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612cd01743
This change adds an option to skip the API checks during a build. This can be done by adding the trailer `Keyman-Api-Check: skip` to the PR description. Fixes: #10454 Test-bot: skip Keyman-Api-Check: skip
147 lines
5.1 KiB
Markdown
147 lines
5.1 KiB
Markdown
# Keyman Core API verification
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After the GHA Debian package build we verify that the API didn't change
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without being documented in `linux/debian/libkeymancore.symbols`.
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[Debian policy](https://www.debian.org/doc/debian-policy/ch-sharedlibs#run-time-shared-libraries)
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mandates that the API version of a shared library gets changed when the shared
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library ABI changes in a way that could break binaries linked against
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older versions of the shared library. This means that the API version should
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change any time an interface is removed from the shared library or the
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signature of an interface changes.
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## Format of the `libkeymancore.symbols` file
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The format of the file is documented in the
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[deb-src-symbols man page](https://www.man7.org/linux/man-pages/man5/deb-src-symbols.5.html).
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The majority of the lines are API method names followed by the
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Keyman version where that symbol got introduced. Note that the lines
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have to begin with a space character.
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Example:
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```text
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km_core_state_actions_get@Base 17.0.197
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```
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## What to do when the API verification check fails
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If you change the API but forget to update the `.symbols` file or the
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API version number, the API verfication step in the GitHub Action
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Ubuntu packaging workflow will fail.
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There are different reasons why the API verification step can fail:
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### You added a new API method
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If you added a new API method to Keyman Core but didn't update the
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`libkeymancore.symbols` file, `dpkg-gensymbols` will output a diff
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between the old and the new API. You can edit `libkeymancore.symbols`
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and add the missing line(s) that the diff shows. Note that the version
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number should be the Keyman version that is current when the PR gets
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merged.
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### `dpkg-gensymbols` complains about C++ symbols
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Unfortunately, `dpkg-gensymbols` which processes `libkeymancore.symbols` doesn't
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work particularly well with C++, so it might flag some C++ symbols even though
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they aren't part of the API. This happens particularly with C++ template
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instantiations.
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To work around this, we list the C++ symbols as `optional` that get flagged:
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```text
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(c++|optional)"typeinfo name for std::codecvt_utf8_utf16<char16_t, 1114111ul, (std::codecvt_mode)0>@Base" 17.0.244
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```
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`dpkg-gensymbols` will report the mangled C++ name in the diff, e.g.
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```text
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+ _ZTSSt18codecvt_utf8_utf16IDsLm1114111ELSt12codecvt_mode0EE@Base 17.0.244
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```
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but for `libkeymancore.symbols` we need the demangled name. This can be
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retrieved by running:
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```bash
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echo "_ZTSSt18codecvt_utf8_utf16IDsLm1114111ELSt12codecvt_mode0EE@Base" | c++filt
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```
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which will output the demangled name:
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```text
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typeinfo name for std::codecvt_utf8_utf16<char16_t, 1114111ul, (std::codecvt_mode)0>@Base
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```
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Add the full output in quotes to `libkeymancore.symbols`, preceded by
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`(c++|optional)` and followed by the version number.
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Note that here again a space at the beginning of the line is required.
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### You added an old Keyman version number
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The API verification will also fail if you add a new line to the
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`libkeymancore.symbols` file but don't update the version number at the
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end of the line to the current Keyman version. In this case simply
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modify the version number to the value you find in `VERSION.md`.
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### You forgot to update the API version number in the `.symbols` file
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When you remove or modify existing lines in the `libkeymancore.symbols`
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file, you'll have to update the API version number at the top of the file
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(the "1" in `libkeymancore.so.1`).
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### You forgot to update `CORE_API_VERSION.md`
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When you remove or modify API methods, you'll also have to update
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the API version number in `CORE_API_VERSION.md`. If the API version
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numbers in `CORE_API_VERSION.md` and in `libkeymancore.symbols` don't
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match the API verification will fail.
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## Skipping the API check
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Sometimes we have a PR that intentionally does not change the API version
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number. To skip the API checks in this case, the trailer
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```text
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Keyman-Api-Check: skip
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```
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can be added to the PR description.
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## How this works
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`.github/workflows/api-verification.yml` contains a `Verify API` step
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which will call `linux/scripts/deb-packaging.sh` with the `verify`
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parameter. Before calling the script it will download and extract
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the binary package artifacts.
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`deb-packaging.sh` will call `dpkg-gensymbols` which will compare the
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previous API with the current one. Then the script will run some
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additional verifications:
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- checks that the version number of inserted lines matches `VERSION.md`
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- checks that the API version number in `libkeymancore.symbols` got
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updated if necessary
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- checks that `CORE_API_VERSION.md` got updated if necessary
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`dpkg-gensymbols` will generate a new `symbols` file which the GHA
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verification will archive.
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Note that this `symbols` file can't be directly copied over
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`libkeymancore.symbols` since it removes the C++ regex lines from the template.
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### Running the API verification locally
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It's possible to run the API verification locally. To do that, download
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(or build) the binary package for at least one platform .
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Then run
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```bash
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cd linux
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dpkg -x libkeymancore*.deb /tmp
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mkdir -p debian/tmp/DEBIAN
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dpkg-gensymbols -v17.0.244 -plibkeymancore -e/tmp/usr/lib/x86_64-linux-gnu/libkeymancore.so* -c4
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```
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