improve require() failure messages

oracledb.js.diff

diff --git a/lib/oracledb.js b/lib/oracledb.js
index 10025481..869a6fb2 100644
--- a/lib/oracledb.js
+++ b/lib/oracledb.js
@@ -41,28 +41,32 @@ var binaryDebugPath = '../build/Debug/oracledb.node';
 try {
   oracledbCLib =  require(binaryReleasePath);
 } catch (err) {
-  if (err.code !== 'MODULE_NOT_FOUND') {
-    throw err;
-  } else {
+  var nodeInfo = process.versions.node + ' (' + process.platform + ', ' + process.arch +')\n';
+  var fullReleasePath = require('path').resolve(__dirname, binaryReleasePath);
+  if (err.code === 'MODULE_NOT_FOUND') {
     try {
       oracledbCLib = require(binaryDebugPath);
     } catch (err) {
-      if (err.code !== 'MODULE_NOT_FOUND') {
-        throw err;
+      if (err.code === 'MODULE_NOT_FOUND') {
+        // Neither Release or Debug binary was found but assume users wanted Release binary
+        nodeInfo += 'Cannot find module ' + fullReleasePath + '\n' + getInfo();
+        throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
       } else {
-        var nodeInfo = process.versions.node + ' (' + process.platform + ', ' + process.arch +')\n';
-        var fullPath = require('path').resolve(__dirname, binaryReleasePath);
-        try {
-          require('fs').statSync(fullPath);
-          nodeInfo += getInfo();  // file exists, so get message about Oracle Client
-          throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
-        } catch(err) {
-          // file couldn't be found
-          nodeInfo += 'Cannot read ' + fullPath + '\n' + err.message;
-          throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
-        }
+        nodeInfo += 'Cannot load ' + binaryDebugPath + '\n';
+        nodeInfo += 'Node.js require() error was: \n  ' + err.message + '\n' + getInfo();
+        throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
       }
     }
+  } else {
+    if (err.message.startsWith('DPI-1047:')) {
+      // Release add-on binary loaded OK, but ODPI-C can't load Oracle client
+      nodeInfo += 'Node.js require() error was: \n  ' + err.message + '\n';
+      nodeInfo += 'Node.js require() mapped to ' + fullReleasePath + '\n' + getInfo();
+      throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
+    } else {
+      nodeInfo += 'Cannot load ' + fullReleasePath + '\n' + err.message + '\n' + getInfo();
+      throw new Error(nodbUtil.getErrorMessage('NJS-045', nodeInfo));
+    }
   }
 }
 
@@ -72,9 +76,10 @@ oracledbCLib.Oracledb.prototype.newLob = function(iLob) {
 
 
 // Return a string with installation usage tips that may be helpful
-// (although ODPI-C should catch most cases)
 function getInfo() {
   var arch, url, mesg = '';
+  mesg = 'Node-oracledb installation instructions: ';
+  mesg += 'https://github.com/oracle/node-oracledb/blob/master/INSTALL.md\n';
   if (process.platform === 'linux') {
     if (process.arch === 'x64') {
       url = 'http://www.oracle.com/technetwork/topics/linuxx86-64soft-092277.html\n';
@@ -84,14 +89,13 @@ function getInfo() {
       arch = '32-bit';
     }
     mesg += 'You must have ' + arch + ' Oracle client libraries in LD_LIBRARY_PATH, or configured with ldconfig.\n';
-    mesg += 'If you do not already have libraries, install the Instant Client Basic or Basic Light package from \n';
+    mesg += 'If you do not have Oracle Database on this computer, then install the Instant Client Basic or Basic Light package from \n';
     mesg += url;
   } else if (process.platform === 'darwin') {
+    url = 'http://www.oracle.com/technetwork/topics/intel-macsoft-096467.html';
     if (process.arch === 'x64') {
-      url = 'http://www.oracle.com/technetwork/topics/winx64soft-089540.html';
       arch = '64-bit';
     } else {
-      url = 'http://www.oracle.com/technetwork/topics/winsoft-085727.html';
       arch = '32-bit';
     }
     mesg += 'You must have the ' + arch + ' Oracle Instant Client Basic or Basic Light package in ~/lib or /usr/local/lib\n';
@@ -105,7 +109,7 @@ function getInfo() {
       arch = '32-bit';
     }
     mesg += 'You must have ' + arch + ' Oracle client libraries in your PATH environment variable.\n';
-    mesg += 'If you do not already have libraries, install the Instant Client Basic or Basic Light package from\n';
+    mesg += 'If you do not have Oracle Database on this computer, then install the Instant Client Basic or Basic Light package from\n';
     mesg += url;
     mesg += 'A Microsoft Visual Studio Redistributable suitable for your Oracle client library version must be available.\n';
   } else {
@@ -116,11 +120,9 @@ function getInfo() {
       arch = '32-bit';
     }
     mesg += 'You must have ' + arch + ' Oracle client libraries in your operating system library search path.\n';
-    mesg += 'If you do not already have libraries, install an Instant Client Basic or Basic Light package from: \n';
+    mesg += 'If you do not have Oracle Database on this computer, then install an Instant Client Basic or Basic Light package from: \n';
     mesg += url;
   }
-  mesg += 'Node-oracledb installation instructions: ';
-  mesg += 'https://github.com/oracle/node-oracledb/blob/master/INSTALL.md\n\n';
   return mesg;
 }