Improve veraPDF Java version error message

Author: cderv

src/tools/impl/verapdf.ts

@@ -40,8 +40,15 @@ export const verapdfInstallable: InstallableTool = {
         kSupportedJavaVersions.includes(javaVersion);
     },
     os: ["darwin", "linux", "windows"],
-    message:
-      `Java is not installed or version is not supported. veraPDF requires Java 8, 11, 17, or 21.`,
+    message: async () => {
+      const javaVersion = await getJavaVersion();
+      const supportedVersions = kSupportedJavaVersions.join(", ");
+      if (javaVersion === undefined) {
+        return `Java is not installed. veraPDF requires Java ${supportedVersions}.`;
+      } else {
+        return `Java ${javaVersion} is installed but not supported. veraPDF requires Java ${supportedVersions}.`;
+      }
+    },
   }],
   installed,
   installDir,

src/tools/tools.ts

@@ -136,7 +136,10 @@ export async function installTool(name: string, updatePath?: boolean) {
           for (const prereq of platformPrereqs) {
             const met = await prereq.check(context);
             if (!met) {
-              context.error(prereq.message);
+              const message = typeof prereq.message === "function"
+                ? await prereq.message(context)
+                : prereq.message;
+              context.error(message);
               Deno.exit(1);
             }
           }

src/tools/types.ts

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