refactor newlineBeforeReturn to support more variants

src/rules/newlineRule.ts

@@ -0,0 +1,150 @@
+/**
+* @license
+* Copyright 2017 Palantir Technologies, Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*     http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+import { getPreviousStatement, isBlock, isClassDeclaration, isFunctionWithBody, getChildOfKind } from "tsutils";
+import * as ts from "typescript";
+import * as Lint from "../index";
+
+enum OptionState {
+    always = "always",
+    ignore = "ignore",
+    never = "never",
+}
+
+const ALWAYS_IGNORE_OR_NEVER = {
+    enum: OptionState,
+    type: "string",
+};
+
+type OptionName = "return" | "class" | "functionBlock" | "block";
+const optionNames: OptionName[] = ["return", "class", "functionBlock", "block"];
+type Option = "always" | "ignore" | "never";
+type Options = Partial<Record<OptionName, Option>>;
+
+function parseOptions(json: Option | Options | undefined): Options {
+    const options: Options = { };
+    for (const optionName of optionNames) {
+        options[optionName] = typeof json === "object" ? json[optionName] : json === undefined ? "always" : json;
+    }
+    return options;
+}
+
+export class Rule extends Lint.Rules.AbstractRule {
+    /* tslint:disable:object-literal-sort-keys */
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: "newline",
+        description: "Requires or disallows blank lines before return, after class declaration, function block declaration or block.",
+        rationale: "Helps maintain a readable style in your codebase.",
+        optionsDescription: Lint.Utils.dedent`
+            Following arguments may be optionally provided:
+ 
+            * \`"return"\` checks for empty line before return when not the only line in the block.
+            * \`"class"\` checks for empty line after class declaration.
+            * \`"functionBlock"\` checks for empty line after function block declaration.
+            * \`"block"\` checks for empty line after block declaration.`,
+        options: {
+            properties: {
+                return: ALWAYS_IGNORE_OR_NEVER,
+                class: ALWAYS_IGNORE_OR_NEVER,
+                functionBlock: ALWAYS_IGNORE_OR_NEVER,
+                block: ALWAYS_IGNORE_OR_NEVER,
+            },
+            type: "object",
+        },
+        optionExamples: [[true, {return: "always", class: "never"}]],
+        type: "style",
+        typescriptOnly: false,
+    };
+    /* tslint:enable:object-literal-sort-keys */
+
+    public static FAILURE_STRING_FACTORY(kind: boolean, nodeType: string) {
+        const kindMsg = kind ? 'Missing' : 'Unneeded';
+        return `${kindMsg} blank line before ${nodeType}`;
+    }
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithWalker(new NewlineWalker(sourceFile, this.ruleName, parseOptions(this.ruleArguments[0] as Option | Options | undefined)));
+    }
+}
+
+class NewlineWalker extends Lint.AbstractWalker<Options> {
+    public walk(sourceFile: ts.SourceFile) {
+        const cb = (node: ts.Node): void => {
+            if (node.kind === ts.SyntaxKind.ReturnStatement && this.options.return != OptionState.ignore) {
+                const prev = getPreviousStatement(node as ts.Statement);
+                if (prev === undefined) {
+                    // return is not within a block (e.g. the only child of an IfStatement) or the first statement of the block
+                    // no need to check for preceding newline
+                    return;
+                }
+
+                this.checkForEmptyLine(prev, node, this.options.return == OptionState.always, 'return');
+            }
+
+            if (isClassDeclaration(node) && this.options.class != OptionState.ignore) {
+                this.checkForEmptyLine(
+                    getChildOfKind(node, ts.SyntaxKind.OpenBraceToken, this.sourceFile)!, node.members[0],
+                    this.options.class == OptionState.always, 'first member',
+                );
+            }
+
+            if (isBlock(node) &&
+                    (isFunctionWithBody(node.parent!) && this.options.functionBlock != OptionState.ignore
+                        || this.options.block != OptionState.ignore)) {
+                this.checkForEmptyLine(
+                    node.getChildAt(0), node.statements[0], this.options.functionBlock == OptionState.always, 'first statement',
+                );
+            }
+            return ts.forEachChild(node, cb);
+        };
+        return ts.forEachChild(sourceFile, cb);
+    }
+
+    private checkForEmptyLine(node: ts.Node, firstNode: ts.Node, lineRequired: boolean, nodeType: string) {
+        let start = node.end;
+        let line = ts.getLineAndCharacterOfPosition(this.sourceFile, start).line;
+        let firstNodeStart = firstNode.getStart();
+        let firstLine = ts.getLineAndCharacterOfPosition(this.sourceFile, firstNodeStart).line;
+        const comments = ts.getLeadingCommentRanges(this.sourceFile.text, firstNode.pos);
+
+        if (comments !== undefined) {
+            // check for blank lines between comments
+            for (let i = comments.length - 1; i >= 0; --i) {
+                const endLine = ts.getLineAndCharacterOfPosition(this.sourceFile, comments[i].end).line;
+                if (endLine < firstLine - 1) {
+                    // found empty line between nodes
+                    start = comments[i].end;
+                    firstLine = ts.getLineAndCharacterOfPosition(this.sourceFile, firstNodeStart).line;
+                    break;
+                }
+
+                firstNodeStart = comments[i].pos;
+                firstLine = ts.getLineAndCharacterOfPosition(this.sourceFile, firstNodeStart).line;
+            }
+        }
+
+        if (!lineRequired && line + 1 < firstLine) {
+            this.addFailure(
+                start + 1, ts.getPositionOfLineAndCharacter(this.sourceFile, firstLine, 0) - 1,
+                Rule.FAILURE_STRING_FACTORY(lineRequired, nodeType)
+            );
+        } else if (lineRequired && line + 1 == firstLine) {
+            const pos = ts.getPositionOfLineAndCharacter(this.sourceFile, firstLine, 0);
+            this.addFailure(pos, pos, Rule.FAILURE_STRING_FACTORY(lineRequired, nodeType));
+        }
+    }
+}