代码管理:生成带有各种规则的细微变化的源文件

问题描述

我有一个声明性语言的源文件(实际上是twolc)，我需要写很多变种:规范版本和许多非规范版本，每个版本都有一个或多个不同于规范的版本.例如，说规范文件具有三个规则:

I have a source file in a declarative language (twolc, actually) that I need to write many variations on: a normative version and many non-normative versions, each with one or more variations from the norm. For example, say the normative file has three rules:

Rule A:
    Do something A-ish

Rule B:
    Do something B-ish

Rule C:
    Do something C-ish

那么一个变体可能具有与A和C的规范完全相同的规则，但是对于B的规则却不同，我将其称为B-1:

Then one variation might have the exact same rules as the norm for A and C, but a different rule for B, which I will call B-1:

Rule A:
    Do something A-ish

Rule B-1:
    Do something B-ish, but with a flourish

Rule C:
    Do something C-ish

想象一下，您在许多不同的规则上有许多不同的细微变化，而您有我的情况.我担心的问题是代码的可维护性.如果以后我决定需要以某种方式重构Rule A，那么我将有50多个文件需要手工编辑完全相同的规则.

Imagine that you have many different subtle variations on many different rules, and you have my situation. The problem I am worried about is code maintainability. If, later on, I decide that Rule A needs to be refactored somehow, then I will have 50+ files that need to have the exact same rule edited by hand.

我的想法是为每个规则使用单独的文件，并使用cat:cat A.twolc B.twolc C.twolc > norm.twolc，cat A.twolc B-1.twolc C.twolc > not-norm.twolc等将它们连接为变体.

My idea is to have separate files for each rule and concatenate them into variations using cat: cat A.twolc B.twolc C.twolc > norm.twolc, cat A.twolc B-1.twolc C.twolc > not-norm.twolc, etc.

是否有设计用于解决此类问题的工具?有没有比我想到的方法更好的方法?我提出的解决方案是否有我应该注意的弱点?

Are there any tools designed to manage this kind of problem? Is there a better approach than the one I have in mind? Does my proposed solution have weaknesses I should watch out for?

推荐答案

添加了makefile标记后，这是基于GNU-make的(仅Gnu make)解决方案:

As you added the makefile tag, here is a GNU-make-based (and Gnu make only) solution:

# Edit this
RULES       := A B B-1 C
VARIATIONS  := norm not-norm
norm-rules  := A B C
not-norm-rules  := A B-1 C
# Do not edit below this line

VARIATIONSTWOLC := $(patsubst %,%.twolc,$(VARIATIONS))

all: $(VARIATIONSTWOLC)

define GEN_rules
$(1).twolc: $$(patsubst %,%.twolc,$$($(1)-rules))
    cat $$^ > $$@
endef
$(foreach v,$(VARIATIONS),$(eval $(call GEN_rules,$(v))))

clean:
    rm -f $(VARIATIONSTWOLC)

patsubst很简单. foreach-eval-call有点棘手.长话短说:它遍历所有变体(foreach).对于每个变体v，通过将$(1)替换为$(v)(当前变体)并将$$替换为$，它会扩展(call)GEN_rules.然后，将每个扩展结果实例化(eval)作为正常的生成规则.例如:对于v=norm，GEN_rules扩展产生:

patsubst is straightforward. The foreach-eval-call is a bit more tricky. Long story short: it loops over all variations (foreach). For each variation v, it expands (call) GEN_rules by replacing $(1) by $(v) (the current variation) and $$ by $. Each expansion result is then instantiated (eval) as a normal make rule. Example: for v=norm, the GEN_rules expansion produces:

norm.twolc: $(patsubst %,%.twolc,$(norm-rules))
    cat $^ > $@

依次扩展为(逐步):

第1步:

norm.twolc: $(patsubst %,%.twolc,A B C)
    cat $^ > $@

第二步:

norm.twolc: A.twolc B.twolc C.twolc
    cat $^ > $@

第3步:

norm.twolc: A.twolc B.twolc C.twolc
    cat A.twolc B.twolc C.twolc > norm.twolc

执行所需的操作:如果norm.twolc不存在，或者A.twolc，B.twolc，C.twolc中的任何一个比norm.twolc更新，则执行配方.

which does what you want: if norm.twolc does not exist or if any of A.twolc, B.twolc, C.twolc is more recent than norm.twolc, the recipe is executed.

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