chore(null): update yarn null:autoadd to run multiple passes (#3346)

#### Description of changes

Previously, if `yarn null:autoadd` added a file to the strictNullChecks config which enabled a previously-ineligible file to be considered for auto-add, you'd have to run `yarn null:autoadd` again and eat the cost of it spinning up a new tsc watch process and rescanning all the already-known-failures.

With this PR, the tool will do this for you automatically, re-using both the watch process and previously-established knowledge of known failures.

`yarn null:progress` update with this PR:

## Web strict-null progress

**42%** complete (**558**/1334 non-test files)

*Contribute at [#2869](#2869). Last update: Fri Sep 11 2020*

#### Pull request checklist
<!-- If a checklist item is not applicable to this change, write "n/a" in the checkbox -->
- [x] Addresses an existing issue: part of #2869
- [x] Ran `yarn fastpass`
- [n/a] Added/updated relevant unit test(s) (and ran `yarn test`)
- [n/a] Verified code coverage for the changes made. Check coverage report at: `<rootDir>/test-results/unit/coverage`
- [x] PR title *AND* final merge commit title both start with a semantic tag (`fix:`, `chore:`, `feat(feature-name):`, `refactor:`). See `CONTRIBUTING.md`.
- [n/a] (UI changes only) Added screenshots/GIFs to description above
- [n/a] (UI changes only) Verified usability with NVDA/JAWS

tools/strict-null-checks/auto-add.js

@@ -14,51 +14,92 @@ const repoRoot = config.repoRoot;
 const tscPath = path.join(repoRoot, 'node_modules', 'typescript', 'bin', 'tsc');
 const tsconfigPath = path.join(repoRoot, config.targetTsconfig);
 
-const buildCompletePattern = /Found (\d+) errors?\. Watching for file changes\./gi;
+async function main() {
+    console.log('## Initializing tsc --watch process...');
+    const tscWatchProcess = child_process.spawn('node', [tscPath, '-p', tsconfigPath, '--watch']);
+    await waitForBuildComplete(tscWatchProcess);
+
+    const alreadyAttempted = new Set();
+
+    for (let pass = 1; ; pass += 1) {
+        let successesThisPass = 0;
+        const uncheckedLeafFiles = await getUncheckedLeafFiles(repoRoot);
+        const candidateFiles = uncheckedLeafFiles.filter(f => !alreadyAttempted.has(f));
+        const candidateCount = candidateFiles.length;
+        console.log(`## Starting pass ${pass} with ${candidateCount} candidate files`);
 
-getUncheckedLeafFiles(repoRoot).then(async files => {
-    const child = child_process.spawn('node', [tscPath, '-p', tsconfigPath, '--watch']);
-    for (const file of files) {
-        await tryAutoAddStrictNulls(child, tsconfigPath, file);
+        for (const file of candidateFiles) {
+            const succeeded = await tryAutoAddStrictNulls(tscWatchProcess, tsconfigPath, file);
+            alreadyAttempted.add(file);
+            if (succeeded) {
+                successesThisPass += 1;
+            }
+        }
+
+        console.log(`### Finished pass ${pass} (added ${successesThisPass}/${candidateCount})`);
+        if (successesThisPass === 0) {
+            break;
+        }
     }
-    child.kill();
 
-    console.log('Collapsing full completed directories into "includes" patterns...');
+    console.log('## Stopping tsc --watch process...');
+    tscWatchProcess.kill();
+
+    console.log('## Collapsing fully null-checked directories into "include" patterns...');
     collapseCompletedDirectories(tsconfigPath);
-});
+}
 
-function tryAutoAddStrictNulls(child, tsconfigPath, file) {
-    return new Promise(resolve => {
-        const relativeFilePath = path.relative(repoRoot, file).replace(/\\/g, '/');
-        console.log(`Trying to auto add '${relativeFilePath}'`);
+async function tryAutoAddStrictNulls(child, tsconfigPath, file) {
+    const relativeFilePath = path.relative(repoRoot, file).replace(/\\/g, '/');
+    console.log(`Trying to auto add '${relativeFilePath}'`);
 
-        const originalConfig = JSON.parse(fs.readFileSync(tsconfigPath).toString());
-        originalConfig.files = Array.from(new Set(originalConfig.files.sort()));
+    const originalConfig = JSON.parse(fs.readFileSync(tsconfigPath).toString());
+    originalConfig.files = Array.from(new Set(originalConfig.files.sort()));
 
