<!DOCTYPE HTML>
<html lang="en" class="navy sidebar-visible" dir="ltr">
<head>
<meta charset="UTF-8">
<title>Scanner - towl Documentation</title>
<meta name="description" content="Documentation for towl - a fast CLI tool to scan codebases for TODO comments">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff">
<link rel="icon" href="../favicon.svg">
<link rel="shortcut icon" href="../favicon.png">
<link rel="stylesheet" href="../css/variables.css">
<link rel="stylesheet" href="../css/general.css">
<link rel="stylesheet" href="../css/chrome.css">
<link rel="stylesheet" href="../css/print.css" media="print">
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
<link rel="stylesheet" href="../fonts/fonts.css">
<link rel="stylesheet" id="highlight-css" href="../highlight.css">
<link rel="stylesheet" id="tomorrow-night-css" href="../tomorrow-night.css">
<link rel="stylesheet" id="ayu-highlight-css" href="../ayu-highlight.css">
<script>
const path_to_root = "../";
const default_light_theme = "navy";
const default_dark_theme = "navy";
window.path_to_searchindex_js = "../searchindex.js";
</script>
<script src="../toc.js"></script>
</head>
<body>
<div id="mdbook-help-container">
<div id="mdbook-help-popup">
<h2 class="mdbook-help-title">Keyboard shortcuts</h2>
<div>
<p>Press <kbd>←</kbd> or <kbd>→</kbd> to navigate between chapters</p>
<p>Press <kbd>S</kbd> or <kbd>/</kbd> to search in the book</p>
<p>Press <kbd>?</kbd> to show this help</p>
<p>Press <kbd>Esc</kbd> to hide this help</p>
</div>
</div>
</div>
<div id="body-container">
<script>
try {
let theme = localStorage.getItem('mdbook-theme');
let sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<script>
const default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? default_dark_theme : default_light_theme;
let theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
const html = document.documentElement;
html.classList.remove('navy')
html.classList.add(theme);
html.classList.add("js");
</script>
<input type="checkbox" id="sidebar-toggle-anchor" class="hidden">
<script>
let sidebar = null;
const sidebar_toggle = document.getElementById("sidebar-toggle-anchor");
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
} else {
sidebar = 'hidden';
sidebar_toggle.checked = false;
}
if (sidebar === 'visible') {
sidebar_toggle.checked = true;
} else {
html.classList.remove('sidebar-visible');
}
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<mdbook-sidebar-scrollbox class="sidebar-scrollbox"></mdbook-sidebar-scrollbox>
<noscript>
<iframe class="sidebar-iframe-outer" src="../toc.html"></iframe>
</noscript>
<div id="sidebar-resize-handle" class="sidebar-resize-handle">
<div class="sidebar-resize-indicator"></div>
</div>
</nav>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar-hover-placeholder"></div>
<div id="menu-bar" class="menu-bar sticky">
<div class="left-buttons">
<label id="sidebar-toggle" class="icon-button" for="sidebar-toggle-anchor" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</label>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="default_theme">Auto</button></li>
<li role="none"><button role="menuitem" class="theme" id="light">Light</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search (`/`)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="/ s" aria-controls="searchbar">
<i class="fa fa-search"></i>
</button>
</div>
<h1 class="menu-title">towl Documentation</h1>
<div class="right-buttons">
<a href="../print.html" title="Print this book" aria-label="Print this book">
<i id="print-button" class="fa fa-print"></i>
</a>
<a href="https://github.com/glottologist/towl" title="Git repository" aria-label="Git repository">
<i id="git-repository-button" class="fa fa-github"></i>
</a>
<a href="https://github.com/glottologist/towl/edit/main/docs/src/src/api/scanner.md" title="Suggest an edit" aria-label="Suggest an edit" rel="edit">
<i id="git-edit-button" class="fa fa-edit"></i>
</a>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<div class="search-wrapper">
<input type="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
<div class="spinner-wrapper">
<i class="fa fa-spinner fa-spin"></i>
</div>
</div>
</form>
<div id="searchresults-outer" class="searchresults-outer hidden">
<div id="searchresults-header" class="searchresults-header"></div>
<ul id="searchresults">
</ul>
</div>
</div>
<script>
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<main>
<h1 id="scanner"><a class="header" href="#scanner">Scanner</a></h1>
<p>The scanner walks a directory tree, filters files by extension and exclude patterns, reads content, and delegates to the parser for TODO extraction.</p>
<h2 id="scanner-1"><a class="header" href="#scanner-1"><code>Scanner</code></a></h2>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct Scanner {
parser: Parser,
config: ParsingConfig,
