Live config override directory by tarek-y-ismail · Pull Request #4781 · canonical/mir

tarek-y-ismail · 2026-03-18T19:44:19Z

What's new?

TODO

How to test

 ./build/bin/miral-test --gtest_filter=TestOverrideConfigFile*

 ./build/bin/miral-test --gtest_filter=LiveConfigIniFile*

Checklist

Tests added and pass
Adequate documentation added
(optional) Added Screenshots or videos

tarek-y-ismail · 2026-03-18T19:47:52Z

I did not realize I wrote 1600+ lines of code. Might be wise to split this into a PR for the IniFile changes and another for the ConfigFile changes

Copilot

Pull request overview

This PR adds support for loading a base config file plus a companion override directory (<config>.d/*.conf) and applying those overrides as a single “transaction” to the live config store (handlers called once after aggregating all inputs), with reload-on-change support.

Changes:

Extend miral::live_config::IniFile with load_files() and implement multi-stream parsing/override semantics (including explicit array clearing).
Extend miral::ConfigFile with an OverrideLoader constructor and an inotify-based watcher for override directories and relevant symlink targets.
Add/expand tests for multi-stream INI behavior and override-directory loading/reloading; update demo server example to use the new multi-file loader.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
`src/miral/live_config_ini_file.cpp`	Implements multi-stream parsing, value provenance tracking, array clear semantics, and a `load_files()` entrypoint.
`include/miral/miral/live_config_ini_file.h`	Exposes `IniFile::load_files()` in the public API.
`src/miral/config_file.cpp`	Adds multi-file collection, override-directory discovery, and `OverrideWatcher` for reload-on-change.
`include/miral/miral/config_file.h`	Adds `OverrideLoader` type + constructor overload to support multi-file loading.
`tests/miral/live_config_ini_file.cpp`	Adds unit tests for override/aggregation semantics across multiple streams.
`tests/miral/config_file.cpp`	Adds a large suite of tests covering override dir loading/reloading and symlink cases.
`examples/mir_demo_server/server_example.cpp`	Switches demo server to load multi-file configs via `load_files()`.

Copilot · 2026-03-25T14:28:23Z

+      override_loader{load_config},
+      base_config_filename{base_config.filename().string()},
+      override_directory{base_config_filename + ".d"},
+      base_config_directory{config_directory(base_config.filename())},


base_config_directory is derived from config_directory(base_config.filename()), which drops any explicit parent path the caller provided (e.g. /tmp/foo.conf). That causes override watching to monitor $XDG_CONFIG_HOME/$HOME/.config instead of the supplied directory. Use config_directory(base_config) so explicit paths behave correctly.

Suggested change

base_config_directory{config_directory(base_config.filename())},

base_config_directory{config_directory(base_config)},

Copilot · 2026-03-25T14:28:24Z

 public:
    /// Loader functor is passed both the open stream and the actual path (for use in reporting problems)
    using Loader = std::function<void(std::istream& istream, std::filesystem::path const& path)>;
+    using OverrideLoader =
+        std::function<void(std::span<std::pair<std::unique_ptr<std::istream>, std::filesystem::path>>)>;



This header now uses std::span and std::pair/std::unique_ptr in the public API, but it doesn’t include <span> (and <utility> for std::pair). Relying on transitive includes makes the header non-self-contained and can break compilation for consumers.

Copilot · 2026-03-25T14:28:25Z

 #include <miral/test_server.h>
 #include <miral/config_file.h>

+#include <source_location>


#include <source_location> appears unused in this test file (no references found). If the build treats warnings as errors, this can fail CI; please remove it or use it.

Suggested change

#include <source_location>

Copilot · 2026-03-25T14:28:25Z

@@ -54,6 +56,7 @@ class ConfigFile
    };

    ConfigFile(MirRunner& runner, std::filesystem::path file, Mode mode, Loader load_config);
+    ConfigFile(MirRunner& runner, std::filesystem::path file, Mode mode, OverrideLoader load_config);
    ~ConfigFile();


Adding an overload that takes OverrideLoader makes call sites using generic lambdas (e.g. [](auto&... args){...}) ambiguous because such lambdas are callable with both (istream&, path) and (span<...>). Consider making the overload selection unambiguous (e.g. via a tag type, a differently-named constructor/factory, or documenting that callers should wrap lambdas in ConfigFile::Loader{...} / ConfigFile::OverrideLoader{...}).

tarek-y-ismail · 2026-03-25T14:28:39Z

Ok, splitting IniFile changes out improved things a bit. But ConfigFile tests are almost 1000 lines, so the PR is still big...

tarek-y-ismail · 2026-03-26T14:43:22Z

After a quick discussion with @Saviq, we're going to implement this without support for symlinks initially. That can come later.