-        // Config on accept
-        const newConfig = Object.assign({}, originalConfig);
-        newConfig.files = Array.from(
-            new Set(originalConfig.files.concat('./' + relativeFilePath).sort()),
-        );
+    // Config on accept
+    const newConfig = Object.assign({}, originalConfig);
+    newConfig.files = Array.from(
+        new Set(originalConfig.files.concat('./' + relativeFilePath).sort()),
+    );
 
+    const buildCompetePromise = waitForBuildComplete(child);
+
+    writeTsconfigSync(tsconfigPath, newConfig);
+
+    const errorCount = await buildCompetePromise;
+    const success = errorCount === 0;
+    if (success) {
+        console.log(`Success`);
+    } else {
+        console.log(`Errors (x${errorCount}), skipped`);
+        writeTsconfigSync(tsconfigPath, originalConfig);
+    }
+
+    return success;
+}
+
+const buildCompletePattern = /Found (\d+) errors?\. Watching for file changes\./gi;
+async function waitForBuildComplete(tscWatchProcess) {
+    const match = await waitForStdoutMatching(tscWatchProcess, buildCompletePattern);
+    const errorCount = +match[1];
+    return errorCount;
+}
+
+async function waitForStdoutMatching(child, pattern) {
+    return new Promise(resolve => {
         const listener = data => {
             const textOut = data.toString();
-            const match = buildCompletePattern.exec(textOut);
+            const match = pattern.exec(textOut);
             if (match) {
-                const errorCount = +match[1];
-                if (errorCount === 0) {
-                    console.log(`Success`);
-                } else {
-                    console.log(`Errors (x${errorCount}), skipped`);
-                    writeTsconfigSync(tsconfigPath, originalConfig);
-                }
-
                 child.stdout.removeListener('data', listener);
-                resolve();
+                resolve(match);
             }
         };
         child.stdout.on('data', listener);
-
-        writeTsconfigSync(tsconfigPath, newConfig);
     });
 }
+
+main().catch(error => {
+    console.error(error.stack);
+    process.exit(1);
+});

tools/strict-null-checks/eligible-file-finder.js

@@ -2,8 +2,9 @@
 // Licensed under the MIT License.
 
 // @ts-check
+const fs = require('fs');
 const path = require('path');
-const { getImportsForFile } = require('./import-finder');
+const { getMemoizedImportsForFile } = require('./import-finder');
 const glob = require('glob');
 const config = require('./config');
 
@@ -34,16 +35,6 @@ const getAllTsFiles = (srcRoot, options) => {
  * @param {{ includeTests: boolean }} [options]
  */
 async function getUncheckedLeafFiles(repoRoot, options) {
-    const imports = new Map();
-    const getMemoizedImportsForFile = (file, srcRoot) => {
-        if (imports.has(file)) {
-            return imports.get(file);
-        }
-        const importList = getImportsForFile(file, srcRoot);
-        imports.set(file, importList);
-        return importList;
-    };
-
     const srcRoot = path.join(repoRoot, 'src');
 
     const checkedFiles = await getCheckedFiles(repoRoot);
@@ -63,7 +54,8 @@ async function getUncheckedLeafFiles(repoRoot, options) {
 }
 
 async function getCheckedFiles(tsconfigDir) {
-    const tsconfigContent = require(path.join(tsconfigDir, config.targetTsconfig));
+    const tsconfigPath = path.join(tsconfigDir, config.targetTsconfig);
+    const tsconfigContent = JSON.parse(fs.readFileSync(tsconfigPath).toString());
 
     const set = new Set(
         tsconfigContent.files.map(f => path.join(tsconfigDir, f).replace(/\\/g, '/')),

tools/strict-null-checks/import-finder.js

@@ -6,7 +6,17 @@ const path = require('path');
 const ts = require('typescript');
 const fs = require('fs');
 
-module.exports.getImportsForFile = function getImportsForFile(parentFilePath, srcRoot) {
+const imports = new Map();
+const getMemoizedImportsForFile = (file, srcRoot) => {
+    if (imports.has(file)) {
+        return imports.get(file);
+    }
+    const importList = getImportsForFile(file, srcRoot);
+    imports.set(file, importList);
+    return importList;
+};
+
+function getImportsForFile(parentFilePath, srcRoot) {
     const fileInfo = ts.preProcessFile(fs.readFileSync(parentFilePath).toString());
     return fileInfo.importedFiles
         .map(importedFile => importedFile.fileName)
@@ -43,4 +53,9 @@ module.exports.getImportsForFile = function getImportsForFile(parentFilePath, sr
             }
             return filePath;
         });
+}
+
+module.exports = {
+    getImportsForFile,
+    getMemoizedImportsForFile,
 };