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Fix spurious rebuilds of the script crate #7936

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merged 1 commit into from Oct 9, 2015

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@alexcrichton
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alexcrichton commented Oct 9, 2015

The script crate currently has a build script, and Cargo will consider all files
in the script crate as inputs to the build script as it otherwise doesn't know
what the input files are. This means that if any file in the
source tree of the script crate changes (or is created) then Cargo will think it
needs to re-run the build script and rebuild the crate.

The build script of the script crate is invoking python, and consequently Python
is generating some bytecode files in the source tree. On the second build of
Servo, Cargo will see these new files, think that something has changed, and
will re-run the build script of the script crate.

This change passes the -B flag to python to avoid generating these bytecode
files, which should avoid tampering with the source tree and appease Cargo by
ensuring that it doesn't get rebuilt.


As a helpful tip to if this comes up again, this was discovered by using the
changes in rust-lang/cargo@c447e9d plus the change in rust-lang/cargo#2044. Once
RUST_LOG was set to cargo::ops::cargo_rustc::fingerprint=info, the second
run of ./mach build printed out:

precalculated components have changed:
  1444364448.000000000s (/build/servo/components/script/dom/bindings/codegen/parser/WebIDL.pyc) !=
  1444364235.000000000s (/build/servo/components/script/document_loader.rs)

Which should help easily diagnose these kinds of problems in the future!

Review on Reviewable

The script crate currently has a build script, and Cargo will consider all files
in the script crate as inputs to the build script as it otherwise doesn't know
[what the input files are][cargo-1162]. This means that if any file in the
source tree of the script crate changes (or is created) then Cargo will think it
needs to re-run the build script and rebuild the crate.

[cargo-1162]: rust-lang/cargo#1162

The build script of the script crate is invoking python, and consequently Python
is generating some bytecode files in the source tree. On the second build of
Servo, Cargo will see these new files, think that something has changed, and
will re-run the build script of the script crate.

This change passes the `-B` flag to python to avoid generating these bytecode
files, which should avoid tampering with the source tree and appease Cargo by
ensuring that it doesn't get rebuilt.

---

As a helpful tip to if this comes up again, this was discovered by using the
changes in rust-lang/cargo@c447e9d plus the change in rust-lang/cargo#2044. Once
`RUST_LOG` was set to `cargo::ops::cargo_rustc::fingerprint=info`, the second
run of `./mach build` printed out:

```
precalculated components have changed:
  1444364448.000000000s (/build/servo/components/script/dom/bindings/codegen/parser/WebIDL.pyc) !=
  1444364235.000000000s (/build/servo/components/script/document_loader.rs)
```

Which should help easily diagnose these kinds of problems in the future!
@highfive
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highfive commented Oct 9, 2015

Thanks for the pull request, and welcome! The Servo team is excited to review your changes, and you should hear from @SimonSapin (or someone else) soon.

@glennw
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glennw commented Oct 9, 2015

👍 👏

@glennw
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glennw commented Oct 9, 2015

@bors-servo
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bors-servo commented Oct 9, 2015

📌 Commit e8eebc1 has been approved by glennw

@bors-servo
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bors-servo commented Oct 9, 2015

Testing commit e8eebc1 with merge 6321517...

bors-servo pushed a commit that referenced this pull request Oct 9, 2015
Fix spurious rebuilds of the script crate

The script crate currently has a build script, and Cargo will consider all files
in the script crate as inputs to the build script as it otherwise doesn't know
[what the input files are][cargo-1162]. This means that if any file in the
source tree of the script crate changes (or is created) then Cargo will think it
needs to re-run the build script and rebuild the crate.

[cargo-1162]: rust-lang/cargo#1162

The build script of the script crate is invoking python, and consequently Python
is generating some bytecode files in the source tree. On the second build of
Servo, Cargo will see these new files, think that something has changed, and
will re-run the build script of the script crate.

This change passes the `-B` flag to python to avoid generating these bytecode
files, which should avoid tampering with the source tree and appease Cargo by
ensuring that it doesn't get rebuilt.

---

As a helpful tip to if this comes up again, this was discovered by using the
changes in rust-lang/cargo@c447e9d plus the change in rust-lang/cargo#2044. Once
`RUST_LOG` was set to `cargo::ops::cargo_rustc::fingerprint=info`, the second
run of `./mach build` printed out:

```
precalculated components have changed:
  1444364448.000000000s (/build/servo/components/script/dom/bindings/codegen/parser/WebIDL.pyc) !=
  1444364235.000000000s (/build/servo/components/script/document_loader.rs)
```

Which should help easily diagnose these kinds of problems in the future!

