facebook
diff --git a/‎404.html
+26 b/‎404.html
+26
diff --git a/‎CNAME
+1 b/‎CNAME
+1
diff --git a/‎_src/cli/annotate-exports.md
+80 b/‎_src/cli/annotate-exports.md
+80
diff --git a/‎_src/cli/coverage.md
+128 b/‎_src/cli/coverage.md
+128
@@ -0,0 +1,26 @@
+<!doctype html>
+<html lang="en" dir="ltr" class="plugin-native plugin-id-default">
+<head>
+<meta charset="UTF-8">
+<meta name="generator" content="Docusaurus v2.4.1">
+<title data-rh="true">Page Not Found | Flow</title><meta data-rh="true" name="viewport" content="width=device-width,initial-scale=1"><meta data-rh="true" name="twitter:card" content="summary_large_image"><meta data-rh="true" property="og:url" content="https://flow.org/404.html"><meta data-rh="true" name="docusaurus_locale" content="en"><meta data-rh="true" name="docusaurus_tag" content="default"><meta data-rh="true" name="docsearch:language" content="en"><meta data-rh="true" name="docsearch:docusaurus_tag" content="default"><meta data-rh="true" property="og:title" content="Page Not Found | Flow"><link data-rh="true" rel="icon" href="/img/favicon.png"><link data-rh="true" rel="canonical" href="https://flow.org/404.html"><link data-rh="true" rel="alternate" href="https://flow.org/404.html" hreflang="en"><link data-rh="true" rel="alternate" href="https://flow.org/404.html" hreflang="x-default"><link data-rh="true" rel="preconnect" href="https://P6T3E8XPGT-dsn.algolia.net" crossorigin="anonymous"><link rel="alternate" type="application/rss+xml" href="/blog/rss.xml" title="Flow RSS Feed">
+<link rel="alternate" type="application/atom+xml" href="/blog/atom.xml" title="Flow Atom Feed">
+
+<link rel="preconnect" href="https://www.google-analytics.com">
+<script>window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)},ga.l=+new Date,ga("create","UA-49208336-4","auto"),ga("set","anonymizeIp",!0),ga("send","pageview")</script>
+<script async src="https://www.google-analytics.com/analytics.js"></script>
+
+
+<link rel="search" type="application/opensearchdescription+xml" title="Flow" href="/opensearch.xml"><link rel="stylesheet" href="/assets/css/styles.aa18815f.css">
+<link rel="preload" href="/assets/js/runtime~main.b1727f31.js" as="script">
+<link rel="preload" href="/assets/js/main.77ecfc36.js" as="script">
+</head>
+<body class="navigation-with-keyboard">
+<script>!function(){function t(t){document.documentElement.setAttribute("data-theme",t)}var e=function(){var t=null;try{t=new URLSearchParams(window.location.search).get("docusaurus-theme")}catch(t){}return t}()||function(){var t=null;try{t=localStorage.getItem("theme")}catch(t){}return t}();t(null!==e?e:"light")}()</script>
+
+<div style="display: none; text-align: center; background-color: white; color: black;" id="internaldocs-banner"></div><div id="__docusaurus">
+<div role="region" aria-label="Skip to main content"><a class="skipToContent_fXgn" href="#__docusaurus_skipToContent_fallback">Skip to main content</a></div><nav aria-label="Main" class="navbar navbar--fixed-top"><div class="navbar__inner"><div class="navbar__items"><button aria-label="Toggle navigation bar" aria-expanded="false" class="navbar__toggle clean-btn" type="button"><svg width="30" height="30" viewBox="0 0 30 30" aria-hidden="true"><path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path></svg></button><a class="navbar__brand" href="/"><div class="navbar__logo"><img src="/img/logo.svg" alt="My Facebook Project Logo" class="themedImage_ToTc themedImage--light_HNdA"><img src="/img/logo.svg" alt="My Facebook Project Logo" class="themedImage_ToTc themedImage--dark_i4oU"></div></a><a class="navbar__item navbar__link" href="/en/docs/getting-started/">Getting Started</a><a class="navbar__item navbar__link" href="/en/docs/">Docs</a><a class="navbar__item navbar__link" href="/try/">Try</a><a class="navbar__item navbar__link" href="/blog/">Blog</a></div><div class="navbar__items navbar__items--right"><a href="https://twitter.com/flowtype" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar__icon twitter__link" aria-label="Twitter"></a><a href="http://stackoverflow.com/questions/tagged/flowtype" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar__icon stackoverflow__link" aria-label="Stack Overflow"></a><a href="https://github.com/facebook/flow" target="_blank" rel="noopener noreferrer" class="navbar__item navbar__link navbar__icon github__link" aria-label="GitHub"></a><div class="searchBox_ZlJk"><button type="button" class="DocSearch DocSearch-Button" aria-label="Search"><span class="DocSearch-Button-Container"><svg width="20" height="20" class="DocSearch-Search-Icon" viewBox="0 0 20 20"><path d="M14.386 14.386l4.0877 4.0877-4.0877-4.0877c-2.9418 2.9419-7.7115 2.9419-10.6533 0-2.9419-2.9418-2.9419-7.7115 0-10.6533 2.9418-2.9419 7.7115-2.9419 10.6533 0 2.9419 2.9418 2.9419 7.7115 0 10.6533z" stroke="currentColor" fill="none" fill-rule="evenodd" stroke-linecap="round" stroke-linejoin="round"></path></svg><span class="DocSearch-Button-Placeholder">Search</span></span><span class="DocSearch-Button-Keys"></span></button></div></div></div><div role="presentation" class="navbar-sidebar__backdrop"></div></nav><div id="__docusaurus_skipToContent_fallback" class="main-wrapper mainWrapper_z2l0"><main class="container margin-vert--xl"><div class="row"><div class="col col--6 col--offset-3"><h1 class="hero__title">Page Not Found</h1><p>We could not find what you were looking for.