modularize the config module bootstrap #141272

Shourya742 · 2025-05-20T03:14:31Z

Right now, our config module is pretty big, sitting at over 3,000 lines and doing quite a lot. This PR aims to break it down into smaller, more focused modules to make it easier to understand and work with:

types: This will hold all the core data structures for our configuration.
toml: This module will contain structures that mirror our bootstrap.toml file, along with the logic for deserializing and merging them.
config (main file): This will declare the central Config struct and house its top-level methods that interact across different config sections.
parsing: This is where the main logic for loading and validating the configuration will live.

r? @Kobzol

rustbot · 2025-05-20T03:14:37Z

This PR modifies src/bootstrap/src/core/config.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

Kobzol

I like the general direction of this. Could you perhaps split the changes into multiple commits though? It would be easier to review. Thank you :)

src/bootstrap/src/core/config/toml.rs

… with the logic for deserializing and merging them

…figuration

…level methods that interact across different config sections

Kobzol · 2025-05-22T08:00:30Z

Kind of crazy just how much code is there in config definition and parsing. The changes LGTM, but since this is a large-ish change, I'd like to hear also from other members of t-bootstrap if they are OK with it. CC @onur-ozkan @jieyouxu.

onur-ozkan · 2025-05-24T10:23:37Z

src/bootstrap/src/core/config/toml.rs

+/// Since we use `#[serde(deny_unknown_fields)]` on `TomlConfig`, we need a wrapper type
+/// for the "change-id" field to parse it even if other fields are invalid. This ensures
+/// that if deserialization fails due to other fields, we can still provide the changelogs
+/// to allow developers to potentially find the reason for the failure in the logs..
+#[derive(Deserialize, Default)]
+pub(crate) struct ChangeIdWrapper {


We have types module but this module also includes bunch of types. Right now it seems like there is no clear distinction between these modules and people will start putting things all around without having a clear clue. If we want to have module for per task, we have to make it super explicit/clear and have it well documented.

onur-ozkan · 2025-05-24T10:24:19Z

src/bootstrap/src/core/config/types.rs

+// NOTE: can't derive(Deserialize) because the intermediate trip through toml::Value only
+// deserializes i64, and derive() only generates visit_u64
+impl<'de> Deserialize<'de> for DebuginfoLevel {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        use serde::de::Error;
+
+        Ok(match Deserialize::deserialize(deserializer)? {
+            StringOrInt::String(s) if s == "none" => DebuginfoLevel::None,
+            StringOrInt::Int(0) => DebuginfoLevel::None,
+            StringOrInt::String(s) if s == "line-directives-only" => {
+                DebuginfoLevel::LineDirectivesOnly
+            }
+            StringOrInt::String(s) if s == "line-tables-only" => DebuginfoLevel::LineTablesOnly,
+            StringOrInt::String(s) if s == "limited" => DebuginfoLevel::Limited,
+            StringOrInt::Int(1) => DebuginfoLevel::Limited,
+            StringOrInt::String(s) if s == "full" => DebuginfoLevel::Full,
+            StringOrInt::Int(2) => DebuginfoLevel::Full,
+            StringOrInt::Int(n) => {
+                let other = serde::de::Unexpected::Signed(n);
+                return Err(D::Error::invalid_value(other, &"expected 0, 1, or 2"));
+            }
+            StringOrInt::String(s) => {
+                let other = serde::de::Unexpected::Str(&s);
+                return Err(D::Error::invalid_value(
+                    other,
+                    &"expected none, line-tables-only, limited, or full",
+                ));
+            }
+        })
+    }
+}


This is a parsing logic.

src/bootstrap/src/core/config/types.rs

onur-ozkan · 2025-05-24T10:25:10Z

@rustbot author

rustbot · 2025-05-24T10:25:16Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

jieyouxu · 2025-05-24T10:29:15Z

cc @clubby789

Shourya742 · 2025-05-24T15:23:25Z

@rustbot review

jieyouxu · 2025-05-26T11:55:28Z

Vibes-wise, organization seems fine to me.

onur-ozkan · 2025-05-28T07:55:09Z

I still have this concern (also see this as an additional ref). With the current approach, adding new things will always be unclear for some people. Even now, for example, we have parsing.rs and types.rs modules but some parsing logic has leaked into other modules and some types have leaked to some other modules as well.

What I would suggest instead is organizing the modules based on the configuration field. For example, mod.rs could represent the root level of the configuration and the rest could be split into the sub fields like rust.rs for [rust], llvm.rs for [llvm], target_specific.rs for things like [target.x86_64-unknown-linux-gnu], etc.

With this structure it would make it very explicit where things belong and anything that doesn't fit this rule can be easily caught during PR reviews.

rustbot assigned Kobzol May 20, 2025

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels May 20, 2025

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Shourya742 force-pushed the 2025-05-18-modularize-config-module branch from 6a1e868 to b8374d6 Compare May 20, 2025 03:17

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Kobzol reviewed May 20, 2025

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src/bootstrap/src/core/config/toml.rs Show resolved Hide resolved

Shourya742 added 4 commits May 21, 2025 22:43

extract config types from config to types.rs

5772d03

toml.rs contain structures that mirror our bootstrap.toml file, along…

6224d34

… with the logic for deserializing and merging them

parsing.rs contains the main logic for loading and validating the con…

ad25c26

…figuration

The config file declare the central Config struct and house its top-…

ad21211

…level methods that interact across different config sections

Shourya742 force-pushed the 2025-05-18-modularize-config-module branch from b8374d6 to ad21211 Compare May 21, 2025 17:19

Correct the config test imports

4250ea3

jieyouxu self-assigned this May 24, 2025

onur-ozkan reviewed May 24, 2025

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels May 24, 2025

add doc for newly added modules to config

26b95f0

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels May 24, 2025

jieyouxu removed their assignment May 26, 2025

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