annotate rust/README.rst @ 38297:9f499d28efb4

hgweb: pass a sysstr to low-level _start_response method This fixes a regression in Python 3 support introduced in 7de7bd407251 on the stable branch. We're so early in do_hgweb that I don't see any especially better choices than this. Differential Revision: https://phab.mercurial-scm.org/D3726
author Augie Fackler <augie@google.com>
date Tue, 12 Jun 2018 20:42:42 -0400
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children 8a3b045d9086
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1 ===================
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2 Mercurial Rust Code
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3 ===================
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4
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5 This directory contains various Rust code for the Mercurial project.
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6
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7 The top-level ``Cargo.toml`` file defines a workspace containing
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8 all primary Mercurial crates.
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9
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10 Building
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11 ========
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12
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13 To build the Rust components::
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14
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15 $ cargo build
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16
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17 If you prefer a non-debug / release configuration::
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18
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19 $ cargo build --release
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20
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21 Features
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22 --------
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23
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24 The following Cargo features are available:
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25
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26 localdev (default)
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27 Produce files that work with an in-source-tree build.
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28
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29 In this mode, the build finds and uses a ``python2.7`` binary from
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30 ``PATH``. The ``hg`` binary assumes it runs from ``rust/target/<target>hg``
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31 and it finds Mercurial files at ``dirname($0)/../../../``.
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32
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33 Build Mechanism
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34 ---------------
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35
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36 The produced ``hg`` binary is *bound* to a CPython installation. The
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37 binary links against and loads a CPython library that is discovered
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38 at build time (by a ``build.rs`` Cargo build script). The Python
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39 standard library defined by this CPython installation is also used.
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40
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41 Finding the appropriate CPython installation to use is done by
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42 the ``python27-sys`` crate's ``build.rs``. Its search order is::
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43
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44 1. ``PYTHON_SYS_EXECUTABLE`` environment variable.
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45 2. ``python`` executable on ``PATH``
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46 3. ``python2`` executable on ``PATH``
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47 4. ``python2.7`` executable on ``PATH``
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48
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49 Additional verification of the found Python will be performed by our
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50 ``build.rs`` to ensure it meets Mercurial's requirements.
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51
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52 Details about the build-time configured Python are built into the
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53 produced ``hg`` binary. This means that a built ``hg`` binary is only
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54 suitable for a specific, well-defined role. These roles are controlled
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55 by Cargo features (see above).
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56
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57 Running
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58 =======
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59
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60 The ``hgcli`` crate produces an ``hg`` binary. You can run this binary
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61 via ``cargo run``::
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62
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63 $ cargo run --manifest-path hgcli/Cargo.toml
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64
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65 Or directly::
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66
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67 $ target/debug/hg
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68 $ target/release/hg
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69
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70 You can also run the test harness with this binary::
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71
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72 $ ./run-tests.py --with-hg ../rust/target/debug/hg
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73
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74 .. note::
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75
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76 Integration with the test harness is still preliminary. Remember to
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77 ``cargo build`` after changes because the test harness doesn't yet
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78 automatically build Rust code.