HTML writer: emit empty alt tag in figures (#5518)

The same text is already in the <figcaption> and
screen-readers would read it twice, see #4737

src/Text/Pandoc/Writers/HTML.hs

@@ -681,7 +681,7 @@ figure :: PandocMonad m
        => WriterOptions -> Attr -> [Inline] -> (String, String)
        -> StateT WriterState m Html
 figure opts attr txt (s,tit) = do
-  img <- inlineToHtml opts (Image attr txt (s,tit))
+  img <- inlineToHtml opts (Image attr [Str ""] (s,tit))
   html5 <- gets stHtml5
   let tocapt = if html5
                   then H5.figcaption

test/command/3577.md

@@ -16,10 +16,10 @@
 \end{figure}
 ^D
 <figure>
-<img src="img1.jpg" alt="Caption 1" /><figcaption>Caption 1</figcaption>
+<img src="img1.jpg" alt="" /><figcaption>Caption 1</figcaption>
 </figure>
 <figure>
-<img src="img2.jpg" alt="Caption 2" /><figcaption>Caption 2</figcaption>
+<img src="img2.jpg" alt="" /><figcaption>Caption 2</figcaption>
 </figure>
 ```
 ```
@@ -30,6 +30,6 @@
 \end{figure}
 ^D
 <figure>
-<img src="img1.jpg" alt="Caption 3" /><figcaption>Caption 3</figcaption>
+<img src="img1.jpg" alt="" /><figcaption>Caption 3</figcaption>
 </figure>
 ```

test/command/4677.md

@@ -3,6 +3,6 @@
 ![Caption](img.png){#img:1}
 ^D
 <figure>
-<img src="img.png" alt="Caption" id="img:1" /><figcaption>Caption</figcaption>
+<img src="img.png" alt="" id="img:1" /><figcaption>Caption</figcaption>
 </figure>
 ```

test/command/5121.md

@@ -5,7 +5,7 @@
 ## Header 2
 ^D
 <figure>
-<img src="./my-figure.jpg" alt="My caption" width="500" /><figcaption>My caption</figcaption>
+<img src="./my-figure.jpg" alt="" width="500" /><figcaption>My caption</figcaption>
 </figure>
 
 Header 2

test/writer.html4

@@ -518,7 +518,7 @@ Blah
 <h1 id="images">Images</h1>
 <p>From “Voyage dans la Lune” by Georges Melies (1902):</p>
 <div class="figure">
-<img src="lalune.jpg" title="Voyage dans la Lune" alt="lalune" />
+<img src="lalune.jpg" title="Voyage dans la Lune" alt="" />
 <p class="caption">lalune</p>
 </div>
 <p>Here is a movie <img src="movie.jpg" alt="movie" /> icon.</p>

test/writer.html5

@@ -521,7 +521,7 @@ Blah
 <h1 id="images">Images</h1>
 <p>From “Voyage dans la Lune” by Georges Melies (1902):</p>
 <figure>
-<img src="lalune.jpg" title="Voyage dans la Lune" alt="lalune" /><figcaption>lalune</figcaption>
+<img src="lalune.jpg" title="Voyage dans la Lune" alt="" /><figcaption>lalune</figcaption>
 </figure>
 <p>Here is a movie <img src="movie.jpg" alt="movie" /> icon.</p>
 <hr />