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jergasonclaude
jergason
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inject CSS and script into body when head tag is missing (#6)
pages like old.reddit.com start with <body> and have no <head> tag. our HeadInjector only fired on <head>, so these pages got no CSS text-transform, no uppercase script, no fetch/XHR patching — nothing. replaces HeadInjector with ScriptAndStyleInjector that registers on both head and body. uses an injected flag to prevent double injection. appends to head (normal), prepends to body (fallback). Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>
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Lines changed: 26 additions & 10 deletions

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‎src/rewriter.test.ts‎

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Original file line numberDiff line numberDiff line change
@@ -108,6 +108,19 @@ describe("HTMLRewriter integration", () => {
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expect(resp.headers.get("access-control-allow-origin")).toBe("*");
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});
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it("does not double-inject CSS when both head and body exist", async () => {
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const resp = await worker.fetch("/browse/https://httpbin.org/html");
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if (resp.status !== 200) return;
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const html = await resp.text();
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const cssCount = (html.match(/text-transform: uppercase/g) || []).length;
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expect(cssCount).toBe(1);
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const scriptCount = (html.match(/walkAndUppercase/g) || []).length;
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// walkAndUppercase appears multiple times within the single script (definition + calls)
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// but should NOT appear in a second duplicate script block
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expect(scriptCount).toBeGreaterThan(0);
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expect(scriptCount).toBeLessThan(10);
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});
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it("injects resolveForProxy for relative URL handling", async () => {
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const resp = await worker.fetch("/browse/https://httpbin.org/html");
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if (resp.status !== 200) return;

‎src/rewriter.ts‎

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Original file line numberDiff line numberDiff line change
@@ -81,17 +81,18 @@ class SrcsetRewriter implements HTMLRewriterElementContentHandlers {
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}
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}
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class HeadInjector implements HTMLRewriterElementContentHandlers {
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constructor(private targetUrl: string) {}
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const INJECTED_CSS = `<style>*:not(input):not(textarea):not(select):not(code):not(pre):not(script):not(style) { text-transform: uppercase !important; } code, pre, textarea, svg { text-transform: none !important; }</style>`;
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class ScriptAndStyleInjector implements HTMLRewriterElementContentHandlers {
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injected = false;
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element(el: Element) {
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// no <base> tag — it would redirect /browse/... paths to the target origin
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// URLRewriter already resolves all relative URLs to absolute proxy paths
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el.append(
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`<style>*:not(input):not(textarea):not(select):not(code):not(pre):not(script):not(style) { text-transform: uppercase !important; } code, pre, textarea, svg { text-transform: none !important; }</style>`,
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{ html: true },
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);
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el.append(`<script>${uppercaseScript}</script>`, { html: true });
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if (this.injected) return;
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this.injected = true;
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// prepend into body (fallback for pages without <head>), append into head
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const method = el.tagName === "head" ? "append" : "prepend";
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el[method](INJECTED_CSS, { html: true });
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el[method](`<script>${uppercaseScript}</script>`, { html: true });
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}
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}
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@@ -106,8 +107,10 @@ class MetaCSPRemover implements HTMLRewriterElementContentHandlers {
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export function buildRewriter(targetUrl: string): HTMLRewriter {
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const uppercaser = new TextUppercaser();
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const injector = new ScriptAndStyleInjector();
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return new HTMLRewriter()
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.on("head", new HeadInjector(targetUrl))
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.on("head", injector)
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.on("body", injector)
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.on("meta", new MetaCSPRemover())
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.on("a, area", new URLRewriter(targetUrl, "href"))
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.on("img", new URLRewriter(targetUrl, "src"))

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