}
<span class="boring">}</span></code></pre></pre>
<h3 id="constructor"><a class="header" href="#constructor">Constructor</a></h3>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub fn new(config: ParsingConfig) -> Result<Self, TowlScannerError>
<span class="boring">}</span></code></pre></pre>
<p>Creates a new scanner. Compiles all regex patterns from the config during construction so pattern errors are caught early.</p>
<h3 id="scan"><a class="header" href="#scan"><code>scan</code></a></h3>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub async fn scan(&self, path: PathBuf) -> Result<ScanResult, TowlScannerError>
<span class="boring">}</span></code></pre></pre>
<p>Recursively scans <code>path</code> for TODO comments. Returns a <code>ScanResult</code> on success.</p>
<p><strong>Behaviour:</strong></p>
<ol>
<li>Validates the path (rejects path traversal)</li>
<li>Walks the directory using the <code>ignore</code> crate (respects <code>.gitignore</code>)</li>
<li>Filters files by extension (<code>file_extensions</code> config)</li>
<li>Skips files matching <code>exclude_patterns</code></li>
<li>Skips files larger than <code>MAX_FILE_SIZE</code> (10 MB)</li>
<li>Reads and parses each file asynchronously via <code>tokio::fs</code></li>
<li>Collects results until a resource limit is reached or the walk completes</li>
</ol>
<p><strong>Errors:</strong></p>
<ul>
<li><code>InvalidPath</code> -- Path contains traversal components (<code>..</code>)</li>
<li><code>FileTooLarge</code> -- File exceeds 10 MB</li>
<li><code>TooManyTodos</code> -- Single file exceeds 10,000 TODOs</li>
<li><code>TooManyFiles</code> -- Walk exceeds 100,000 files</li>
<li><code>UnableToReadFileAtPath</code> -- I/O error reading a specific file</li>
<li><code>UnableToWalkFile</code> -- Directory walk error</li>
<li><code>ParsingError</code> -- Regex or parsing failure (propagated from parser)</li>
</ul>
<h2 id="scanresult"><a class="header" href="#scanresult"><code>ScanResult</code></a></h2>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub struct ScanResult {
pub todos: Vec<TodoComment>,
pub files_scanned: usize,
pub files_skipped: usize,
pub files_errored: usize,
pub duration: std::time::Duration,
}
<span class="boring">}</span></code></pre></pre>
<h3 id="methods"><a class="header" href="#methods">Methods</a></h3>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub const fn all_files_failed(&self) -> bool
<span class="boring">}</span></code></pre></pre>
<p>Returns <code>true</code> when <code>files_scanned == 0</code> and <code>files_errored > 0</code>. Indicates a likely permissions or path issue where no files could be read.</p>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>pub const fn is_clean(&self) -> bool
<span class="boring">}</span></code></pre></pre>
<p>Returns <code>true</code> when <code>todos</code> is empty and <code>files_errored == 0</code>. A clean scan with no issues.</p>
<h2 id="resource-limits"><a class="header" href="#resource-limits">Resource Limits</a></h2>
<div class="table-wrapper"><table><thead><tr><th>Constant</th><th>Value</th><th>Trigger</th></tr></thead><tbody>
<tr><td><code>MAX_FILE_SIZE</code></td><td>10,485,760 bytes (10 MB)</td><td>File skipped</td></tr>
<tr><td><code>MAX_TODO_COUNT</code></td><td>10,000</td><td>Error for that file</td></tr>
<tr><td><code>MAX_TOTAL_TODO_COUNT</code></td><td>100,000</td><td>Scan stops, returns partial</td></tr>
<tr><td><code>MAX_FILES_SCANNED</code></td><td>100,000</td><td>Scan stops, returns partial</td></tr>
</tbody></table>
</div>
<h2 id="example"><a class="header" href="#example">Example</a></h2>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use towl::config::ParsingConfig;
use towl::scanner::Scanner;
use std::path::PathBuf;
let config = ParsingConfig::default();
let scanner = Scanner::new(config)?;
let result = scanner.scan(PathBuf::from(".")).await?;
println!("Found {} TODOs in {} files", result.todos.len(), result.files_scanned);
if result.all_files_failed() {
eprintln!("Warning: no files could be read");
}
<span class="boring">}</span></code></pre></pre>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<a rel="prev" href="../api/overview.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next prefetch" href="../api/parser.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
<a rel="prev" href="../api/overview.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next prefetch" href="../api/parser.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
</nav>
</div>
<script>
window.playground_copyable = true;
</script>
<script src="../elasticlunr.min.js"></script>
<script src="../mark.min.js"></script>
<script src="../searcher.js"></script>
<script src="../clipboard.min.js"></script>
<script src="../highlight.js"></script>
<script src="../book.js"></script>
</div>
</body>
</html>