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/7936)
<!-- Reviewable:end -->
@bors-servo
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bors-servo commented Oct 9, 2015

💔 Test failed - linux-dev

@jdm
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jdm commented Oct 9, 2015

@bors-servo
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bors-servo commented Oct 9, 2015

📌 Commit e8eebc1 has been approved by jdm

@metajack
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metajack commented Oct 9, 2015

Was this a regression? I seem to recall that we were using -B before. In any case, nice find Alex!

@frewsxcv
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frewsxcv commented Oct 9, 2015

Was this a regression?

447fbdc

@jdm
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jdm commented Oct 9, 2015

@alexcrichton
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alexcrichton commented Oct 9, 2015

Oh and I should also mention that this should still happen by default due to this gitignore rule but there's a bug in cargo which means that Cargo isn't picking this up.

@bors-servo
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bors-servo commented Oct 9, 2015

Testing commit e8eebc1 with merge cc54b85...

bors-servo pushed a commit that referenced this pull request Oct 9, 2015
Fix spurious rebuilds of the script crate

The script crate currently has a build script, and Cargo will consider all files
in the script crate as inputs to the build script as it otherwise doesn't know
[what the input files are][cargo-1162]. This means that if any file in the
source tree of the script crate changes (or is created) then Cargo will think it
needs to re-run the build script and rebuild the crate.

[cargo-1162]: rust-lang/cargo#1162

The build script of the script crate is invoking python, and consequently Python
is generating some bytecode files in the source tree. On the second build of
Servo, Cargo will see these new files, think that something has changed, and
will re-run the build script of the script crate.

This change passes the `-B` flag to python to avoid generating these bytecode
files, which should avoid tampering with the source tree and appease Cargo by
ensuring that it doesn't get rebuilt.

---

As a helpful tip to if this comes up again, this was discovered by using the
changes in rust-lang/cargo@c447e9d plus the change in rust-lang/cargo#2044. Once
`RUST_LOG` was set to `cargo::ops::cargo_rustc::fingerprint=info`, the second
run of `./mach build` printed out:

```
precalculated components have changed:
  1444364448.000000000s (/build/servo/components/script/dom/bindings/codegen/parser/WebIDL.pyc) !=
  1444364235.000000000s (/build/servo/components/script/document_loader.rs)
```

Which should help easily diagnose these kinds of problems in the future!

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/7936)
<!-- Reviewable:end -->
@bors-servo
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bors-servo commented Oct 9, 2015

💔 Test failed - linux-rel

@frewsxcv
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frewsxcv commented Oct 9, 2015

@bors-servo
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bors-servo commented Oct 9, 2015

Testing commit e8eebc1 with merge bc54440...

bors-servo pushed a commit that referenced this pull request Oct 9, 2015
Fix spurious rebuilds of the script crate

The script crate currently has a build script, and Cargo will consider all files
in the script crate as inputs to the build script as it otherwise doesn't know
[what the input files are][cargo-1162]. This means that if any file in the
source tree of the script crate changes (or is created) then Cargo will think it
needs to re-run the build script and rebuild the crate.

[cargo-1162]: rust-lang/cargo#1162

The build script of the script crate is invoking python, and consequently Python
is generating some bytecode files in the source tree. On the second build of
Servo, Cargo will see these new files, think that something has changed, and
will re-run the build script of the script crate.

This change passes the `-B` flag to python to avoid generating these bytecode
files, which should avoid tampering with the source tree and appease Cargo by
ensuring that it doesn't get rebuilt.

---

As a helpful tip to if this comes up again, this was discovered by using the
changes in rust-lang/cargo@c447e9d plus the change in rust-lang/cargo#2044. Once
`RUST_LOG` was set to `cargo::ops::cargo_rustc::fingerprint=info`, the second
run of `./mach build` printed out:

```
precalculated components have changed:
  1444364448.000000000s (/build/servo/components/script/dom/bindings/codegen/parser/WebIDL.pyc) !=
  1444364235.000000000s (/build/servo/components/script/document_loader.rs)
```

Which should help easily diagnose these kinds of problems in the future!

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/7936)
<!-- Reviewable:end -->
@highfive highfive removed the S-tests-failed label Oct 9, 2015
@bors-servo
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bors-servo commented Oct 9, 2015

@bors-servo bors-servo merged commit e8eebc1 into servo:master Oct 9, 2015
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@alexcrichton alexcrichton deleted the alexcrichton:script-rebuild branch Oct 15, 2015
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