fileInput JS: Allow uploading the same file. (#1719)

* tools README: notes about entr + grunt

* fileInput JS: Allow uploading the same file. Fixes #1508

* Grunt

* Added note to NEWS.

* tools README: add Linux section, fix formatting

NEWS.md

@@ -9,6 +9,8 @@ shiny 1.0.3.9000
 
 ### Minor new features and improvements
 
+* Addressed [#1508](https://github.com/rstudio/shiny/issues/1508): `fileInput` now permits the same file to be uploaded multiple times. ([#1719](https://github.com/rstudio/shiny/pull/1719))
+
 * Addressed [#1501](https://github.com/rstudio/shiny/issues/1501): The `fileInput` control now retains uploaded file extensions on the server. This fixes [readxl](https://github.com/tidyverse/readxl)'s `readxl::read_excel` and other functions that must recognize a file's extension in order to work. ([#1706](https://github.com/rstudio/shiny/pull/1706))
 
 * For `conditionalPanel`s, Shiny now gives more informative messages if there are errors evaluating or parsing the JavaScript conditional expression. ([#1727](https://github.com/rstudio/shiny/pull/1727))

inst/www/shared/shiny.js

@@ -4843,6 +4843,9 @@ var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol
         // invalidated reactives, but observers don't actually execute.
         self.shinyapp.makeRequest('uploadieFinish', [], function () {}, function () {});
         $(self.iframe).remove();
+        // Reset the file input's value to "". This allows the same file to be
+        // uploaded again. https://stackoverflow.com/a/22521275
+        $(self.fileEl).val("");
       };
       if (this.iframe.attachEvent) {
         this.iframe.attachEvent('onload', iframeDestroy);
@@ -4958,6 +4961,9 @@ var _typeof = typeof Symbol === "function" && typeof Symbol.iterator === "symbol
         self.$setActive(false);
         self.onProgress(null, 1);
         self.$bar().text('Upload complete');
+        // Reset the file input's value to "". This allows the same file to be
+        // uploaded again. https://stackoverflow.com/a/22521275
+        $(evt.el).val("");
       }, function (error) {
         self.onError(error);
       });

srcjs/input_binding_fileinput.js

@@ -19,6 +19,9 @@ var IE8FileUploader = function(shinyapp, id, fileEl) {
       // invalidated reactives, but observers don't actually execute.
       self.shinyapp.makeRequest('uploadieFinish', [], function(){}, function(){});
       $(self.iframe).remove();
+      // Reset the file input's value to "". This allows the same file to be
+      // uploaded again. https://stackoverflow.com/a/22521275
+      $(self.fileEl).val("");
     };
     if (this.iframe.attachEvent) {
       this.iframe.attachEvent('onload', iframeDestroy);
@@ -142,6 +145,9 @@ $.extend(FileUploader.prototype, FileProcessor.prototype);
         self.$setActive(false);
         self.onProgress(null, 1);
         self.$bar().text('Upload complete');
+        // Reset the file input's value to "". This allows the same file to be
+        // uploaded again. https://stackoverflow.com/a/22521275
+        $(evt.el).val("");
       },
       function(error) {
         self.onError(error);

tools/README.md

@@ -84,7 +84,23 @@ One of the tasks concatenates all the .js files in `/srcjs` together into `/inst
 
 During development of Shiny's Javascript code, it's best to use `grunt watch` so that the minified file will get updated whenever you make changes the Javascript sources.
 
+#### Auto build and browser refresh
 
+An alternative to `grunt watch` is to use `entr` to trigger `grunt` when sources change. `entr` can be installed with `brew install entr` on a Mac, or on Linux using your distribution's package manager. Using this technique, it's possible to both automatically rebuild sources and reload Chrome at the same time:
+
+*macOS*:
+
+```
+find ../srcjs/ | entr bash -c './node_modules/grunt/bin/grunt && osascript -e "tell application \"Google Chrome\" to reload active tab of window 1"'
+```
+
+*Linux*:
+
+For this to work you must first install `xdotool` using your distribution's package manager.
+
+```
+find ../srcjs/ | entr bash -c './node_modules/grunt/bin/grunt && xdotool search --onlyvisible --class Chrome windowfocus key ctrl+r'
+```
 
 Updating web libraries
 ======================