Experiment with grouping errors in array

Fix eslint

Comment on code

Separate validation logic to lib
Unit tests

Code formatting

Use const for immutables and arrays
Multiline condition statement with brackets
Fix whitespace

Added unit tests for argument validations

Simplify validateHeaders by using lodash reduce

Fix formatting after code review

Use arrow function

Removed redundant unit tests.
Added jsdoc
Removed argument validations.

Minor comment fix.

src/core_plugins/kibana/public/management/sections/indices/add_data_steps/parse_csv_step/lib/__tests__/validate_headers.js

@@ -0,0 +1,39 @@
+import validateHeaders from '../validate_headers';
+import expect from 'expect.js';
+
+describe('validateHeaders', function () {
+
+  describe('basic validations', function () {
+
+    it('should return empty array if fields are valid', function () {
+      const errors = validateHeaders(['aa', 'bb', 'cc', 'dd', 'ee']);
+      expect(errors).to.eql([]);
+    });
+
+    it('should return empty array if it contains white space field name', function () {
+      const errors = validateHeaders(['aa', 'bb', '  ', ' ', 'ee']);
+      expect(errors.length).to.be(0);
+    });
+
+    it('should return an error if contains blank field name', function () {
+      const errors = validateHeaders(['aa', 'bb', 'cc', '', 'ee']);
+      expect(errors.length).to.be(1);
+      expect(errors[0]).eql({ type: 'blank', positions: [4] });
+    });
+
+    it('should return an error if fields contain duplicate field name', function () {
+      const errors = validateHeaders(['aa', 'bb', 'cc', 'dd', 'aa']);
+      expect(errors.length).to.be(1);
+      expect(errors[0]).eql({ type: 'duplicate', positions: [1, 5], fieldName: 'aa' });
+    });
+
+    it('should return multiple errors if fields contain duplicate and blank field name', function () {
+      const errors = validateHeaders(['aa', 'bb', '', 'dd', 'aa', '', 'aa', 'dd', 'hh']);
+      expect(errors.length).to.be(3);
+      expect(errors[0]).eql({ type: 'duplicate', positions: [1, 5, 7], fieldName: 'aa' });
+      expect(errors[1]).eql({ type: 'blank', positions: [3, 6] });
+      expect(errors[2]).eql({ type: 'duplicate', positions: [4, 8], fieldName: 'dd' });
+    });
+  });
+
+});

src/core_plugins/kibana/public/management/sections/indices/add_data_steps/parse_csv_step/lib/validate_headers.js

@@ -0,0 +1,43 @@
+import _ from 'lodash';
+
+/**
+ * @typedef error
+ * @type Object
+ * @property {String} fieldName The field name with error.
+ * @property {Number[]} positions The field positions with error. One-based.
+ * @property {String} type The type of error. Eg: duplicate, blank
+ */
+
+/**
+ * Check for errors with header fields for csv import preview.
+ * Returns an empty array if no error is found.
+ *
+ * @param {String[]} fields An array of field names
+ * @returns {error[]} errors An array of error objects
+ */
+export default function validateHeaders(fields) {
+  const errors = [];
+
+  const fieldsWithPositions = _.reduce(fields, (result, field, index) => {
+    (result[field] || (result[field] = [])).push(index + 1);
+    return result;
+  }, {});
+
+  _.forEach(fieldsWithPositions, (positions, field) => {
+    if (_.isEmpty(field)) {
+      errors.push({
+        positions: positions,
+        type: 'blank'
+      });
+    }
+    else if (positions.length > 1) {
+      errors.push({
+        fieldName: field,
+        positions: positions,
+        type: 'duplicate'
+      });
+    }
+  });
+
+  return errors;
+}

src/core_plugins/kibana/public/management/sections/indices/add_data_steps/parse_csv_step/parse_csv_step.js

@@ -1,6 +1,7 @@
 import _ from 'lodash';
 import Papa from 'papaparse';
 import modules from 'ui/modules';
+import validateHeaders from './lib/validate_headers';
 import template from './parse_csv_step.html';
 import './styles/_add_data_parse_csv_step.less';
 
@@ -67,20 +68,15 @@ modules.get('apps/management')
                   return;
                 }
                 if (row === 1) {
-                  // Collect general information on the first pass
-                  if (results.meta.fields.length > _.uniq(results.meta.fields).length) {
-                    this.formattedErrors.push('Column names must be unique');
-                  }
-
-                  let hasEmptyHeader = false;
-                  _.forEach(results.meta.fields, (field) => {
-                    if (_.isEmpty(field)) {
-                      hasEmptyHeader = true;
+                  // Check for header errors on the first row
+                  const errors = validateHeaders(results.meta.fields);
+                  _.forEach(errors, (error) => {
+                    if (error.type === 'duplicate') {
+                      this.formattedErrors.push(`Columns at positions [${error.positions}] have duplicate name "${error.fieldName}"`);
+                    } else if (error.type === 'blank') {
+                      this.formattedErrors.push(`Columns at positions [${error.positions}] must not be blank`);
                     }
                   });
-                  if (hasEmptyHeader) {
-                    this.formattedErrors.push('Column names must not be blank');
-                  }
 
                   if (results.meta.fields.length > maxSampleColumns) {
                     this.formattedWarnings.push(`Preview truncated to ${maxSampleColumns} columns`);