Linking the vertex shader 2 times works, but not linking the vertex and the fragment shader

Question

it has been days since I'm trying to debug my project that I recently updated from LWJGL2 to LWJGL3. I found some issues, but still it wasn't working so I made a minimal project, like really minimal and compared it to a working project I found online. I came to a point where the 2 projects were absolutely the same, excepted that in the working project I create the vertex shader 2 times and link the 2 in the program, and on the other one I'm linking the correct ones, they both compile but nothing renders.

Here is the Shader class:

private int vertexID, fragmentID, programID;
    
    public Shader(String vertexPath, String fragmentPath) {
        vertexID = loadShader(vertexPath,GL20.GL_VERTEX_SHADER);
        fragmentID = loadShader(fragmentPath,GL20.GL_FRAGMENT_SHADER); //Not working
        //fragmentID = loadShader(vertexPath,GL20.GL_VERTEX_SHADER); // Working ?????
        programID = GL20.glCreateProgram();

        GL20.glAttachShader(programID, vertexID);
        GL20.glAttachShader(programID, fragmentID);

        GL20.glLinkProgram(programID);
        GL20.glValidateProgram(programID);
    }

    private int loadShader(String file,int type) {
        StringBuilder shaderSource = new StringBuilder();
        try{
            BufferedReader reader = new BufferedReader(new FileReader(file));
            String line;
            while((line = reader.readLine())!=null){
                shaderSource.append(line).append("//\n");
            }
            reader.close();
        }catch(IOException e){
            e.printStackTrace();
            System.exit(-1);
        }
        int shaderID = GL20.glCreateShader(type);
        GL20.glShaderSource(shaderID, shaderSource);
        GL20.glCompileShader(shaderID);
        if(GL20.glGetShaderi(shaderID, GL20.GL_COMPILE_STATUS )== GL11.GL_FALSE){
            System.out.println(GL20.glGetShaderInfoLog(shaderID, 500));
            System.err.println("Could not compile shader!");
            System.exit(-1);
        }
        return shaderID;
    }

Here is the fragment shader:

#version 460 core

in vec3 color;

out vec4 outColor;

void main() {
    outColor = vec4(color, 1.0);
}

And the vertex shader:

#version 460 core

in vec3 position;

out vec3 color;

void main() {
    color = vec3(1,1,1);
}

And here is the line to create the Shader class called right after creating the display:

    shader = new Shader("src/mainVertex", "src/mainFragment");

I don't what is going on, maybe the problem is the fragment shader, maybe the reader. Thanks for your help.

Answer 1

as @Rabbid76 said, I was missing gl_Position in the vertex shader, but still I don't know why linking the vertex shader two times was working.