Jasmine/Jest v20+: this syntax codemod

Closes #57

Context: jestjs/jest#3553

src/cli/index.js

@@ -42,6 +42,7 @@ const TRANSFORMER_CHAI_SHOULD = 'chai-should';
 const TRANSFORMER_MOCHA = 'mocha';
 const TRANSFORMER_SHOULD = 'should';
 const TRANSFORMER_TAPE = 'tape';
+const TRANSFORMER_JASMINE_THIS = 'jasmine-this';
 
 const ALL_TRANSFORMERS = [
     TRANSFORMER_AVA,
@@ -50,6 +51,7 @@ const ALL_TRANSFORMERS = [
     // TODO: waiting for expect@20+ release: TRANSFORMER_EXPECT,
     TRANSFORMER_MOCHA,
     TRANSFORMER_TAPE,
+    TRANSFORMER_JASMINE_THIS,
 ];
 
 function supportFailure(supportedItems) {
@@ -85,6 +87,10 @@ inquirer
                     value: TRANSFORMER_EXPECT,
                 },
                 */
+                {
+                    name: 'Jasmine: this usage',
+                    value: TRANSFORMER_JASMINE_THIS,
+                },
                 {
                     name: 'Mocha',
                     value: TRANSFORMER_MOCHA,

src/transformers/jasmine-this.js

@@ -0,0 +1,200 @@
+/**
+ * Codemod for transforming Jasmine `this` context into Jest v20+ compatible syntax.
+ */
+
+import finale from '../utils/finale';
+
+const testFunctionNames = ['after', 'afterEach', 'before', 'beforeEach', 'it', 'test'];
+const allFunctionNames = ['describe'].concat(testFunctionNames);
+const ignoredIdentifiers = ['retries', 'skip', 'slow', 'timeout'];
+
+function isFunctionExpressionWithinSpecificFunctions(path, acceptedFunctionNames) {
+    if (!path || !path.parentPath || !Array.isArray(path.parentPath.value)) {
+        return false;
+    }
+
+    const callExpressionPath = path.parentPath.parentPath;
+
+    return (
+        !!callExpressionPath &&
+        !!callExpressionPath.value &&
+        callExpressionPath.value.callee.type === 'Identifier' &&
+        acceptedFunctionNames.indexOf(callExpressionPath.value.callee.name) > -1
+    );
+}
+
+function isWithinObjectOrClass(path) {
+    const invalidParentTypes = ['Property', 'MethodDefinition'];
+    let currentPath = path;
+
+    while (
+        currentPath &&
+        currentPath.value &&
+        invalidParentTypes.indexOf(currentPath.value.type) === -1
+    ) {
+        currentPath = currentPath.parentPath;
+    }
+    return currentPath ? invalidParentTypes.indexOf(currentPath.value.type) > -1 : false;
+}
+
+function isWithinSpecificFunctions(path, acceptedFunctionNames, matchAll) {
+    if (!matchAll) {
+        // Do not replace within functions declared as object properties or class methods
+        // See `transforms plain functions within lifecycle methods` test
+        if (isWithinObjectOrClass(path)) {
+            return false;
+        }
+    }
+    let currentPath = path;
+
+    while (
+        currentPath &&
+        currentPath.value &&
+        currentPath.value.type !== 'FunctionExpression'
+    ) {
+        currentPath = currentPath.parentPath;
+    }
+
+    return (
+        isFunctionExpressionWithinSpecificFunctions(currentPath, acceptedFunctionNames) ||
+        (currentPath
+            ? isWithinSpecificFunctions(currentPath.parentPath, testFunctionNames, false)
+            : false)
+    );
+}
+
+export default function jasmineThis(fileInfo, api, options) {
+    const j = api.jscodeshift;
+    const root = j(fileInfo.source);
+
+    const getValidThisExpressions = node => {
+        return j(node)
+            .find(j.MemberExpression, {
+                object: {
+                    type: j.ThisExpression.name,
+                },
+                property: {
+                    name: name => ignoredIdentifiers.indexOf(name) === -1,
+                },
+            })
+            .filter(path => isWithinSpecificFunctions(path, allFunctionNames, true));
+    };
+
+    const mutateScope = (ast, body) => {
+        const replacedIdentifiersMap = {};
+
+        const updateThisExpressions = () => {
+            return ast
+                .find(j.MemberExpression)
+                .filter(path => path.value.object.type === 'ThisExpression')
+                .filter(path => isWithinSpecificFunctions(path, allFunctionNames, true))
+                .replaceWith(replaceThisExpression)
+                .size();
+        };
+
+        const replaceThisExpression = path => {
+            const originalName = path.value.property.name;
+            const newName = originalName + 'Context';
+            replacedIdentifiersMap[originalName] = newName;
+            return j.identifier(newName);
+        };
+
+        const addLetDeclarations = () => {
+            Object.keys(replacedIdentifiersMap)
+                // Reverse the keys because we're adding them one by one to the front of the body array
+                .sort()
+                .reverse()
+                .forEach(originalName => {
+                    body.unshift(
+                        j.variableDeclaration('let', [
+                            j.variableDeclarator(
+                                j.identifier(replacedIdentifiersMap[originalName]),
+                                null
+                            ),
+                        ])
+                    );
+                });
+        };
+
+        updateThisExpressions();
+        addLetDeclarations();
+    };
+
+    const mutateDescribe = path => {
+        const functionExpression = path.value.arguments.find(
+            node =>
+                node.type === 'FunctionExpression' ||
+                node.type === 'ArrowFunctionExpression'
+        );
+        const functionBody = functionExpression.body;
+        const ast = j(functionBody);
+
+        mutateScope(ast, functionBody.body);
+    };
+
+    const updateRoot = () => {
+        const topLevelLifecycleMethods = root
+            .find(j.CallExpression, {
+                callee: {
+                    type: j.Identifier.name,
+                    name: name => testFunctionNames.indexOf(name) > -1,
+                },
+            })
+            // Find only lifecyle methods which are in the root scope
+            .filter(
+                path =>
+                    path.parentPath.value.type === j.ExpressionStatement.name &&
+                    Array.isArray(path.parentPath.parentPath.value) &&
+                    path.parentPath.parentPath.parentPath.value.type === j.Program.name
+            )
+            .filter(path => getValidThisExpressions(path.value).size() > 0)
+            .size();
+
+        if (topLevelLifecycleMethods > 0) {
+            const path = root.get();
+            mutateScope(root, path.value.program.body);
+            return 1;
+        }
+
+        return 0;
+    };
+
+    const updateDescribes = () => {
+        return root
+            .find(j.CallExpression, {
+                callee: {
+                    type: j.Identifier.name,
+                    name: 'describe',
+                },
+            })
+            .filter(path => getValidThisExpressions(path.value).size() > 0)
+            .forEach(mutateDescribe)
+            .size();
+    };
+
+    const updateFunctionExpressions = () => {
+        return root
+            .find(j.FunctionExpression)
+            .filter(path =>
+                isFunctionExpressionWithinSpecificFunctions(path, allFunctionNames)
+            )
+            .replaceWith(path => {
+                const newFn = j.arrowFunctionExpression(
+                    path.value.params,
+                    path.value.body,
+                    path.value.expression
+                );
+                newFn.async = path.value.async;
+                return newFn;
+            })
+            .size();
+    };
+
+    const mutations = updateRoot() + updateDescribes() + updateFunctionExpressions();
+
+    if (!mutations) {
+        return null;
+    }
+
+    return finale(fileInfo, j, root, options);
+}