Extract pure native request header helpers

src/modules/services/ObsidianAPIService.ts

@@ -6,6 +6,7 @@ import { ObsidianConfirm } from "./ObsidianConfirm";
 import type { Confirm } from "@vrtmrz/livesync-commonlib/compat/interfaces/Confirm";
 import { requestUrl, type RequestUrlParam } from "@/deps";
 import { compatGlobal } from "@vrtmrz/livesync-commonlib/compat/common/coreEnvFunctions";
+import { createNativeRequestHeaders } from "./nativeRequestHeaders";
 // All Services will be migrated to be based on Plain Services, not Injectable Services.
 // This is a migration step.
 
@@ -16,43 +17,6 @@ declare module "obsidian" {
     }
 }
 
-const cacheReuseDirectives = new Set(["max-age", "max-stale", "min-fresh", "only-if-cached"]);
-
-function splitHeaderDirectives(value: string): string[] {
-    const directives: string[] = [];
-    let start = 0;
-    let inQuotes = false;
-    let escaped = false;
-
-    for (let index = 0; index < value.length; index++) {
-        const character = value[index];
-        if (inQuotes && escaped) {
-            escaped = false;
-            continue;
-        }
-        if (inQuotes && character === "\\") {
-            escaped = true;
-            continue;
-        }
-        if (character === '"') {
-            inQuotes = !inQuotes;
-        } else if (character === "," && !inQuotes) {
-            const directive = value.slice(start, index).trim();
-            if (directive) directives.push(directive);
-            start = index + 1;
-        }
-    }
-
-    const lastDirective = value.slice(start).trim();
-    if (lastDirective) directives.push(lastDirective);
-    return directives;
-}
-
-function getDirectiveName(directive: string): string {
-    const equalsIndex = directive.indexOf("=");
-    return (equalsIndex === -1 ? directive : directive.slice(0, equalsIndex)).trim().toLowerCase();
-}
-
 export class ObsidianAPIService extends InjectableAPIService<ObsidianServiceContext> {
     _customHandler: ObsHttpHandler | undefined;
     _confirmInstance: Confirm;
@@ -212,46 +176,8 @@ export class ObsidianAPIService extends InjectableAPIService<ObsidianServiceCont
                 }
             }
         }
-        const transformedHeaders = { ...optHeaders };
-        // Delete headers that should not be sent by native fetch,
-        // they are controlled by the browser and may cause CORS preflight failure if sent manually.
-        delete transformedHeaders["host"];
-        delete transformedHeaders["Host"];
-        delete transformedHeaders["content-length"];
-        delete transformedHeaders["Content-Length"];
         const cacheMode = opts?.cache ?? (req instanceof Request ? req.cache : undefined);
-        if (["no-cache", "no-store"].includes(cacheMode ?? "") && ["GET", "HEAD"].includes(method.toUpperCase())) {
-            // requestUrl has no cache option; no-store alone can reuse an existing cached response.
-            const enforceNoStore = cacheMode === "no-store";
-            const cacheControlKeys = Object.keys(transformedHeaders).filter(
-                (key) => key.toLowerCase() === "cache-control"
-            );
-            const cacheControlDirectives = cacheControlKeys
-                .flatMap((key) => splitHeaderDirectives(transformedHeaders[key]))
-                .filter((directive) => {
-                    const name = getDirectiveName(directive);
-                    return (
-                        !cacheReuseDirectives.has(name) &&
-                        name !== "no-cache" &&
-                        (!enforceNoStore || name !== "no-store")
-                    );
-                });
-            const cacheControlKey = cacheControlKeys[0] ?? "cache-control";
-            for (const key of cacheControlKeys) delete transformedHeaders[key];
-            transformedHeaders[cacheControlKey] = [
-                ...cacheControlDirectives,
-                "no-cache",
-                ...(enforceNoStore ? ["no-store"] : []),
-            ].join(", ");
-
-            const pragmaKeys = Object.keys(transformedHeaders).filter((key) => key.toLowerCase() === "pragma");
-            const pragmaDirectives = pragmaKeys
-                .flatMap((key) => splitHeaderDirectives(transformedHeaders[key]))
-                .filter((directive) => getDirectiveName(directive) !== "no-cache");
-            const pragmaKey = pragmaKeys[0] ?? "pragma";
-            for (const key of pragmaKeys) delete transformedHeaders[key];
-            transformedHeaders[pragmaKey] = [...pragmaDirectives, "no-cache"].join(", ");
-        }
+        const transformedHeaders = createNativeRequestHeaders(optHeaders, method, cacheMode);
         const contentType =
             transformedHeaders["content-type"] ?? transformedHeaders["Content-Type"] ?? "application/json";
         const requestParam: RequestUrlParam = {

