fix ast expression tests for null expressions

[kesor]

Pull Request Name

Fix a TypeError exception for null expressions in the AST.

Description

While linting my application, exceptions about the AST are raised in some components:

TypeError: Cannot read properties of null (reading 'type') Occurred while linting /app/src/components/TestComponent.vue:47 Rule: "vue/attributes-order"
    at isArrayExpression (/app/node_modules/eslint-plugin-tailwindcss/lib/util/ast.js:99:92)
    at isVueValidAttributeValue (/app/node_modules/eslint-plugin-tailwindcss/lib/util/ast.js:121:10)
    at Object.isValidVueAttribute (/app/node_modules/eslint-plugin-tailwindcss/lib/util/ast.js:184:8)

Apparently the VExpressionContainer can pass all the checks, but the value for expression is null. This modification makes sure it is not treated as an object that can be passed onward.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Linting fails on some components in our big application, this change fixes the thrown exception.

Test Configuration:

• OS + version: Debian 11
• NPM version: 10.8.1
• Node version: 22.3.0

[francoismassart]

@kesor could you provide an example of the failing AST parsing ?

Thank you

[kesor]

This is a bit hard to debug, but if I am not mistaken it would be this Vue.js element --

          <td
            class="text-end"
            :class="(marketValue ?? 0) < (totalCost ?? 0) ? 'text-danger' : 'text-success'"
          >
            {{ marketValue?.toFixed(2) }}
          </td>

Some debug logging that I patched the ast.js to print out include --

<ref *2> {                                                                                                                                                                                                                            
  type: 'VAttribute',                                                                                                                                                                                                                 
  range: [ 3690, 3769 ],                                                                                                                                                                                                              
  loc: { start: { line: 103, column: 12 }, end: { line: 103, column: 91 } },                                                                                                                                                          
  parent: <ref *1> {                                                                                                                                                                                                                  
    type: 'VStartTag',                                                                                                                                                                                                                
    range: [ 3645, 3781 ],                                                                                                                                                                                                            
    loc: { start: [Object], end: [Object] },                                                                                                                                                                                          
    parent: {                                                                                                                                                                                                                         
      type: 'VElement',                                                                                                                                                                                                               
      range: [Array],                                                                                                                                                                                                                 
      loc: [Object],                                                                                                                                                                                                                  
      parent: [Object],                                                                                                                                                                                                               
      name: 'td',                                                                                                                                                                                                                     
      rawName: 'td',                                                                                                                                                                                                                  
      namespace: 'http://www.w3.org/1999/xhtml',                                                                                                                                                                                      
      startTag: [Circular *1],                                                                                                                                                                                                        
      children: [Array],                                                                                                                                                                                                              
      endTag: [Object],                                                                                                                                                                                                               
      variables: []                                                                                                                                                                                                                   
    },                                                                                                                                                                                                                                
    selfClosing: false,                                                                                                                                                                                                               
    attributes: [ [Object], [Circular *2] ]                                                                                                                                                                                           
  },                          
  directive: true,                                       
  key: <ref *3> {   
    type: 'VDirectiveKey',                               
    range: [ 3690, 3696 ],                                                                                         
    loc: { start: [Object], end: [Object] },                                                                       
    parent: [Circular *2],  
    name: {                                                                                                                                                                                                                           
      type: 'VIdentifier',                                                                                                                                                                                                            
      parent: [Circular *3],                                                                                                                                                                                                          
      range: [Array],                                                                                                                                                                                                                 
      loc: [Object],                         
      name: 'bind',                                                                                                                                                                                                                   
      rawName: ':'                                                                                                                                                                                                                    
    },                                                                                                             
    argument: {                                                                                                    
      type: 'VIdentifier',                                                                                         
      parent: [Circular *3],                             
      range: [Array],
      loc: [Object],
      name: 'class',
      rawName: 'class'
    },
    modifiers: []
  },
  value: {
    type: 'VExpressionContainer',
    range: [ 3697, 3769 ],
    loc: { start: [Object], end: [Object] },
    parent: [Circular *2],
    expression: null,
    references: []
  }
}

[francoismassart]

Thanks, I was able to reproduce the BUG then to confirm the fix is working as expected.