How bazel genrule srcs works under the hood - bazel

Question

Well, I'm trying to figure out how srcs works for genrule, I have the following:
genrule(
name = "flutter_build_android",
srcs = [
"//:genfiles"
],
outs = ["android/mobile.apk"],
cmd_bash = "ls -ltr && flutter build apk > $#",
tags = ["local"]
)
//:genfiles is a filegroup using glob:
filegroup(
name = "genfiles",
srcs = glob(["lib/**","assets/**", "pubspec.yaml"])
)
When executing my genrule what I expect is only files under ://genfiles label should be returned, but it is returning all folders under my root project:

Answer 1

What's happening is that the genrule is tagged with local, and local means
precludes the action or test from being remotely cached, remotely executed, or run inside the sandbox
https://bazel.build/reference/be/common-definitions#common.tags
Sandboxing is what prevents an action from seeing files that aren't declared as dependencies (i.e. in srcs here). Without the sandbox, the action sees everything.
$ tree
.
├── BUILD
├── file1
├── file2
├── file3
└── WORKSPACE
0 directories, 5 files
$ cat BUILD
genrule(
name = "gen_foo",
outs = ["foo"],
srcs = ["file1"],
cmd = "echo ----- ; ls ; echo ----- ; wc -l $< > $#",
# tags = ["local"],
)
$ bazel build foo
INFO: Analyzed target //:foo (5 packages loaded, 9 targets configured).
INFO: Found 1 target...
INFO: From Executing genrule //:gen_foo:
-----
bazel-out
external
file1
-----
Target //:foo up-to-date:
bazel-bin/foo
INFO: Elapsed time: 0.379s, Critical Path: 0.02s
INFO: 2 processes: 1 internal, 1 linux-sandbox.
INFO: Build completed successfully, 2 total actions
# edit BUILD to restore the local tag
$ cat BUILD
genrule(
name = "gen_foo",
outs = ["foo"],
srcs = ["file1"],
cmd = "echo ----- ; ls ; echo ----- ; wc -l $< > $#",
tags = ["local"],
)
$ bazel build foo
INFO: Analyzed target //:foo (5 packages loaded, 9 targets configured).
INFO: Found 1 target...
INFO: From Executing genrule //:gen_foo:
-----
BUILD
WORKSPACE
bazel-out
external
file1
file2
file3
local-spawn-runner.8714966150718292736
-----
Target //:foo up-to-date:
bazel-bin/foo
INFO: Elapsed time: 0.350s, Critical Path: 0.02s
INFO: 2 processes: 1 internal, 1 local.
INFO: Build completed successfully, 2 total actions