src/modules/services/nativeRequestHeaders.ts

@@ -0,0 +1,100 @@
+const cacheReuseDirectives = new Set(["max-age", "max-stale", "min-fresh", "only-if-cached"]);
+
+function splitHeaderDirectives(value: string): string[] {
+    const directives: string[] = [];
+    let start = 0;
+    let inQuotes = false;
+    let escaped = false;
+
+    for (let index = 0; index < value.length; index++) {
+        const character = value[index];
+        if (inQuotes && escaped) {
+            escaped = false;
+            continue;
+        }
+        if (inQuotes && character === "\\") {
+            escaped = true;
+            continue;
+        }
+        if (character === '"') {
+            inQuotes = !inQuotes;
+        } else if (character === "," && !inQuotes) {
+            const directive = value.slice(start, index).trim();
+            if (directive) directives.push(directive);
+            start = index + 1;
+        }
+    }
+
+    const lastDirective = value.slice(start).trim();
+    if (lastDirective) directives.push(lastDirective);
+    return directives;
+}
+
+function getDirectiveName(directive: string): string {
+    const equalsIndex = directive.indexOf("=");
+    return (equalsIndex === -1 ? directive : directive.slice(0, equalsIndex)).trim().toLowerCase();
+}
+
+/**
+ * Whether native GET or HEAD requests must revalidate an explicitly bypassed cache.
+ *
+ * @param method - HTTP method, compared without regard to letter case.
+ * @param cacheMode - Effective Request or options cache mode.
+ * @returns True only for GET/HEAD with `no-cache` or `no-store`.
+ */
+export function shouldRevalidateNativeRequest(method: string, cacheMode: RequestCache | undefined): boolean {
+    return (cacheMode === "no-cache" || cacheMode === "no-store") && ["GET", "HEAD"].includes(method.toUpperCase());
+}
+
+function shouldRetainCacheControlDirective(directive: string, enforceNoStore: boolean): boolean {
+    const name = getDirectiveName(directive);
+    return !cacheReuseDirectives.has(name) && name !== "no-cache" && (!enforceNoStore || name !== "no-store");
+}
+
+/**
+ * Copy request headers and apply the native fetch adapter's header/cache policy.
+ *
+ * @param headers - Merged input headers; this function does not mutate them.
+ * @param method - HTTP method used to decide whether cache revalidation applies.
+ * @param cacheMode - Effective Request or options cache mode.
+ * @returns Fresh headers with the adapter's native-controlled headers removed.
+ * Revalidated GET/HEAD requests retain non-conflicting directives and receive
+ * `no-cache`; `no-store` also adds that directive. Existing header spelling is retained.
+ */
+export function createNativeRequestHeaders(
+    headers: Readonly<Record<string, string>>,
+    method: string,
+    cacheMode: RequestCache | undefined
+): Record<string, string> {
+    const transformedHeaders = { ...headers };
+    // Delete headers that should not be sent by native fetch,
+    // they are controlled by the browser and may cause CORS preflight failure if sent manually.
+    delete transformedHeaders["host"];
+    delete transformedHeaders["Host"];
+    delete transformedHeaders["content-length"];
+    delete transformedHeaders["Content-Length"];
+    if (shouldRevalidateNativeRequest(method, cacheMode)) {
+        // requestUrl has no cache option; no-store alone can reuse an existing cached response.
+        const enforceNoStore = cacheMode === "no-store";
+        const cacheControlKeys = Object.keys(transformedHeaders).filter((key) => key.toLowerCase() === "cache-control");
+        const cacheControlDirectives = cacheControlKeys
+            .flatMap((key) => splitHeaderDirectives(transformedHeaders[key]))
+            .filter((directive) => shouldRetainCacheControlDirective(directive, enforceNoStore));
+        const cacheControlKey = cacheControlKeys[0] ?? "cache-control";
+        for (const key of cacheControlKeys) delete transformedHeaders[key];
+        transformedHeaders[cacheControlKey] = [
+            ...cacheControlDirectives,
+            "no-cache",
+            ...(enforceNoStore ? ["no-store"] : []),
+        ].join(", ");
+
+        const pragmaKeys = Object.keys(transformedHeaders).filter((key) => key.toLowerCase() === "pragma");
+        const pragmaDirectives = pragmaKeys
+            .flatMap((key) => splitHeaderDirectives(transformedHeaders[key]))
+            .filter((directive) => getDirectiveName(directive) !== "no-cache");
+        const pragmaKey = pragmaKeys[0] ?? "pragma";
+        for (const key of pragmaKeys) delete transformedHeaders[key];
+        transformedHeaders[pragmaKey] = [...pragmaDirectives, "no-cache"].join(", ");
+    }
+    return transformedHeaders;
+}

