Repository: gregnb/mui-datatables (js)

Issue:
[Bug][Per page] Page is greater than the total available
<!--- Provide a general summary of the issue in the Title above -->
There is an exception, when I try to change "per page" option in the MUITable at the last page (data length equals to 29, and we change per page from 10 items to 15 items, and expect total 2 pages, but got the exception: ```Provided options.page of `2` is greater than the total available page length of `1` ```)
Btw, if data length equals to 30, there are no exceptions in this case.

Such problem already have been solved at #48, but seems not at all.
 
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## Expected Behavior
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    If you're describing a bug, tell us what should happen.
    If you're suggesting a change/improvement, tell us how it should work.
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We don't have an exception, and can see 2 pages with our data

## Current Behavior
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    If describing a bug, tell us what happens instead of the expected behavior.
    If suggesting a change/improvement, explain the difference from current behavior.
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We have exception on display ```Provided options.page of `2` is greater than the total available page length of `1` ```

## Steps to Reproduce (for bugs)
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Live example: https://codesandbox.io/s/6vlml849zk

1. Go to last page (page number 3)
2. Change option "per page" from "10" to "15"
3. Boom!

## Your Environment
<!--- Include as many relevant details about the environment with which you experienced the bug. -->

| Tech         | Version |
|--------------|---------|
| Material-UI  |    1.4.0     |
| MUI-datatables  |     ^2.0.0-beta-32    |
| React        |    16.5.0     |
| browser      |    Chrome     |

Pull request description:
Fix for changing rows per page issue
Fix `MUIDataTable` changeRowsPerPage method

After merge it will fix #242

Patch:
diff --git a/.gitignore b/.gitignore
index dbea00b..6f2b7bf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,6 +10,9 @@ npm-debug.log*
 *.sublime-project
 *.sublime-workspace
 
+# vscode project
+.vscode
+
 # Runtime data
 pids
 *.pid
diff --git a/src/MUIDataTable.js b/src/MUIDataTable.js
index 03620cf..612de23 100644
--- a/src/MUIDataTable.js
+++ b/src/MUIDataTable.js
@@ -540,9 +540,17 @@ class MUIDataTable extends React.Component {
   };
 
   changeRowsPerPage = rows => {
+    /**
+     * After changing rows per page recalculate totalPages and checks its if current page not higher.
+     * Otherwise sets current page the value of nextTotalPages
+     */
+    const rowCount = this.options.count || this.state.displayData.length;
+    const nextTotalPages = Math.floor(rowCount / rows);
+
     this.setState(
       () => ({
         rowsPerPage: rows,
+        page: this.state.page > nextTotalPages ? nextTotalPages : this.state.page,
       }),
       () => {
         this.setTableAction("changeRowsPerPage");


Test patch:
diff --git a/test/MUIDataTable.test.js b/test/MUIDataTable.test.js
index 132bbc2..390979a 100644
--- a/test/MUIDataTable.test.js
+++ b/test/MUIDataTable.test.js
@@ -381,6 +381,18 @@ describe("<MUIDataTable />", function() {
     assert.deepEqual(state.rowsPerPage, 10);
   });
 
+  it("should recalculate page when calling changeRowsPerPage method", () => {
+    const data = new Array(29).fill("").map(() => ["Joe James", "Test Corp", "Yonkers", "NY"]);
+    const mountWrapper = mount(shallow(<MUIDataTable columns={columns} data={data} />).get(0));
+    const instance = mountWrapper.instance();
+
+    instance.changePage(2);
+    instance.changeRowsPerPage(15);
+
+    const state = mountWrapper.state();
+    assert.equal(state.page, 1);
+  });
+
   it("should update page position when calling changePage method", () => {
     const shallowWrapper = shallow(<MUIDataTable columns={columns} data={data} />).dive();
     const instance = shallowWrapper.instance();