Add show metadata button back to the explore view (#6911)

* Add show metadata button back to the explore view

- Add the show metadta button, accidentally removed from PR #6046, back to the explore view
- Remove dead code that is no longer reachable from DataSourceModal.jsx.

* Adding additional code back to make the button function and remove more dead code.

superset/assets/src/datasource/DatasourceModal.jsx

@@ -49,10 +49,8 @@ class DatasourceModal extends React.PureComponent {
     super(props);
     this.state = {
       errors: [],
-      showDatasource: false,
       datasource: props.datasource,
     };
-    this.toggleShowDatasource = this.toggleShowDatasource.bind(this);
     this.setSearchRef = this.setSearchRef.bind(this);
     this.onDatasourceChange = this.onDatasourceChange.bind(this);
     this.onClickSave = this.onClickSave.bind(this);
@@ -111,10 +109,6 @@ class DatasourceModal extends React.PureComponent {
     this.dialog = ref;
   }
 
-  toggleShowDatasource() {
-    this.setState({ showDatasource: !this.state.showDatasource });
-  }
-
   renderSaveDialog() {
     return (
       <div>

superset/assets/src/explore/components/controls/DatasourceControl.jsx

@@ -19,13 +19,19 @@
 import React from 'react';
 import PropTypes from 'prop-types';
 import {
+  Col,
+  Collapse,
   Label,
   OverlayTrigger,
+  Row,
   Tooltip,
+  Well,
 } from 'react-bootstrap';
 import { t } from '@superset-ui/translation';
 
 import ControlHeader from '../ControlHeader';
+import ColumnOption from '../../../components/ColumnOption';
+import MetricOption from '../../../components/MetricOption';
 import DatasourceModal from '../../../datasource/DatasourceModal';
 
 const propTypes = {
@@ -52,25 +58,51 @@ class DatasourceControl extends React.PureComponent {
     };
     this.toggleShowDatasource = this.toggleShowDatasource.bind(this);
     this.toggleEditDatasourceModal = this.toggleEditDatasourceModal.bind(this);
-  }
-
-  onChange(vizType) {
-    this.props.onChange(vizType);
-    this.setState({ showModal: false });
+    this.renderDatasource = this.renderDatasource.bind(this);
   }
 
   toggleShowDatasource() {
     this.setState(({ showDatasource }) => ({ showDatasource: !showDatasource }));
   }
 
-  toggleModal() {
-    this.setState(({ showModal }) => ({ showModal: !showModal }));
-  }
   toggleEditDatasourceModal() {
     this.setState(({ showEditDatasourceModal }) => ({
       showEditDatasourceModal: !showEditDatasourceModal,
     }));
   }
+  renderDatasource() {
+    const datasource = this.props.datasource;
+    return (
+      <div className="m-t-10">
+        <Well className="m-t-0">
+          <div className="m-b-10">
+            <Label>
+              <i className="fa fa-database" /> {datasource.database.backend}
+            </Label>
+            {` ${datasource.database.name} `}
+          </div>
+          <Row className="datasource-container">
+            <Col md={6}>
+              <strong>Columns</strong>
+              {datasource.columns.map(col => (
+                <div key={col.column_name}>
+                  <ColumnOption showType column={col} />
+                </div>
+              ))}
+            </Col>
+            <Col md={6}>
+              <strong>Metrics</strong>
+              {datasource.metrics.map(m => (
+                <div key={m.metric_name}>
+                  <MetricOption metric={m} showType />
+                </div>
+              ))}
+            </Col>
+          </Row>
+        </Well>
+      </div>
+    );
+  }
   render() {
     return (
       <div>
@@ -85,6 +117,21 @@ class DatasourceControl extends React.PureComponent {
             {this.props.datasource.name}
           </Label>
         </OverlayTrigger>
+        <OverlayTrigger
+          placement="right"
+          overlay={
+            <Tooltip id={'toggle-datasource-tooltip'}>
+              {t('Expand/collapse datasource configuration')}
+            </Tooltip>
+          }
+        >
+          <a href="#">
+            <i
+              className={`fa fa-${this.state.showDatasource ? 'minus' : 'plus'}-square m-r-5`}
+              onClick={this.toggleShowDatasource}
+            />
+          </a>
+        </OverlayTrigger>
         {this.props.datasource.type === 'table' &&
           <OverlayTrigger
             placement="right"
@@ -102,6 +149,7 @@ class DatasourceControl extends React.PureComponent {
               <i className="fa fa-flask m-r-5" />
             </a>
           </OverlayTrigger>}
+        <Collapse in={this.state.showDatasource}>{this.renderDatasource()}</Collapse>
         <DatasourceModal
           datasource={this.props.datasource}
           show={this.state.showEditDatasourceModal}