</p><p>Please contact the owner of the site that linked you to the original URL and let them know their link is broken.</p></div></div></main></div><footer class="footer footer--dark"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title">Learn</div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/en/docs/getting-started/">Getting Started</a></li></ul></div><div class="col footer__col"><div class="footer__title">Community</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://twitter.com/flowtype" target="_blank" rel="noopener noreferrer" class="footer__link-item">Twitter<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://discordapp.com/invite/8ezwRUK" target="_blank" rel="noopener noreferrer" class="footer__link-item">Discord<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div><div class="col footer__col"><div class="footer__title">More</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://medium.com/flow-type" target="_blank" rel="noopener noreferrer" class="footer__link-item">Medium</a></li><li class="footer__item"><a href="https://github.com/facebook/flow" target="_blank" rel="noopener noreferrer" class="footer__link-item">GitHub<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div><div class="col footer__col"><div class="footer__title">Legal</div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://opensource.facebook.com/legal/privacy/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Privacy<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/terms/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Terms<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/data-policy/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Data Policy<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://opensource.facebook.com/legal/cookie-policy/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Cookie Policy<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div></div><div class="footer__bottom text--center"><div class="margin-bottom--sm"><a href="https://opensource.facebook.com" rel="noopener noreferrer" class="footerLogoLink_BH7S"><img src="/img/oss_logo.png" alt="Facebook Open Source Logo" class="themedImage_ToTc themedImage--light_HNdA footer__logo"><img src="/img/oss_logo.png" alt="Facebook Open Source Logo" class="themedImage_ToTc themedImage--dark_i4oU footer__logo"></a></div><div class="footer__copyright">Copyright © 2025 Meta Platforms, Inc. Built with Docusaurus.</div></div></div></footer></div>
+<script src="/assets/js/runtime~main.b1727f31.js"></script>
+<script src="/assets/js/main.77ecfc36.js"></script>
+</body>
+</html>
@@ -0,0 +1 @@
+flow.org
@@ -0,0 +1,80 @@
+---
+title: Flow Annotate-Exports
+slug: /cli/annotate-exports
+---
+
+Upgrading to [Types-First](../../lang/types-first) mode may require a substantial
+number of type annotations at module boundaries. To help with the process of
+upgrading large codebases, we are providing a codemod command, whose goal is to
+fill in these missing annotations. This command is included in the Flow binary
+in versions `>= 0.125`.
+
+> Note: As of version 0.134, types-first is the default mode. If you are using a
+version `>=0.134`, make sure you set `types_first=false` in your .flowconfig while
+running this codemod.
+
+This command uses types that Flow infers, to fill in positions that would otherwise
+raise *signature-verification* failures. It will include the necessary type import
+statements, as long as the respective types are exported from their defining modules.
+
+It is designed for use on multiple files at once, rather than one file at a time.
+For this reason it doesn't connect to an existing Flow server, but rather starts
+a checking process of its own.
+
+As is typical with such mechanized approaches, it comes with a few caveats:
+
+1. It won’t be able to fill in every required type annotation. Some cases will
+require manual effort.
+2. Inserted annotations may cause new flow errors, since it’s not always possible
+to match inferred type with types that can be written as annotations.
+3. File formatting may be affected. If a code formatter (e.g. prettier) is used,
+it is recommended that you run it after the codemod has finished running.
+
+
+### How to apply the codemod {#toc-how-to-apply-the-codemod}
+
+A typical way to invoke this command is
+
+```
+flow codemod annotate-exports \
+  --write \
+  --repeat \
+  --log-level info \
+  /path/to/folder \
+  2> out.log
+```
+
+This command will transform files under `/path/to/folder`. This does not need to
+be the root directory (the one containing `.flowconfig`).
+
+It uses the following flags:
+* `--write` will update files that require annotations under `/path/to/folder`
+in-place. Without this flag the resulting files will be printed on the command line.
+
+* `--repeat` ensures that the transformation will be applied until no more files
+change. This mode is necessary here, because each new type the codemod adds may
+require new locations to be annotated.
+
+* `--log-level info` outputs useful debugging information in the standard error stream.
+This option might lead to verbose output, so we're redirecting the error output
+to a log file `out.log`.
