perf: speed up build ID-finalization pipeline

packages/static/src/build/buildApp.ts

@@ -5,6 +5,7 @@ import type { ViteBuilder, MinimalPluginContextWithoutEnvironment } from "vite";
 import { rscPayloadPlaceholder, getRscPayloadPath } from "./rscPath";
 import { getModulePathFor } from "../rsc/rscModule";
 import { processRscComponents } from "./rscProcessor";
+import { replaceIdsInContent } from "./idReplacement";
 import { computeContentHash } from "./contentHash";
 import { drainStream } from "../util/drainStream";
 import { validateEntryPath, checkDuplicatePaths } from "./validateEntryPath";
@@ -91,22 +92,6 @@ function normalizeBase(base: string): string {
   return normalized === "/" ? "" : normalized;
 }
 
-/**
- * Replaces temporary IDs with final hashed IDs in content.
- */
-function replaceIdsInContent(
-  content: string,
-  idMapping: Map<string, string>,
-): string {
-  let result = content;
-  for (const [oldId, newId] of idMapping) {
-    if (oldId !== newId) {
-      result = result.replaceAll(oldId, newId);
-    }
-  }
-  return result;
-}
-
 async function buildSingleEntry(
   result: EntryBuildResult,
   idMapping: Map<string, string>,

packages/static/src/build/dependencyGraph.ts

@@ -85,9 +85,10 @@ export function topologicalSort(
   }
 
   // Nodes not in sorted result are part of cycles
+  const sortedSet = new Set(sorted);
   const inCycle: string[] = [];
   for (const node of allNodes) {
-    if (!sorted.includes(node)) {
+    if (!sortedSet.has(node)) {
       inCycle.push(node);
     }
   }

packages/static/src/build/idReplacement.test.ts

@@ -0,0 +1,77 @@
+import { describe, it, expect } from "vitest";
+import { replaceIdsInContent } from "./idReplacement";
+
+describe("replaceIdsInContent", () => {
+  it("replaces a single mapped ID", () => {
+    const idMapping = new Map([["temp-1", "final-1"]]);
+
+    const result = replaceIdsInContent("ref to temp-1 here", idMapping);
+
+    expect(result).toBe("ref to final-1 here");
+  });
+
+  it("replaces multiple different IDs in one content", () => {
+    const idMapping = new Map([
+      ["temp-1", "final-1"],
+      ["temp-2", "final-2"],
+    ]);
+
+    const result = replaceIdsInContent("temp-1 and temp-2", idMapping);
+
+    expect(result).toBe("final-1 and final-2");
+  });
+
+  it("replaces all occurrences of the same ID", () => {
+    const idMapping = new Map([["temp-1", "final-1"]]);
+
+    const result = replaceIdsInContent("temp-1, temp-1, temp-1", idMapping);
+
+    expect(result).toBe("final-1, final-1, final-1");
+  });
+
+  it("skips identity mappings", () => {
+    const idMapping = new Map([
+      ["temp-1", "temp-1"],
+      ["temp-2", "final-2"],
+    ]);
+
+    const result = replaceIdsInContent("temp-1 and temp-2", idMapping);
+
+    expect(result).toBe("temp-1 and final-2");
+  });
+
+  it("returns content unchanged when mapping is empty", () => {
+    const content = "no changes expected";
+
+    expect(replaceIdsInContent(content, new Map())).toBe(content);
+  });
+
+  it("returns content unchanged when mapping only has identity entries", () => {
+    const idMapping = new Map([["temp-1", "temp-1"]]);
+    const content = "temp-1 stays as is";
+
+    expect(replaceIdsInContent(content, idMapping)).toBe(content);
+  });
+
+  it("escapes regex special characters in IDs", () => {
+    const idMapping = new Map([["fun__rsc-payload/a.b+c(1)", "final-1"]]);
+
+    const result = replaceIdsInContent(
+      "see fun__rsc-payload/a.b+c(1) and fun__rsc-payload/aXb+c(1)",
+      idMapping,
+    );
+
+    expect(result).toBe("see final-1 and fun__rsc-payload/aXb+c(1)");
+  });
+
+  it("does not re-replace IDs produced by earlier replacements", () => {
+    const idMapping = new Map([
+      ["temp-1", "temp-2"],
+      ["temp-2", "final-2"],
+    ]);
+
+    const result = replaceIdsInContent("temp-1 temp-2", idMapping);
+
+    expect(result).toBe("temp-2 final-2");
+  });
+});

packages/static/src/build/idReplacement.ts

@@ -0,0 +1,31 @@
+/**
+ * Escapes characters that have special meaning in regular expressions.
+ */
+function escapeRegExp(str: string): string {
+  return str.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+/**
+ * Replaces temporary IDs with final hashed IDs in content.
+ *
+ * All replacements happen in a single pass over the content using one
+ * alternation regex, instead of one full-string scan per mapping entry.
+ * Identity mappings (oldId === newId) are skipped.
+ */
+export function replaceIdsInContent(
+  content: string,
+  idMapping: Map<string, string>,
+): string {
+  let pattern = "";
+  for (const [oldId, newId] of idMapping) {
+    if (oldId !== newId) {
+      pattern += (pattern === "" ? "" : "|") + escapeRegExp(oldId);
+    }
+  }
+  if (pattern === "") {
+    return content;
+  }
+  return content.replace(new RegExp(pattern, "g"), (match) =>
+    idMapping.get(match)!,
+  );
+}

packages/static/src/build/rscProcessor.ts

@@ -1,6 +1,7 @@
 import { getPayloadIDFor } from "../rsc/rscModule";
 import { computeContentHash } from "./contentHash";
 import { findReferencedIds, topologicalSort } from "./dependencyGraph";
+import { replaceIdsInContent } from "./idReplacement";
 
 export interface ProcessedComponent {
   finalId: string;
@@ -80,14 +81,8 @@ export async function processRscComponents(
   const processedComponents: ProcessedComponent[] = [];
 
   for (const tempId of sorted) {
-    let content = components.get(tempId)!;
-
     // Replace all already-finalized temp IDs with their hash-based IDs
-    for (const [oldId, newId] of idMapping) {
-      if (oldId !== newId) {
-        content = content.replaceAll(oldId, newId);
-      }
-    }
+    const content = replaceIdsInContent(components.get(tempId)!, idMapping);
 
     // Compute content hash for this component
     const contentHash = await computeContentHash(content);
@@ -105,14 +100,8 @@ export async function processRscComponents(
 
   // Add cycle members to processed components (with original IDs)
   for (const tempId of inCycle) {
-    let content = components.get(tempId)!;
-
     // Replace finalized IDs in cycle member content
-    for (const [oldId, newId] of idMapping) {
-      if (oldId !== newId) {
-        content = content.replaceAll(oldId, newId);
-      }
-    }
+    const content = replaceIdsInContent(components.get(tempId)!, idMapping);
 
     processedComponents.push({
       finalId: tempId, // Keep original temp ID