Script for fixing non-null assertions

fix-non-null-assertions.ts

import * as fs from 'fs';
import * as ts from 'typescript';
import glob from 'glob';
import { sortBy, uniq } from 'lodash';

/**
 * Inserts the specified `text` at the specified `line` and `character` in the file at `filepath`.
 */
const insertTextAtLine = (opts: {
  filepath: string;
  line: number;
  text: string;
}) => {
  const contents = fs.readFileSync(opts.filepath, 'utf8');
  const lines = contents.split('\n');

  const modified = [
    ...lines.slice(0, opts.line),
    opts.text,
    ...lines.slice(opts.line),
  ];

  fs.writeFileSync(opts.filepath, modified.join('\n'));
};

function isLocationInJSX(opts: {
  filepath: string;
  contents: string;
  line: number;
  character: number;
}): boolean {
  const sourceFile = ts.createSourceFile(
    opts.filepath,
    opts.contents,
    ts.ScriptTarget.Latest,
    true,
    ts.ScriptKind.TSX,
  );

  const position = ts.getPositionOfLineAndCharacter(
    sourceFile,
    opts.line,
    opts.character,
  );
  const node = findNodeAtPosition(sourceFile, position);
  return isJSXNode(node);
}

function findNodeAtPosition(
  sourceFile: ts.SourceFile,
  position: number,
): ts.Node | undefined {
  function visit(node: ts.Node): ts.Node | undefined {
    if (position >= node.getStart() && position < node.getEnd()) {
      return ts.forEachChild(node, visit) || node;
    }
  }
  return visit(sourceFile);
}

function isJSXNode(node: ts.Node | undefined): boolean {
  if (!node) return false;

  if (
    ts.isJsxElement(node) ||
    ts.isJsxFragment(node) ||
    ts.isJsxText(node) ||
    (ts.isJsxExpression(node) && !ts.isJsxAttribute(node.parent))
  ) {
    return true;
  }
  return false;
}

const files = glob.sync(`${__dirname}/src/**/*.ts{,x}`);

const program = ts.createProgram(files, {
  lib: ['dom', 'es2015', 'es2016.array.include', 'ES2019.Array'],
  outDir: './dist',
  rootDir: '.',
  baseUrl: '.',
  noImplicitAny: false,
  strictNullChecks: true,
  module: ts.ModuleKind.ES2020,
  noUnusedParameters: true,
  allowSyntheticDefaultImports: true,
  esModuleInterop: true,
  noImplicitThis: true,
  alwaysStrict: true,
  strictFunctionTypes: true,
  moduleResolution: ts.ModuleResolutionKind.NodeJs,
  pretty: true,
  inlineSourceMap: true,
  inlineSources: true,
  jsx: ts.JsxEmit.React,
  target: ts.ScriptTarget.ES2020,
  skipLibCheck: true,
  resolveJsonModule: true,
  noUnusedLocals: false,
  allowJs: true,
  noEmit: true,
});

const emitResult = program.emit();

const diagnostics = ts
  .getPreEmitDiagnostics(program)
  .concat(emitResult.diagnostics);

console.log('DIAGNOSTICS: ', diagnostics.length);

// map of filename -> line, char of errors
const errorLocations: Record<string, [number, number][]> = {};

for (const diag of diagnostics) {
  if (!diag.file) {
    continue;
  }

  if (diag.category !== ts.DiagnosticCategory.Error) {
    console.log('Skipping non-error diagnostic');
    continue;
  }

  // This is "could not find a declaration file"
  if (diag.code === 7016) {
    continue;
  }

  // This is "implicit any"
  if (diag.code === 7006) {
    continue;
  }

  if (diag.code === 2739) {
    continue;
  }

  const { line, character } = ts.getLineAndCharacterOfPosition(
    diag.file,
    diag.start!,
  );

  if (!errorLocations[diag.file.fileName]) {
    errorLocations[diag.file.fileName] = [];
  }

  errorLocations[diag.file.fileName].push([line, character]);
}

for (const [filepath, locations] of Object.entries(errorLocations)) {
  const lines = sortBy(uniq(locations.map(([line]) => line))).reverse();
  const contents = fs.readFileSync(filepath, 'utf8');

  for (const line of lines) {
    if (
      filepath.includes('.tsx') &&
      isLocationInJSX({ filepath, contents, line, character: 0 })
    ) {
      insertTextAtLine({
        filepath,
        line,
        text: '{/* @ts-expect-error This directive was added as part of a bulk-change to enable strictNullChecks. */}',
      });
    } else {
      insertTextAtLine({
        filepath,
        line,
        text: '// @ts-expect-error This directive was added as part of a bulk-change to enable strictNullChecks.',
      });
    }
  }
}