src/modules/services/nativeRequestHeaders.unit.spec.ts

@@ -0,0 +1,84 @@
+import { describe, expect, it } from "vitest";
+import { createNativeRequestHeaders, shouldRevalidateNativeRequest } from "./nativeRequestHeaders";
+
+describe("native cache revalidation decision", () => {
+    it.each(["GET", "HEAD", "get", "head"])("revalidates explicit no-cache/no-store for %s", (method) => {
+        expect(shouldRevalidateNativeRequest(method, "no-cache")).toBe(true);
+        expect(shouldRevalidateNativeRequest(method, "no-store")).toBe(true);
+    });
+
+    it.each([undefined, "default", "reload", "force-cache", "only-if-cached"] as const)(
+        "does not strengthen cache mode %s",
+        (mode) => {
+            expect(shouldRevalidateNativeRequest("GET", mode)).toBe(false);
+            expect(shouldRevalidateNativeRequest("HEAD", mode)).toBe(false);
+        }
+    );
+
+    it.each(["POST", "PUT", "PATCH", "DELETE", "OPTIONS"])("does not revalidate %s", (method) => {
+        expect(shouldRevalidateNativeRequest(method, "no-cache")).toBe(false);
+        expect(shouldRevalidateNativeRequest(method, "no-store")).toBe(false);
+    });
+});
+
+describe("native request header creation", () => {
+    it("copies input headers and removes the existing native-controlled header forms", () => {
+        const input = Object.freeze({
+            host: "first.test",
+            Host: "second.test",
+            "content-length": "1",
+            "Content-Length": "2",
+            Authorization: "Bearer fixture",
+            "Cache-Control": "max-age=60",
+        });
+        const result = createNativeRequestHeaders(input, "GET", "default");
+        expect(result).toEqual({ Authorization: "Bearer fixture", "Cache-Control": "max-age=60" });
+        expect(result).not.toBe(input);
+        expect(input.host).toBe("first.test");
+        expect(input["Content-Length"]).toBe("2");
+    });
+
+    it.each(["GET", "HEAD"])("creates no-store revalidation headers for %s", (method) => {
+        expect(createNativeRequestHeaders({}, method, "no-store")).toEqual({
+            "cache-control": "no-cache, no-store",
+            pragma: "no-cache",
+        });
+    });
+
+    it("preserves an existing no-store directive when enforcing no-cache", () => {
+        expect(
+            createNativeRequestHeaders(
+                { "Cache-Control": "no-store, max-age=3600", Pragma: "legacy" },
+                "GET",
+                "no-cache"
+            )
+        ).toEqual({ "Cache-Control": "no-store, no-cache", Pragma: "legacy, no-cache" });
+    });
+
+    it("combines differently cased header fields and retains non-conflicting directives", () => {
+        const input = Object.freeze({
+            "Cache-Control": 'Max-Age=99, no-transform, custom="a,b", No-Cache',
+            "cache-control": "max-stale=5, min-fresh=6, only-if-cached, NO-STORE, private",
+            Pragma: 'legacy="a,b", No-Cache',
+            pragma: "extension, no-cache",
+        });
+        expect(createNativeRequestHeaders(input, "get", "no-store")).toEqual({
+            "Cache-Control": 'no-transform, custom="a,b", private, no-cache, no-store',
+            Pragma: 'legacy="a,b", extension, no-cache',
+        });
+        expect(input["cache-control"]).toContain("max-stale=5");
+    });
+
+    it("does not split directive commas inside escaped quoted strings", () => {
+        const custom = String.raw`custom="a\"b,c"`;
+        expect(createNativeRequestHeaders({ "cache-control": `${custom}, max-age=1` }, "HEAD", "no-cache")).toEqual({
+            "cache-control": `${custom}, no-cache`,
+            pragma: "no-cache",
+        });
+    });
+
+    it("retains cache headers on a non-revalidated method", () => {
+        const headers = { "cache-control": "max-age=99", Pragma: "legacy" };
+        expect(createNativeRequestHeaders(headers, "POST", "no-store")).toEqual(headers);
+    });
+});