier")
-    ) {
-      delete newObj.key;
-    }
-
-    // Remove raw and cooked values from TemplateElement when it's CSS
-    // styled-jsx
-    if (
-      ast.type === "JSXElement" &&
-      ast.openingElement.name.name === "style" &&
-      ast.openingElement.attributes.some(attr => attr.name.name === "jsx")
-    ) {
-      const templateLiterals = newObj.children
-        .filter(
-          child =>
-            child.type === "JSXExpressionContainer" &&
-            child.expression.type === "TemplateLiteral"
-        )
-        .map(container => container.expression);
-
-      const quasis = templateLiterals.reduce(
-        (quasis, templateLiteral) => quasis.concat(templateLiteral.quasis),
-        []
-      );
-
-      quasis.forEach(q => delete q.value);
-    }
-
-    // CSS template literals in css prop
-    if (
-      ast.type === "JSXAttribute" &&
-      ast.name.name === "css" &&
-      ast.value.type === "JSXExpressionContainer" &&
-      ast.value.expression.type === "TemplateLiteral"
-    ) {
-      newObj.value.expression.quasis.forEach(q => delete q.value);
-    }
-
-    // styled-components, graphql, markdown
-    if (
-      ast.type === "TaggedTemplateExpression" &&
-      (ast.tag.type === "MemberExpression" ||
-        (ast.tag.type === "Identifier" &&
-          (ast.tag.name === "gql" ||
-            ast.tag.name === "graphql" ||
-            ast.tag.name === "css" ||
-            ast.tag.name === "md" ||
-            ast.tag.name === "markdown")) ||
-        ast.tag.type === "CallExpression")
-    ) {
-      newObj.quasi.quasis.forEach(quasi => delete quasi.value);
-    }
-    if (
-      ast.type === "TemplateLiteral" &&
-      parent.type === "CallExpression" &&
-      parent.callee.name === "graphql"
-    ) {
-      newObj.quasis.forEach(quasi => delete quasi.value);
-    }
-
-    return newObj;
+  if (!ast || typeof ast !== "object") {
+    return ast;
   }
-  return ast;
+
+  // We remove extra `;` and add them when needed
+  if (ast.type === "EmptyStatement") {
+    return undefined;
+  }
+
+  // We move text around, including whitespaces and add {" "}
+  if (ast.type === "JSXText") {
+    return undefined;
+  }
+  if (
+    ast.type === "JSXExpressionContainer" &&
+    ast.expression.type === "Literal" &&
+    ast.expression.value === " "
+  ) {
+    return undefined;
+  }
+
+  const newObj = {};
+  for (const key in ast) {
+    if (typeof ast[key] !== "function") {
+      newObj[key] = massageAST(ast[key], ast);
+    }
+  }
+
+  [
+    "loc",
+    "range",
+    "raw",
+    "comments",
+    "leadingComments",
+    "trailingComments",
+    "extra",
+    "start",
+    "end",
+    "tokens",
+    "flags",
+    "raws",
+    "sourceIndex",
+    "id",
+    "source",
+    "before",
+    "after",
+    "trailingComma",
+    "parent",
+    "prev",
+    "position"
+  ].forEach(name => {
+    delete newObj[name];
+  });
+
+  // for markdown codeblock
+  if (ast.type === "code") {
+    delete newObj.value;
+  }
+  // for markdown whitespace: "\n" and " " are considered the same
+  if (ast.type === "whitespace" && ast.value === "\n") {
+    newObj.value = " ";
+  }
+
+  if (
+    ast.type === "media-query" ||
+    ast.type === "media-query-list" ||
+    ast.type === "media-feature-expression"
+  ) {
+    delete newObj.value;
+  }
+
+  if (ast.type === "css-rule") {
+    delete newObj.params;
+  }
+
+  if (ast.type === "selector-combinator") {
+    newObj.value = newObj.value.replace(/\s+/g, " ");
+  }
+
+  if (ast.type === "media-feature") {
+    newObj.value = newObj.value.replace(/ /g, "");
+  }
+
+  if (
+    (ast.type === "value-word" && ast.isColor && ast.isHex) ||
+    ast.type === "media-feature" ||
+    ast.type === "selector-root-invalid" ||
+    ast.type === "selector-pseudo"
+  ) {
+    newObj.value = newObj.value.toLowerCase();
+  }
+  if (ast.type === "css-decl") {
+    newObj.prop = newObj.prop.toLowerCase();
+  }
+  if (ast.type === "css-atrule" || ast.type === "css-import") {
+    newObj.name = newObj.name.toLowerCase();
+  }
+  if (ast.type === "value-number") {
+    newObj.unit = newObj.unit.toLowerCase();
+  }
+
+  if (
+    (ast.type === "media-feature" ||
+      ast.type === "media-keyword" ||
+      ast.type === "media-type" ||
+      ast.type === "media-unknown" ||
+      ast.type === "media-url" ||
+      ast.type === "media-value" ||
