Cache Java version to avoid redundant subprocess call

The check and message functions were both calling getJavaVersion(),
spawning the subprocess twice. This created inefficiency and a TOCTOU
risk where the Java environment could change between calls.

Now check caches the detected version in context.props.javaVersion,
and message reads from the cache. The message function is now
synchronous since it only reads from context.

The InstallPreReq.message type was updated to allow both sync and
async functions for flexibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cderv

src/tools/impl/verapdf.ts

@@ -34,14 +34,15 @@ const kVersionFileName = "version";
 export const verapdfInstallable: InstallableTool = {
   name: "VeraPDF",
   prereqs: [{
-    check: async () => {
+    check: async (context) => {
       const javaVersion = await getJavaVersion();
+      context.props.javaVersion = javaVersion;
       return javaVersion !== undefined &&
         kSupportedJavaVersions.includes(javaVersion);
     },
     os: ["darwin", "linux", "windows"],
-    message: async () => {
-      const javaVersion = await getJavaVersion();
+    message: (context) => {
+      const javaVersion = context.props.javaVersion as number | undefined;
       const supportedVersions = kSupportedJavaVersions.join(", ");
       if (javaVersion === undefined) {
         return `Java is not installed. veraPDF requires Java ${supportedVersions}.`;

src/tools/types.ts

@@ -30,7 +30,7 @@ export interface InstallableTool {
 export interface InstallPreReq {
   check: (context: InstallContext) => Promise<boolean>;
   os: string[];
-  message: string | ((context: InstallContext) => Promise<string>);
+  message: string | ((context: InstallContext) => string | Promise<string>);
 }
 
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