+
+Another convenient way to provide the input is by passing the flag
+```
+--input-file file.txt
+```
+where `file.txt` contains a specific list of files to be transformed.
+
+### Codemod output {#toc-codemod-output}
+
+After each iteration of the codemod, a summary will be printed on the CLI. This
+summary includes statistical information about the number of annotations that were
+added, and how many locations were skipped. It also prints counts for various kinds
+of errors that were encountered. These can be matched to the errors printed in the
+logs.
+
+A common error case is when a type `A`, defined in a file `a.js`, but not exported,
+is inferred in file `b.js`. The codemod will skip adding this annotation and report
+an error in the logs. The fix this case, you can export `A` in `a.js`. Note that
+it is not necessary to manually import `A` in `b.js`. The codemod will do this
+automatically.
@@ -0,0 +1,128 @@
+---
+title: Flow Coverage
+slug: /cli/coverage
+---
+The coverage command provides a metric of the amount of checking that Flow has
+performed on each part of your code. A program with high Flow coverage should
+increase your confidence that Flow has detected any potential runtime errors.
+
+The determining factor for this is the presence of [`any`](../../types/any/) in the
+inferred type of each expression. An expression whose inferred type is `any` is
+considered *uncovered*, otherwise it is considered *covered*.
+
+To see why this metric was chosen for determining Flow's effectiveness, consider
+the example
+
+```js flow-check
+const one: any = 1;
+one();
+```
+
+This code leads to a runtime type error, since we are attempting to perform a call
+on a number. Flow, however, does not flag an error here, because we have annotated
+variable `one` as `any`. Flow's checking is effectively turned off whenever `any`
+is involved, so it will silently allow the call. The use of this *unsafe* type has
+rendered the type checker ineffective, and the coverage metric is here to surface
+this, by reporting all instances of `one` as uncovered.
+
+## Design Space {#toc-design-space}
+
+**Which types should be "covered"?**
+
+What was described above is a rather coarse grained way to determine coverage. One
+could imagine a criterion that flags expressions as uncovered if *any* part of their
+type includes `any`, for example `Array<any>`. While there is value in a metric like
+this, the "uncovered" part of the type will typically be uncovered through various
+operations on values of this type. For example, in the code
+
+```js flow-check
+declare const arr: Array<any>;
+arr.forEach(x => {});
+```
+
+the parameter `x` will be flagged as uncovered. Also, in practice, a strict criterion
+like this would be too noisy and rather expensive to compute on the fly.
+
+**Union types**
+
+An exception to this principle are union types: the type `number | any` is considered
+*uncovered*, even though technically `any` is not the top-level constructor.
+Unions merely encode an option among *a set of* other types. In that sense we are
+conservatively viewing an expression as uncovered, when at least one possible type
+of that expression causes limited checking. For example, in the code
+
+```js flow-check
+let x: number | any = 1;
+x = "a";
+```
+
+Flow will let you assign anything to `x`, which reduces confidence in the use
+of `x` as a number. Thus `x` is considered uncovered.
+
+**The empty type**
+
+An interesting type from a coverage perspective is the [`empty`](../../types/empty) type.
+This type roughly corresponds to *dead code*. As such checking around expressions with
+type `empty` is more relaxed, but for a good reason: this code will not be executed at
+runtime. Since it is a common practice to clean up such code, Flow coverage will
+also report code whose type is inferred to be `empty`, but distinguishes it from
+the case of `any`.
+
+
+## Command Line Use {#toc-command-line-use}
+
+To find out the coverage of a file foo.js with the following contents
+
+```js flow-check
+function add(one: any, two: any): number {
+  return one + two;
+}
+
+add(1, 2);
+```
+
+you can issue the following command
+
+```
+$ flow coverage file.js
+Covered: 50.00% (5 of 10 expressions)
+```
+This output means that 5 out of the 10 nodes of this program were inferred to have type
+`any`. To see exactly which parts are uncovered you can also pass one of the following
+flags:
+* `--color`: This will print foo.js on the terminal with the uncovered locations in
+red color. E.g. `flow coverage --color file.js`
+* `--json`: This will list out all location spans that are uncovered under
+the tag `"uncovered_locs"`. E.g. `flow coverage --json file.js`
+
+Finally, as an example of dead code, consider the code:
+
+```js flow-check
+function f(x: 'a' | 'b') {
+  if (x === 'a') {
+    // ...
+  } else if (x === 'b') {
+    // ...
+  } else {
+    x;
+  }
+}
+```
+
+The final `else` clause should never be reached, as we've already checked for both members of the union.
+Because of this, `x` is inferred to have the type `empty` in that branch.
+
+In the colored version of this command, these parts appear in blue color,
+and in the JSON version they are under the field `"empty_locs"`.
+
+**Use on multiple files**
+
+If you want to check coverage of multiple files at once, Flow offers the
+`batch-coverage` command:
+```
+$ flow batch-coverage dir/
+```
+will report coverage statistics for each file under `dir/`, as well as aggregate
+results.
+
+Note that `batch-coverage` requires a non-lazy Flow server.