From f9462973263f9dd23bcb945c65cbacb7cc85bade Mon Sep 17 00:00:00 2001
From: christophe dervieux <christophe.dervieux@gmail.com>
Date: Thu, 23 Apr 2026 16:44:54 +0200
Subject: [PATCH 1/2] Warn and skip preview build when npm is missing during
 configure

Check for npm at the start of configure() instead of failing late in
buildQuartoPreviewJs() after ~300MB of downloads. When npm is missing,
emit a warning explaining that the quarto preview live-reload feature
will not be available, then skip the quarto-preview.js build step.
The rest of Quarto (render, pdf, publish) builds and runs normally.
---
 package/src/common/configure.ts | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/package/src/common/configure.ts b/package/src/common/configure.ts
index f8406df08b..b3e12458c1 100644
--- a/package/src/common/configure.ts
+++ b/package/src/common/configure.ts
@@ -18,13 +18,25 @@ import {
   configureDependency,
   kDependencies,
 } from "./dependencies/dependencies.ts";
-import { suggestUserBinPaths } from "../../../src/core/path.ts";
+import { suggestUserBinPaths, which } from "../../../src/core/path.ts";
 import { buildQuartoPreviewJs } from "./previewjs.ts";
 import { isWindows } from "../../../src/deno_ral/platform.ts";
 
 export async function configure(
   config: Configuration,
 ) {
+  // npm is only required for building quarto-preview.js (used by `quarto preview`
+  // for HTML/revealjs live-reload). Warn upfront so the user knows before the
+  // long dependency downloads; the JS build is skipped below if npm is missing.
+  const hasNpm = (await which("npm")) !== undefined;
+  if (!hasNpm) {
+    warning(
+      "npm not found on PATH. The 'quarto preview' live-reload feature " +
+        "will not be available. Install Node.js (which provides npm) and " +
+        "re-run configure to enable it.",
+    );
+  }
+
   // Download dependencies
   for (const dependency of kDependencies) {
     const targetDir = join(
@@ -34,12 +46,16 @@ export async function configure(
     await configureDependency(dependency, targetDir, config);
   }
 
-  info("Building quarto-preview.js...");
-  const result = buildQuartoPreviewJs(config.directoryInfo.src);
-  if (!result.success) {
-    throw new Error();
+  if (hasNpm) {
+    info("Building quarto-preview.js...");
+    const result = buildQuartoPreviewJs(config.directoryInfo.src);
+    if (!result.success) {
+      throw new Error();
+    }
+    info("Build completed.");
+  } else {
+    info("Skipping quarto-preview.js build (npm not found).");
   }
-  info("Build completed.");
 
   // Move the quarto script into place
   info("Placing Quarto script");

From 52f6a76221e17b3b839e7db225fa65404c7bd47c Mon Sep 17 00:00:00 2001
From: christophe dervieux <christophe.dervieux@gmail.com>
Date: Thu, 23 Apr 2026 18:25:08 +0200
Subject: [PATCH 2/2] Error out instead of skipping when npm is missing

A half-built Quarto without quarto-preview.js would later fail at
runtime when `quarto preview` tries to read the missing file, producing
another confusing error. Requiring npm upfront keeps the contract
simple: configure succeeds only if all required tools are available.
---
 package/src/common/configure.ts | 29 +++++++++++------------------
 1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/package/src/common/configure.ts b/package/src/common/configure.ts
index b3e12458c1..a40b185fa8 100644
--- a/package/src/common/configure.ts
+++ b/package/src/common/configure.ts
@@ -25,15 +25,12 @@ import { isWindows } from "../../../src/deno_ral/platform.ts";
 export async function configure(
   config: Configuration,
 ) {
-  // npm is only required for building quarto-preview.js (used by `quarto preview`
-  // for HTML/revealjs live-reload). Warn upfront so the user knows before the
-  // long dependency downloads; the JS build is skipped below if npm is missing.
-  const hasNpm = (await which("npm")) !== undefined;
-  if (!hasNpm) {
-    warning(
-      "npm not found on PATH. The 'quarto preview' live-reload feature " +
-        "will not be available. Install Node.js (which provides npm) and " +
-        "re-run configure to enable it.",
+  // npm is required later for building quarto-preview.js (used by `quarto
+  // preview` live-reload). Check upfront to fail fast before downloading
+  // hundreds of MB of dependencies when npm is missing.
+  if ((await which("npm")) === undefined) {
+    throw new Error(
+      "npm not found on PATH. Please install Node.js (which provides npm) before running configure.",
     );
   }
 
@@ -46,16 +43,12 @@ export async function configure(
     await configureDependency(dependency, targetDir, config);
   }
 
-  if (hasNpm) {
-    info("Building quarto-preview.js...");
-    const result = buildQuartoPreviewJs(config.directoryInfo.src);
-    if (!result.success) {
-      throw new Error();
-    }
-    info("Build completed.");
-  } else {
-    info("Skipping quarto-preview.js build (npm not found).");
+  info("Building quarto-preview.js...");
+  const result = buildQuartoPreviewJs(config.directoryInfo.src);
+  if (!result.success) {
+    throw new Error();
   }
+  info("Build completed.");
 
   // Move the quarto script into place
   info("Placing Quarto script");