`reloads_when_override_file_is_added`

config tests

- Test reload on override directory deletion at runtime - Test reload when a symlinked override file is added after startup and its target is modified - Test reload when a relative symlinked override file target is modified

base config directory

tarek-y-ismail self-assigned this Mar 18, 2026

tarek-y-ismail mentioned this pull request Mar 25, 2026

Live config ini file changes #4799

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1 task

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch 2 times, most recently from f42e490 to 3bafb8a Compare March 25, 2026 14:21

tarek-y-ismail marked this pull request as ready for review March 25, 2026 14:21

tarek-y-ismail requested a review from a team as a code owner March 25, 2026 14:21

Copilot AI review requested due to automatic review settings March 25, 2026 14:21

Copilot started reviewing on behalf of tarek-y-ismail March 25, 2026 14:22 View session

tarek-y-ismail changed the base branch from main to live-config-ini-file-changes March 25, 2026 14:24

tarek-y-ismail marked this pull request as draft March 25, 2026 14:25

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch from 3bafb8a to 88e7411 Compare March 25, 2026 14:27

Copilot AI reviewed Mar 25, 2026

View reviewed changes

tarek-y-ismail force-pushed the live-config-ini-file-changes branch 8 times, most recently from 7270cfd to 0009e12 Compare March 26, 2026 12:49

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch from 88e7411 to 3a5de42 Compare March 26, 2026 13:00

tarek-y-ismail force-pushed the live-config-ini-file-changes branch 2 times, most recently from ea3d4b1 to 49f4970 Compare March 26, 2026 14:42

tarek-y-ismail force-pushed the live-config-ini-file-changes branch from 49f4970 to ec5910c Compare March 26, 2026 15:10

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch from 3a5de42 to 4d8e03b Compare March 26, 2026 16:42

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch 2 times, most recently from 6208929 to db1da86 Compare April 16, 2026 15:10

tarek-y-ismail changed the base branch from live-config-ini-file-changes to add-config-file-store-adapter April 16, 2026 15:13

tarek-y-ismail force-pushed the add-config-file-store-adapter branch 2 times, most recently from 18f47be to 2801040 Compare April 16, 2026 15:47

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch from db1da86 to f48fb79 Compare April 16, 2026 15:53

tarek-y-ismail force-pushed the add-config-file-store-adapter branch from 2801040 to 5c5a932 Compare April 21, 2026 16:31

tarek-y-ismail and others added 13 commits April 21, 2026 18:31

Add OverrideLoader support to ConfigFile for override directory loading

cd51366

Add support for loading multiple config files in IniFile

66cbd07

Add tests for config file override and symlink handling

b717e06

Add tests for override config file deletion and renaming

3f6907d

Create override directory before adding override file in

920e892

`reloads_when_override_file_is_added`

Fail if wait_for_load times out.

2f22876

Make wait_for_load fail test on timeout in only some of the override

445ced8

config tests

Add tests for override dir deletion and relative symlinks

cde3280

- Test reload on override directory deletion at runtime - Test reload when a symlinked override file is added after startup and its target is modified - Test reload when a relative symlinked override file target is modified

Add tests for symlinked base config file handling in ConfigFile

bee7c14

pre-commit: apply automatic fixes

4119d6a

Nuke all symlink related TestOverrideConfigFile test code

22875cd

Use config file full path instead of just the name when deriving the

f17c011

base config directory

Add magnifier to demo server for testing purposes

a7f2815

tarek-y-ismail force-pushed the MIRENG-1761/live-config-override-directory branch from 2c9295a to a7f2815 Compare April 21, 2026 16:31

pre-commit: apply automatic fixes

6cf5ef4

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Live config override directory#4781

Live config override directory#4781
tarek-y-ismail wants to merge 14 commits intoadd-config-file-store-adapterfrom
MIRENG-1761/live-config-override-directory

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	base_config_directory{config_directory(base_config.filename())},
	base_config_directory{config_directory(base_config)},

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tarek-y-ismail commented Mar 18, 2026

What's new?

How to test

Checklist

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