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88 lines
3.1 KiB
Python
88 lines
3.1 KiB
Python
#! /usr/bin/env python
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"""
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Multiple tasks can modify the same file(s)
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"""
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def configure(conf):
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pass
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def build(bld):
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bld.env.A = 'test 1'
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bld.env.B = 'test 2'
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bld.env.C = 'test 3'
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# recommended approach: just chain the commands/compilers/scripts
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# (the "rule" parameter is a tuple of strings)
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bld(
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rule=("echo '${A}' > ${TGT}", "echo '${B}' >> ${TGT}", "echo '${B}' >> ${TGT}"),
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target='bar.txt',
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name='bar',
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cls_keyword=lambda _: "single_chain",
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)
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# When tasks and targets are independent (update the same file "foo.txt"):
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#
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# 1. the initial task must depends on anything that can cause a rebuild, for example "cls_vars=['A', 'B', 'C']"
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# 2. the order must be described strictly, for example: "after='update_foo1'"
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# 3. "features='update_source'" is required to avoid rebuilds when the same input file is set: "source='foo.txt'"
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bld(rule="echo '${A}' > ${TGT}", target='foo.txt', name='create_foo', cls_keyword=lambda _: "foo1", vars=['A', 'B', 'C'])
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bld(rule="echo '${B}' >> ${SRC}", source='foo.txt', name='update_foo1', cls_keyword=lambda _:"foo2", after=['create_foo'], features='update_source')
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bld(rule="echo '${C}' >> ${SRC}", source='foo.txt', name='update_foo2', cls_keyword=lambda _:"foo3", after=['update_foo1'], features='update_source')
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# can be tested using
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# rule="if [ $$(( $$RANDOM %% 2)) -eq 0 ]; then exit 1; fi; echo '${C}' >> ${SRC}"
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# --------------------------------------------------------------------------------------------
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from waflib.TaskGen import feature, after_method
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from waflib import Task
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def recompute_post_run(self):
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# In general, inputs are assumed to be unchanged between builds
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# which is also a safeguard when developers modify source files while building
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#
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# For the case above, the caches should be cleared for specific tasks
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if getattr(self, 'busy_recompute', None):
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# simple lock required due to traversing the entire task tree below
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return
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self.busy_recompute = True
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# traverse the task tree: other tasks that use the same inputs need their caches cleared too
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# this traversal (and the lock) are unnessary if a file is updated only once
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for idx, group in enumerate(self.generator.bld.groups):
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if idx > self.generator.bld.current_group:
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# ignore downstream tasks
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break
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for tg in group:
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for tsk in tg.tasks:
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if not tsk.hasrun:
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# ignore downstream tasks
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continue
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for in_node in self.inputs:
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if in_node in tsk.inputs:
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# assume that "recompute_post_run" is set on those tasks too
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tsk.post_run()
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break
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delattr(self, 'busy_recompute')
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# delete caches before recomputing
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for node in self.inputs:
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del node.ctx.cache_sig[node]
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del self.cache_sig
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# this assumes that the method post_run can be called more than once with similar effects
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return Task.Task.post_run(self)
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@feature('update_source')
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@after_method('process_source', 'process_rule')
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def update_source(self):
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# assume that all task objects are created at this point
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# more "after_method" annotations might be necessary, depending
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# on the project
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for task in self.tasks:
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task.__class__.post_run = recompute_post_run
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