Validation Rules

OSC2 Studio provides real-time syntax and semantic validation to help you catch errors instantly while writing scenarios.

Syntax Validation

Syntax validation checks whether the code conforms to the OSC2 grammar specification, including:

• Correct indentation — Indentation errors cause parsing failures
• Keyword spelling — Whether keywords such as scenario, do, serial are correct
• Symbol matching — Whether brackets, colons, commas, and other symbols are complete
• Identifier format — Whether variable names and type names follow naming rules
• Import statements — Whether import paths are correctly formatted

Example syntax errors:

# Error: missing colon
scenario my_scenario
    do serial:         # Correct
        car.drive()

# Error: inconsistent indentation
scenario my_scenario:
    do serial:
    car.drive()         # Indentation error, should be 8 spaces

Semantic Validation

Semantic validation checks the logical correctness of the code — cases where syntax is correct but the semantics are problematic:

• Type checking — Whether variable types match (e.g., cannot assign a string to an int)
• Reference resolution — Whether variables, types, and actors have been declared
• Physical quantity checking — Whether units match (e.g., cannot assign kph to a length type)
• Scope checking — Whether a variable is referenced within a valid scope
• Duplicate declarations — Whether duplicate names exist in the same scope

Example semantic errors:

# Error: type mismatch
my_speed: speed = 10m        # 10m is a length, not a speed

# Error: undefined variable
car.drive() with:
    speed(undefined_var)     # undefined_var was not declared

# Error: unit mismatch
distance: length = 50kph     # kph is a speed unit, cannot be assigned to length

Constraint Validation

keep statements define conditions that must be satisfied during scenario execution:

keep(car.speed < 80kph)     # Hard constraint: vehicle speed must be below 80 km/h
keep(default x == 3)         # Default constraint: can be overridden
keep(x in [10..20])           # Range constraint: x is between 10 and 20

Constraint validation checks:

• Whether the constraint expression type is correct (e.g., both sides of speed < 80kph have consistent units)
• Whether the constraint is within a valid range
• Whether default constraints are correctly overridden

Coverage Checking

Use the cover statement to record test coverage:

extend my_scenario:
    cover(side, event: end, target: 10)

The validator checks whether the coverage target format is correct.

Validation Results

In the OSC2 Studio editor, validation results are displayed in the problems panel at the bottom:

• Red wavy lines — Syntax errors (must be fixed)
• Yellow wavy lines — Semantic warnings (recommended to fix)
• Green markers — Validation passed

Click an error marker to jump to the corresponding code location.