evmar
Path expansion in builds doesn't take take build variables in context
In Ninja, the below refers to the file foo.3.
build foo.$bar: baz ...
bar = 3
In n2 this doesn't. n2 aggressively expands variables while parsing, which is to say that in the above it never even generates intermediate data like the parse of foo.$bar, but rather expands $bar right as it sees it and then interns the path, and even reuses that buffer to parse/canonicalize the next path.
This is fixable but I'm kinda hesitant. To implement the Ninja behavior we'd instead need to build up an array of all the paths and then expand them once we've parsed through the variables. (Edit: another possibly costlier idea, we could skip forward to the variables, parse them, then go back and parse the paths again.)
The fact that builds seem to currently work suggests that maybe existing projects don't depend on this?
For what it's worth, this was one of the two issues I faced in our build when trying to switch over to n2 from ninja. Our build generator would define things like $builddir at the top of build.ninja, and then in individual build steps, it would use variables that made use of them, eg out_dir = $builddir/some/path.
Dang, that's a pretty strong argument that we ought to fix this. Unfortunately it will likely end up fairly costly. :( n2 is very aggressive about trying to do work incrementally to avoid needing to buffer stuff while parsing...
Might be worth waiting around to see if anyone else hits this - it was fairly easy to work around in our case, and we may be an outlier. Doing a couple of string replacements in the build generator does seem to make more sense that pushing the work to build time.
For what it's worth, this was one of the two issues I faced in our build when trying to switch over to n2 from ninja. Our build generator would define things like $builddir at the top of build.ninja, and then in individual build steps, it would use variables that made use of them, eg out_dir = $builddir/some/path.
Rereading this, I think this ought to be something that currently does work with n2. The specific issue here is instead about how in some (rare) cases Ninja variable expansion refers to a variable that it defined textually below where it's referenced, while n2 expands things roughly top-down. So I think that doesn't describe what you encountered.
I might be missing something. Here's an example:
builddir = /home/dae/Local/build/anki
runner = $builddir/rust/release/runner
rule CargoBuild
command = $runner run cargo build $release_arg $target_arg --locked $extra_args
restat = 1
hide_success = 1
hide_last_line = 0
build | $builddir/rust/debug/configure: CargoBuild | .cargo/config.toml Cargo.lock build/configure/Cargo.toml build/configure/src/aqt.rs build/configure/src/bundle.rs build/configure/src/main.rs build/configure/src/platform.rs build/configure/src/pylib.rs build/configure/src/python.rs build/configure/src/rust.rs build/configure/src/web.rs build/ninja_gen/Cargo.toml build/ninja_gen/src/action.rs build/ninja_gen/src/archives.rs build/ninja_gen/src/build.rs build/ninja_gen/src/cargo.rs build/ninja_gen/src/command.rs build/ninja_gen/src/configure.rs build/ninja_gen/src/copy.rs build/ninja_gen/src/git.rs build/ninja_gen/src/hash.rs build/ninja_gen/src/input.rs build/ninja_gen/src/lib.rs build/ninja_gen/src/node.rs build/ninja_gen/src/protobuf.rs build/ninja_gen/src/python.rs build/ninja_gen/src/render.rs build/ninja_gen/src/rsync.rs build/ninja_gen/src/sass.rs build/runner/Cargo.toml build/runner/build.rs build/runner/src/archive.rs build/runner/src/build.rs build/runner/src/bundle/artifacts.rs build/runner/src/bundle/binary.rs build/runner/src/bundle/folder.rs build/runner/src/bundle/mod.rs build/runner/src/main.rs build/runner/src/paths.rs build/runner/src/pyenv.rs build/runner/src/rsync.rs build/runner/src/run.rs build/runner/src/yarn.rs rust-toolchain.toml
configure = $builddir/rust/debug/configure
description = build:configure_bin
extra_args = -p configure
release_arg =
target_arg =
rule ConfigureBuild
command = $runner run $cmd
restat = 1
generator = 1
hide_success = 1
hide_last_line = 0
build | $builddir/build.ninja: ConfigureBuild | $builddir/env $builddir/rust/debug/configure .git .version
cmd = $builddir/rust/debug/configure
description = build:configure
This fails with:
failed: build:configure
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: DidNotExecute { cmdline: "/rust/debug/configure", source: Os { code: 2, kind: NotFound, message: "No such file or directory" } }', build/runner/src/run.rs:86:30
