How to morph a path data to another path data in SVG?

I'm trying to figure out why it wont morph this path data to another path data, I need to make it look like an real animation.

This is my SMIL code:

    <animate xlink:href="#Barra3"  
    repeatCount="indefinite" 
    attributeName="d" 
    dur="5s"
    values="M52,346L56,346C61.523,346 66,350.477 66,356L42,356C42,350.477 46.477,346 52,346Z;
    M54,225C60.627,225 66,230.373 66,237L66,356L42,356L42,237C42,230.373 47.373,225 54,225Z;"/>

Here is my codepen:

https://codepen.io/joannesalfa/pen/mdPBJxq and go line 181. I'm using SMIL.

Solution

The most important when trying to morph a path in svg is thast the d attribute hes to have the same number of commands and the same commands. I've rewritten the short path so that the lines drawing the sides of the shape have a length = 0.

M54,346
C60.627,346,66,351.373,66,358
L66,358L42,358L42,358
C42,351.373,47.373,346,54,346Z

Please take a look:

svg{border:solid}

<svg viewBox="5 200 100 200" width="100">


  <path d="M54,346
          C60.627,346,66,351.373,66,358
          L66,358L42,358L42,358
          C42,351.373,47.373,346,54,346Z"  stroke="red" fill="gold" >

  <animate  dur='5s'
    attributeType="XML"
    attributeName='d'      
    repeatCount='indefinite'
           values="M54,225
           C60.627,225 66,230.373 66,236
           L66,356L42,356L42,236
           C42,230.373 47.373,225 54,225Z;
                                                                     
           M54,346
           C60.627,346,66,351.373,66,356
           L66,356L42,356L42,356
           C42,351.373,47.373,346,54,346Z;
                                                                                  M54,225
           C60.627,225 66,230.373 66,236
           L66,356L42,356L42,236
           C42,230.373 47.373,225 54,225Z" />
    
    </path>
</svg>

Update

The OP is commenting:

Would you mind how to rewrite the short path step by step? I find it's very confusing to me

I'm taking both those paths and I'm breaking them in 5 paths of different colors, one for every command. Please note that I had to add a move to command (M) at the beginning of each path. The value for the move to is the last point of the previous path. The lines, are the blue paths.

For the short path you can see those blue paths in the code but not in the svg because their length is 0. I needed those 0 length lines because you have lines in the long path.

svg{width:200px;border:solid;overflow:visible; fill:none}

<svg viewBox="40 220 28 140" >
  <desc>The short path</desc>
  <path d="M54,346 C60.627,346,66,351.373,66,356" stroke="red" /> 
  <path d="M66,356 L66,356" stroke="blue" />           
  <path d="M66,356 L42,356" stroke="green" />    
  <path d="M42,356 L42,356" stroke="blue" /> 
  <path d="M42,356 C42,351.373,47.373,346,54,346" stroke="gold"/>

</svg>

<svg viewBox="40 220 28 140" >
  <desc>The long path</desc>
      <path d="M54,225 C60.627,225 66,230.373 66,237" stroke="red"/> 
      <path d="M66,237 L66,356" stroke="blue" />
      <path d="M66,356 L42,356" stroke="green" />  
      <path d="M42,356 L42,237" stroke="blue"/>
      <path d="M42,237 C42,230.373 47.373,225 54,225;" stroke="gold"/>

</svg>