152 lines
3.5 KiB
Markdown
152 lines
3.5 KiB
Markdown
# Ninja File Canonicalizer
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Suppose we have a tool that generates a Ninja file from some other description (think Kati and makefiles), and during
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the testing we discovered a regression. Furthermore, suppose that the generated Ninja file is large (think millions of
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lines). And, the new Ninja file has build statements and rules in a slightly different order. As the tool generates the
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rule names, the real differences in the output of the `diff` command are drowned in noise. Enter Canoninja.
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Canoninja renames each Ninja rule to the hash of its contents. After that, we can just sort the build statements, and a
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simple `comm` command immediately reveal the essential difference between the files.
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## Example
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Consider the following makefile
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```makefile
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second :=
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first: foo
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foo:
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@echo foo
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second: bar
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bar:
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@echo bar
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```
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Depending on Kati version converting it to Ninja file will yield either:
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```
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$ cat /tmp/1.ninja
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# Generated by kati 06f2569b2d16628608c000a76e3d495a5a5528cb
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pool local_pool
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depth = 72
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build _kati_always_build_: phony
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build first: phony foo
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rule rule0
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description = build $out
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command = /bin/sh -c "echo foo"
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build foo: rule0
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build second: phony bar
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rule rule1
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description = build $out
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command = /bin/sh -c "echo bar"
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build bar: rule1
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default first
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```
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or
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```
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$ cat 2.ninja
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# Generated by kati 371194da71b3e191fea6f2ccceb7b061bd0de310
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pool local_pool
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depth = 72
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build _kati_always_build_: phony
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build second: phony bar
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rule rule0
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description = build $out
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command = /bin/sh -c "echo bar"
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build bar: rule0
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build first: phony foo
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rule rule1
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description = build $out
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command = /bin/sh -c "echo foo"
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build foo: rule1
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default first
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```
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This is a quirk in Kati, see https://github.com/google/kati/issues/238
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Trying to find out the difference between the targets even after sorting them isn't too helpful:
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```
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diff <(grep '^build' /tmp/1.ninja|sort) <(grep '^build' /tmp/2.ninja | sort)
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1c1
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< build bar: rule1
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---
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> build bar: rule0
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3c3
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< build foo: rule0
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---
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> build foo: rule1
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```
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However, running these files through `canoninja` yields
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```
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$ canoninja /tmp/1.ninja
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# Generated by kati 06f2569b2d16628608c000a76e3d495a5a5528cb
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pool local_pool
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depth = 72
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build _kati_always_build_: phony
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build first: phony foo
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rule R2f9981d3c152fc255370dc67028244f7bed72a03
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description = build $out
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command = /bin/sh -c "echo foo"
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build foo: R2f9981d3c152fc255370dc67028244f7bed72a03
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build second: phony bar
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rule R62640f3f9095cf2da5b9d9e2a82f746cc710c94c
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description = build $out
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command = /bin/sh -c "echo bar"
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build bar: R62640f3f9095cf2da5b9d9e2a82f746cc710c94c
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default first
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```
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and
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```
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~/go/bin/canoninja /tmp/2.ninja
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# Generated by kati 371194da71b3e191fea6f2ccceb7b061bd0de310
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pool local_pool
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depth = 72
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build _kati_always_build_: phony
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build second: phony bar
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rule R62640f3f9095cf2da5b9d9e2a82f746cc710c94c
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description = build $out
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command = /bin/sh -c "echo bar"
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build bar: R62640f3f9095cf2da5b9d9e2a82f746cc710c94c
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build first: phony foo
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rule R2f9981d3c152fc255370dc67028244f7bed72a03
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description = build $out
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command = /bin/sh -c "echo foo"
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build foo: R2f9981d3c152fc255370dc67028244f7bed72a03
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default first
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```
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and when we extract only build statements and sort them, we see that both Ninja files define the same graph:
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```shell
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$ diff <(~/go/bin/canoninja /tmp/1.ninja | grep '^build' | sort) \
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<(~/go/bin/canoninja /tmp/2.ninja | grep '^build' | sort)
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```
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# Todo
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* Optionally output only the build statements, optionally sorted
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* Handle continuation lines correctly
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