fix(src/plugins/utils/findOctetSequencePaths.js): Show path to erring…

… element on exception

Recently, I ran across an issue where [if the validator throws an exception in a specific part of
the code, the path to the exception-causing code is
swallowed](#180). After a moderate amount of digging,
I decided that an option for providing more information about this code would be to put the path to
the problematic element or elements into the exception message. This exception message is displayed
whenever the code crashes out. So, for example, the previous error message output by lint-openapi
would say "Cannot read property 'type' of null", whereas the new error would list the full path to
the type that was causing the exception.

re #180

src/plugins/utils/findOctetSequencePaths.js

@@ -35,12 +35,36 @@ function arrayOctetSequences(resolvedSchema, path) {
     const pathToSchema = Array.isArray(path)
       ? path.concat('items')
       : `${path}.items`;
-    if (arrayItems.type === 'string' && arrayItems.format === 'binary') {
-      arrayPathsToOctetSequence.push(pathToSchema);
-    } else if (arrayItems.type === 'object' || arrayItems.type === 'array') {
-      arrayPathsToOctetSequence.push(
-        ...findOctetSequencePaths(arrayItems, pathToSchema)
-      );
+    try {
+      if (arrayItems.type === 'string' && arrayItems.format === 'binary') {
+        arrayPathsToOctetSequence.push(pathToSchema);
+      } else if (arrayItems.type === 'object' || arrayItems.type === 'array') {
+        arrayPathsToOctetSequence.push(
+          ...findOctetSequencePaths(arrayItems, pathToSchema)
+        );
+      }
+    } catch(err) {
+      if (err instanceof TypeError) {
+        var escapedPaths = [];
+        const strEscaper = function(strToEscape) {
+          var newStr = "";
+          for (i=0;i<strToEscape.length;i++) {
+            if (strToEscape.charAt(i) == "/") {
+              newStr = newStr + "\\/";
+            } else {
+              newStr = newStr + strToEscape.charAt(i);
+            }
+          }
+          escapedPaths.push(newStr);
+        };
+        path.forEach(strEscaper);
+        var e = new TypeError("items.type and items.format must resolve for the path \"" + escapedPaths.join("/") + "\"");
+        e.stack = err.stack;
+        e.original = err;
+        throw e;
+      } else {
+        throw err;
+      }
     }
   }
   return arrayPathsToOctetSequence;