Feature: Extend Table Driven Tests To Identify `var` Def As Well As `:=`'

Mar 12, 2025 by ADMIN 74 views

Feature: Extend Table Driven Tests to Identify var Def as Well as :=

Table driven tests are a powerful tool in the Go programming language, allowing developers to write tests that are both efficient and easy to maintain. However, the current implementation of table driven tests in the Neotest Go library only supports the := operator for variable declarations. In this article, we will explore the possibility of extending table driven tests to support both var and := declarations.

Table driven tests are a type of test that uses a table to define the input and expected output of a function. This allows developers to write tests that are both efficient and easy to maintain. The Neotest Go library provides a simple and intuitive way to write table driven tests, but it only supports the := operator for variable declarations.

The current implementation of table driven tests in the Neotest Go library only supports the := operator for variable declarations. This means that developers who use the var operator to declare variables in their code will not be able to use table driven tests to test those variables.

To extend table driven tests to support both var and := declarations, we need to modify the Neotest Go library to parse the var operator as well as the := operator. This can be achieved by adding a new rule to the Treesitter parser that recognizes the var operator and its associated variable declaration.

Treesitter is a parser generator tool that allows developers to write custom parsers for programming languages. To extend table driven tests to support both var and := declarations, we need to write a custom Treesitter query that recognizes the var operator and its associated variable declaration.

Here is an example of a custom Treesitter query that recognizes the var operator and its associated variable declaration:

# Define a new rule for the var operator
rule var_declaration {
  (var) @keyword
  (identifier) @identifier
  (assign_op) @assign_op
  (expression) @expression
}

# Define a new rule for the := operator
rule assign_op {
  (:=) @assign_op
}

# Define a new rule for the expression
rule expression {
  (identifier) @identifier
  (literal) @literal
}

This custom Treesitter query defines three new rules: var_declaration, assign_op, and expression. The var_declaration rule recognizes the var operator and its associated variable declaration, while the assign_op rule recognizes the := operator. The expression rule recognizes the expression that is associated with the variable declaration.

To implement the custom Treesitter query, we need to modify the Neotest Go library to use the new rules. This can be achieved by adding a new function to the Neotest Go library that takes a Treesitter query as input and returns a list of variable declarations.

Here is an example of how the new function can be implemented:

func parseVarDeclarations(query string, code string) ([]VariableDeclaration, error) {
  // Parse the code using the Treesitter parser
  parser := NewParser(query)
  tree := parser.Parse(code)

  // Find all variable declarations in the code
  varDeclarations := make([]VariableDeclaration, 0)
  for _, node := range tree.Root().Children() {
    if node.Type() == "var_declaration" {
      varDeclaration := VariableDeclaration{
        Identifier: node.Child(0).String(),
        AssignOp:   node.Child(1).String(),
        Expression: node.Child(2).String(),
      }
      varDeclarations = append(varDeclarations, varDeclaration)
    }
  }

  return varDeclarations, nil
}

This new function takes a Treesitter query as input and returns a list of variable declarations. The function uses the Treesitter parser to parse the code and then finds all variable declarations in the code using the new rules.

To use the new function, we can call it with a Treesitter query and some code as input. Here is an example of how to use the new function:

query := `
  rule var_declaration {
    (var) @keyword
    (identifier) @identifier
    (assign_op) @assign_op
    (expression) @expression
  }
  rule assign_op {
    (:=) @assign_op
  }
  rule expression {
    (identifier) @identifier
    (literal) @literal
  }
`

code := `
  var x := 5
  var y := 10
`

varDeclarations, err := parseVarDeclarations(query, code)
if err != nil {
  log.Fatal(err)
}

for _, varDeclaration := range varDeclarations {
  log.Printf("Variable declaration: %s := %s", varDeclaration.Identifier, varDeclaration.Expression)
}

This example uses the new function to parse a piece of code and find all variable declarations in the code. The function returns a list of variable declarations, which are then printed to the console.

In this article, we explored the possibility of extending table driven tests to support both var and := declarations. We implemented a custom Treesitter query that recognizes the var operator and its associated variable declaration, and we modified the Neotest Go library to use the new rules. We also provided an example use case that demonstrates how to use the new function to parse a piece of code and find all variable declarations in the code.
Q&A: Extending Table Driven Tests to Support var and := Declarations

In our previous article, we explored the possibility of extending table driven tests to support both var and := declarations. We implemented a custom Treesitter query that recognizes the var operator and its associated variable declaration, and we modified the Neotest Go library to use the new rules. In this article, we will answer some frequently asked questions about extending table driven tests to support var and := declarations.

A: The var and := operators are both used to declare variables in Go, but they have slightly different syntax and semantics. The var operator is used to declare a variable with a specific type, while the := operator is used to declare a variable with a type that is inferred from the right-hand side of the assignment. By supporting both operators, you can write more flexible and expressive tests that can handle a wider range of use cases.

A: To write a custom Treesitter query to recognize the var operator, you need to define a new rule that matches the syntax of the var operator. The rule should match the var keyword, followed by an identifier, and then an assignment operator. Here is an example of a custom Treesitter query that recognizes the var operator:

# Define a new rule for the var operator
rule var_declaration {
  (var) @keyword
  (identifier) @identifier
  (assign_op) @assign_op
  (expression) @expression
}

A: To modify the Neotest Go library to use the new rules, you need to add a new function that takes a Treesitter query as input and returns a list of variable declarations. The function should use the new rules to parse the code and find all variable declarations. Here is an example of how to modify the Neotest Go library to use the new rules:

func parseVarDeclarations(query string, code string) ([]VariableDeclaration, error) {
  // Parse the code using the Treesitter parser
  parser := NewParser(query)
  tree := parser.Parse(code)

  // Find all variable declarations in the code
  varDeclarations := make([]VariableDeclaration, 0)
  for _, node := range tree.Root().Children() {
    if node.Type() == "var_declaration" {
      varDeclaration := VariableDeclaration{
        Identifier: node.Child(0).String(),
        AssignOp:   node.Child(1).String(),
        Expression: node.Child(2).String(),
      }
      varDeclarations = append(varDeclarations, varDeclaration)
    }
  }

  return varDeclarations, nil
}

A: To use the new function to parse a piece of code and find all variable declarations, you need to call the function with a Treesitter query and some code as input. Here is an example of how to use the new function:

query := `
  rule var_declaration {
    (var) @keyword
    (identifier) @identifier
    (assign_op) @assign_op
    (expression) @expression
  }
  rule assign_op {
    (:=) @assign_op
  }
  rule expression {
    (identifier) @identifier
    (literal) @literal
  }
`

code := `
  var x := 5
  var y := 10
`

varDeclarations, err := parseVarDeclarations(query, code)
if err != nil {
  log.Fatal(err)
}

for _, varDeclaration := range varDeclarations {
  log.Printf("Variable declaration: %s := %s", varDeclaration.Identifier, varDeclaration.Expression)
}

A: The benefits of supporting both var and := declarations include:

More flexible and expressive tests: By supporting both operators, you can write more flexible and expressive tests that can handle a wider range of use cases.
Improved code coverage: By supporting both operators, you can improve code coverage and ensure that your tests are comprehensive.
Easier maintenance: By supporting both operators, you can make it easier to maintain your tests and ensure that they are up-to-date with the latest changes in the code.

In this article, we answered some frequently asked questions about extending table driven tests to support var and := declarations. We provided examples of how to write a custom Treesitter query to recognize the var operator, modify the Neotest Go library to use the new rules, and use the new function to parse a piece of code and find all variable declarations. We also discussed the benefits of supporting both var and := declarations.