抱歉标题模糊,但我真的不知道如何简洁地描述这个问题。
我创建了一种(或多或少)简单的特定于域的语言,我将使用它来指定适用于不同实体(通常是从网页提交的表单)的验证规则。我在这篇文章的底部包含了一个示例,说明该语言的外观。
我的问题是我不知道如何开始将这种语言解析为我可以使用的形式(我将使用 Python 进行解析)。我的目标是最终得到一个规则/过滤器列表(作为字符串,包括参数,例如'cocoa(99)'
),应该(按顺序)应用于每个对象/实体(也是一个字符串,例如'chocolate'
,'chocolate.lindt'
等)。
我不确定从什么技术开始,甚至不知道有什么技术可以解决这样的问题。你认为最好的方法是什么?我不是在寻找一个完整的解决方案,只是在正确的方向上进行一般性的推动。
谢谢。
语言示例文件:
# Comments start with the '#' character and last until the end of the line
# Indentation is significant (as in Python)
constant NINETY_NINE = 99 # Defines the constant `NINETY_NINE` to have the value `99`
*: # Applies to all data
isYummy # Everything must be yummy
chocolate: # To validate, say `validate("chocolate", object)`
sweet # chocolate must be sweet (but not necessarily chocolate.*)
lindt: # To validate, say `validate("chocolate.lindt", object)`
tasty # Applies only to chocolate.lindt (and not to chocolate.lindt.dark, for e.g.)
*: # Applies to all data under chocolate.lindt
smooth # Could also be written smooth()
creamy(1) # Level 1 creamy
dark: # dark has no special validation rules
extraDark:
melt # Filter that modifies the object being examined
c:bitter # Must be bitter, but only validated on client
s:cocoa(NINETY_NINE) # Must contain 99% cocoa, but only validated on server. Note constant
milk:
creamy(2) # Level 2 creamy, overrides creamy(1) of chocolate.lindt.* for chocolate.lindt.milk
creamy(3) # Overrides creamy(2) of previous line (all but the last specification of a given rule are ignored)
ruleset food: # To define a chunk of validation rules that can be expanded from the placeholder `food` (think macro)
caloriesWithin(10, 2000) # Unlimited parameters allowed
edible
leftovers: # Nested rules allowed in rulesets
stale
# Rulesets may be nested and/or include other rulesets in their definition
chocolate: # Previously defined groups can be re-opened and expanded later
ferrero:
hasHazelnut
cake:
tasty # Same rule used for different data (see chocolate.lindt)
isLie
ruleset food # Substitutes with rules defined for food; cake.leftovers must now be stale
pasta:
ruleset food # pasta.leftovers must also be stale
# Sample use (in JavaScript):
# var choc = {
# lindt: {
# cocoa: {
# percent: 67,
# mass: '27g'
# }
# }
# // Objects/groups that are ommitted (e.g. ferrro in this example) are not validated and raise no errors
# // Objects that are not defined in the validation rules do not raise any errors (e.g. cocoa in this example)
# };
# validate('chocolate', choc);
# `validate` called isYummy(choc), sweet(choc), isYummy(choc.lindt), smooth(choc.lindt), creamy(choc.lindt, 1), and tasty(choc.lindt) in that order
# `validate` returned an array of any validation errors that were found
# Order of rule validation for objects:
# The current object is initially the object passed in to the validation function (second argument).
# The entry point in the rule group hierarchy is given by the first argument to the validation function.
# 1. First all rules that apply to all objects (defined using '*') are applied to the current object,
# starting with the most global rules and ending with the most local ones.
# 2. Then all specific rules for the current object are applied.
# 3. Then a depth-first traversal of the current object is done, repeating steps 1 and 2 with each object found as the current object
# When two rules have equal priority, they are applied in the order they were defined in the file.
# No need to end on blank line