Improve error messages

Lazy evaluation has made it more difficult to track down the source of
errors because all operations on a dataset are chained together and
executed at once. This adds a prefix to any errors emitted by GDAL that
explains where the error occurred.

src/wrappers/gdalClose.js

@@ -14,13 +14,14 @@ export default function (GDALClose, errorHandling) {
         let errorType = errorHandling.CPLGetLastErrorType();
 
         // Check for errors; throw if error is detected
+        // Note that due to https://github.com/ddohler/gdal-js/issues/38 this can only check for
+        // CEFatal errors in order to avoid raising an exception on GDALClose
         if (
-            errorType === errorHandling.CPLErr.CEFailure ||
             errorType === errorHandling.CPLErr.CEFatal
         ) {
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALClose: ' + message);
         } else {
             return result;
         }

src/wrappers/gdalGetGeoTransform.js

@@ -33,10 +33,10 @@ export default function (GDALGetGeoTransform, errorHandling) {
             Module._free(byteOffset);
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALGetGeoTransform: ' + message);
         } else {
-            // To avoid memory leaks in the Emscripten heap, we need to free up the memory we allocated
-            // after we've converted it into a Javascript object.
+            // To avoid memory leaks in the Emscripten heap, we need to free up the memory we
+            // allocated after we've converted it into a Javascript object.
             let result = Array.from(geoTransform);
 
             Module._free(byteOffset);

src/wrappers/gdalGetProjectionRef.js

@@ -11,7 +11,7 @@ export default function (GDALGetProjectionRef, errorHandling) {
         ) {
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALGetProjectionRef: ' + message);
         } else {
             return result;
         }

src/wrappers/gdalGetRasterCount.js

@@ -11,7 +11,7 @@ export default function (GDALGetRasterCount, errorHandling) {
         ) {
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALGetRasterCount: ' + message);
         } else {
             return result;
         }

src/wrappers/gdalGetRasterXSize.js

@@ -11,7 +11,7 @@ export default function (GDALGetRasterXSize, errorHandling) {
         ) {
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALGetRasterXSize: ' + message);
         } else {
             return result;
         }

src/wrappers/gdalGetRasterYSize.js

@@ -11,7 +11,7 @@ export default function (GDALGetRasterYSize, errorHandling) {
         ) {
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw Error(message);
+            throw Error('Error in GDALGetRasterYSize: ' + message);
         } else {
             return result;
         }

src/wrappers/gdalOpen.js

@@ -31,7 +31,7 @@ export default function (GDALOpen, errorHandling, rootPath) {
             FS.rmdir(directory);
             let message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALOpen: ' + message);
         } else {
             return {
                 datasetPtr: datasetPtr,

src/wrappers/gdalRasterize.js

@@ -40,11 +40,12 @@ export default function (GDALRasterize, errorHandling, rootPath) {
             params.deallocate();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALRasterize: ' + message);
         }
 
-        // Now that we have our translate options, we need to make a file location to hold the output.
-        let directory = rootPath + '/' + randomKey();
+        // Now that we have our translate options, we need to make a file location to hold the
+        // output.
+        let directory = rootPath + randomKey();
 
         FS.mkdir(directory);
         // This makes it easier to remove later because we can just unmount rather than recursing
@@ -93,7 +94,7 @@ export default function (GDALRasterize, errorHandling, rootPath) {
             cleanUp();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALRasterize: ' + message);
         } else {
             const result = {
                 datasetPtr: newDatasetPtr,

src/wrappers/gdalTranslate.js

@@ -31,11 +31,12 @@ export default function (GDALTranslate, errorHandling, rootPath) {
             params.deallocate();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALTranslate: ' + message);
         }
 
-        // Now that we have our translate options, we need to make a file location to hold the output.
-        let directory = rootPath + '/' + randomKey();
+        // Now that we have our translate options, we need to make a file location to hold the
+        // output.
+        let directory = rootPath + randomKey();
 
         FS.mkdir(directory);
         // This makes it easier to remove later because we can just unmount rather than recursing
@@ -75,7 +76,7 @@ export default function (GDALTranslate, errorHandling, rootPath) {
             cleanUp();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALTranslate: ' + message);
         } else {
             const result = {
                 datasetPtr: newDatasetPtr,

src/wrappers/gdalWarp.js

@@ -31,10 +31,10 @@ export default function (GDALWarp, errorHandling, rootPath) {
             params.deallocate();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALWarp: ' + message);
         }
 
-        let directory = rootPath + '/' + randomKey();
+        let directory = rootPath + randomKey();
 
         FS.mkdir(directory);
         // This makes it easier to remove later because we can just unmount rather than recursing
@@ -58,7 +58,8 @@ export default function (GDALWarp, errorHandling, rootPath) {
         // at a time, we don't need to do anything fancy here.
         let datasetListPtr = Module._malloc(4); // 32-bit pointer
 
-        Module.setValue(datasetListPtr, dataset, '*'); // Set datasetListPtr to the address of dataset
+        // Set datasetListPtr to the address of dataset
+        Module.setValue(datasetListPtr, dataset, '*');
         let newDatasetPtr = GDALWarp(
             filePath, // Output
             0, // NULL because filePath is not NULL
@@ -87,7 +88,7 @@ export default function (GDALWarp, errorHandling, rootPath) {
             cleanUp();
             const message = errorHandling.CPLGetLastErrorMsg();
 
-            throw new Error(message);
+            throw new Error('Error in GDALWarp: ' + message);
         } else {
             const result = {
                 datasetPtr: newDatasetPtr,