Preserve custom headers for no-store requests

src/modules/services/ObsidianAPIService.ts

@@ -16,6 +16,43 @@ 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;
@@ -185,13 +222,26 @@ export class ObsidianAPIService extends InjectableAPIService<ObsidianServiceCont
         const cacheMode = opts?.cache ?? (req instanceof Request ? req.cache : undefined);
         if (cacheMode === "no-store" && ["GET", "HEAD"].includes(method.toUpperCase())) {
             // requestUrl has no cache option; no-store alone can reuse an existing cached response.
-            for (const key of Object.keys(transformedHeaders)) {
-                if (["cache-control", "pragma"].includes(key.toLowerCase())) {
-                    delete transformedHeaders[key];
-                }
-            }
-            transformedHeaders["cache-control"] = "no-cache, no-store";
-            transformedHeaders["pragma"] = "no-cache";
+            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" && name !== "no-store";
+                });
+            const cacheControlKey = cacheControlKeys[0] ?? "cache-control";
+            for (const key of cacheControlKeys) delete transformedHeaders[key];
+            transformedHeaders[cacheControlKey] = [...cacheControlDirectives, "no-cache", "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 contentType =
             transformedHeaders["content-type"] ?? transformedHeaders["Content-Type"] ?? "application/json";

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

@@ -94,13 +94,34 @@ describe("ObsidianAPIService.nativeFetch cache control", () => {
 
         await createService({}).nativeFetch(url, { method, cache: "no-store", headers });
 
-        expect(sentHeaders().get("cache-control")).toBe("no-cache, no-store");
-        expect(sentHeaders().get("pragma")).toBe("no-cache");
+        expect(sentHeaders().get("cache-control")).toBe("public, no-cache, no-store");
+        expect(sentHeaders().get("pragma")).toBe("cache, no-cache");
         expect(sentHeaders().get("authorization")).toBe("Basic fixture");
         expect(headers["Cache-Control"]).toBe("public, max-age=3600");
         expect(mocks.requestUrl.mock.calls[0][0]).toMatchObject({ url, method });
     });
 
+    it("preserves non-conflicting cache directives when enforcing no-store", async () => {
+        const headers = {
+            "Cache-Control": 'max-age=3600, no-transform, custom="a,b"',
+            "cAcHe-CoNtRoL": 'max-stale=30, min-fresh=5, only-if-cached, custom-two="max-age=1, only-if-cached"',
+            Pragma: 'legacy="a,b", no-cache',
+            "X-Custom-Header": "preserved",
+        };
+        const originalHeaders = { ...headers };
+
+        await createService({}).nativeFetch(url, { cache: "no-store", headers });
+
+        const sent = mocks.requestUrl.mock.calls[0][0].headers ?? {};
+        expect(sent["Cache-Control"]).toBe(
+            'no-transform, custom="a,b", custom-two="max-age=1, only-if-cached", no-cache, no-store'
+        );
+        expect(sent["cAcHe-CoNtRoL"]).toBeUndefined();
+        expect(sent.Pragma).toBe('legacy="a,b", no-cache');
+        expect(sent["X-Custom-Header"]).toBe("preserved");
+        expect(headers).toEqual(originalHeaders);
+    });
+
     it("uses the Request cache mode when the options do not override it", async () => {
         const request = new Request(url, {
             method: "HEAD",