+      ast.type === "selector-root-invalid" ||
+      ast.type === "selector-attribute" ||
+      ast.type === "selector-string" ||
+      ast.type === "selector-class" ||
+      ast.type === "selector-combinator" ||
+      ast.type === "value-string") &&
+    newObj.value
+  ) {
+    newObj.value = cleanCSSStrings(newObj.value);
+  }
+
+  if (ast.type === "css-import" && newObj.importPath) {
+    newObj.importPath = cleanCSSStrings(newObj.importPath);
+  }
+
+  if (ast.type === "selector-attribute" && newObj.value) {
+    newObj.value = newObj.value.replace(/^['"]|['"]$/g, "");
+    delete newObj.quoted;
+  }
+
+  if (
+    (ast.type === "media-value" ||
+      ast.type === "media-type" ||
+      ast.type === "value-number" ||
+      ast.type === "selector-root-invalid" ||
+      ast.type === "selector-class" ||
+      ast.type === "selector-combinator" ||
+      ast.type === "selector-tag") &&
+    newObj.value
+  ) {
+    newObj.value = newObj.value.replace(
+      /([\d.eE+-]+)([a-zA-Z]*)/g,
+      (match, numStr, unit) => {
+        const num = Number(numStr);
+        return isNaN(num) ? match : num + unit.toLowerCase();
+      }
+    );
+  }
+
+  // (TypeScript) Ignore `static` in `constructor(static p) {}`
+  // and `export` in `constructor(export p) {}`
+  if (
+    ast.type === "TSParameterProperty" &&
+    ast.accessibility === null &&
+    !ast.readonly
+  ) {
+    return {
+      type: "Identifier",
+      name: ast.parameter.name,
+      typeAnnotation: newObj.parameter.typeAnnotation,
+      decorators: newObj.decorators
+    };
+  }
+
+  // (TypeScript) ignore empty `specifiers` array
+  if (
+    ast.type === "TSNamespaceExportDeclaration" &&
+    ast.specifiers &&
+    ast.specifiers.length === 0
+  ) {
+    delete newObj.specifiers;
+  }
+
+  // (TypeScript) bypass TSParenthesizedType
+  if (
+    ast.type === "TSParenthesizedType" &&
+    ast.typeAnnotation.type === "TSTypeAnnotation"
+  ) {
+    return newObj.typeAnnotation.typeAnnotation;
+  }
+
+  // We convert <div></div> to <div />
+  if (ast.type === "JSXOpeningElement") {
+    delete newObj.selfClosing;
+  }
+  if (ast.type === "JSXElement") {
+    delete newObj.closingElement;
+  }
+
+  // We change {'key': value} into {key: value}
+  if (
+    (ast.type === "Property" ||
+      ast.type === "MethodDefinition" ||
+      ast.type === "ClassProperty" ||
+      ast.type === "TSPropertySignature" ||
+      ast.type === "ObjectTypeProperty") &&
+    typeof ast.key === "object" &&
+    ast.key &&
+    (ast.key.type === "Literal" || ast.key.type === "Identifier")
+  ) {
+    delete newObj.key;
+  }
+
+  // Remove raw and cooked values from TemplateElement when it's CSS
+  // styled-jsx
+  if (
+    ast.type === "JSXElement" &&
+    ast.openingElement.name.name === "style" &&
+    ast.openingElement.attributes.some(attr => attr.name.name === "jsx")
+  ) {
+    const templateLiterals = newObj.children
+      .filter(
+        child =>
+          child.type === "JSXExpressionContainer" &&
+          child.expression.type === "TemplateLiteral"
+      )
+      .map(container => container.expression);
+
+    const quasis = templateLiterals.reduce(
+      (quasis, templateLiteral) => quasis.concat(templateLiteral.quasis),
+      []
+    );
+
+    quasis.forEach(q => delete q.value);
+  }
+
+  // CSS template literals in css prop
+  if (
+    ast.type === "JSXAttribute" &&
+    ast.name.name === "css" &&
+    ast.value.type === "JSXExpressionContainer" &&
+    ast.value.expression.type === "TemplateLiteral"
+  ) {
+    newObj.value.expression.quasis.forEach(q => delete q.value);
+  }
+
+  // styled-components, graphql, markdown
+  if (
+    ast.type === "TaggedTemplateExpression" &&
+    (ast.tag.type === "MemberExpression" ||
+      (ast.tag.type === "Identifier" &&
+        (ast.tag.name === "gql" ||
+          ast.tag.name === "graphql" ||
+          ast.tag.name === "css" ||
+          ast.tag.name === "md" ||
+          ast.tag.name === "markdown")) ||
+      ast.tag.type === "CallExpression")
+  ) {
+    newObj.quasi.quasis.forEach(quasi => delete quasi.value);
+  }
+  if (
+    ast.type === "TemplateLiteral" &&
+    parent.type === "CallExpression" &&
+    parent.callee.name === "graphql"
+  ) {
+    newObj.quasis.forEach(quasi => delete quasi.value);
+  }
+
+  return newObj;
 }
 
 function cleanCSSStrings(value) {