Add new simplified triagebot.toml validation for PR

Author: Urgau

src/handlers/check_commits.rs

@@ -19,6 +19,7 @@ mod modified_submodule;
 mod no_mentions;
 mod no_merges;
 mod non_default_branch;
+mod validate_config;
 
 /// Key for the state in the database
 const CHECK_COMMITS_KEY: &str = "check-commits-warnings";
@@ -44,7 +45,10 @@ pub(super) async fn handle(ctx: &Context, event: &Event, config: &Config) -> any
 
     if !matches!(
         event.action,
-        IssuesAction::Opened | IssuesAction::Synchronize | IssuesAction::ReadyForReview
+        IssuesAction::Opened
+            | IssuesAction::Reopened
+            | IssuesAction::Synchronize
+            | IssuesAction::ReadyForReview
     ) || !event.issue.is_pr()
     {
         return Ok(());
@@ -112,6 +116,13 @@ pub(super) async fn handle(ctx: &Context, event: &Event, config: &Config) -> any
         }
     }
 
+    // Check if the `triagebot.toml` config is valid
+    errors.extend(
+        validate_config::validate_config(ctx, &event, diff)
+            .await
+            .context("validating the the triagebot config")?,
+    );
+
     handle_new_state(ctx, event, errors, warnings, labels).await
 }
 

src/handlers/check_commits/validate_config.rs

@@ -0,0 +1,90 @@
+//! For pull requests that have changed the triagebot.toml, validate that the
+//! changes are a valid configuration file.
+
+use crate::{
+    config::CONFIG_FILE_NAME,
+    github::FileDiff,
+    handlers::{Context, IssuesEvent},
+};
+use anyhow::{Context as _, bail};
+
+pub(super) async fn validate_config(
+    ctx: &Context,
+    event: &IssuesEvent,
+    diff: &[FileDiff],
+) -> anyhow::Result<Option<String>> {
+    if !diff.iter().any(|diff| diff.filename == CONFIG_FILE_NAME) {
+        return Ok(None);
+    }
+
+    let Some(pr_source) = &event.issue.head else {
+        bail!("expected head commit");
+    };
+    let Some(repo) = &pr_source.repo else {
+        bail!("repo is not available");
+    };
+
+    let triagebot_content = ctx
+        .github
+        .raw_file(&repo.full_name, &pr_source.sha, CONFIG_FILE_NAME)
+        .await
+        .context("{CONFIG_FILE_NAME} modified, but failed to get content")?;
+
+    let triagebot_content = triagebot_content.unwrap_or_default();
+    let triagebot_content = String::from_utf8_lossy(&*triagebot_content);
+
+    let Err(e) = toml::from_str::<crate::handlers::Config>(&triagebot_content) else {
+        return Ok(None);
+    };
+
+    let position = match e.span() {
+        // toml sometimes gives bad spans, see https://github.com/toml-rs/toml/issues/589
+        Some(span) if span != (0..0) => {
+            let (line, col) = translate_position(&triagebot_content, span.start);
+            let url = format!(
+                "https://github.com/{}/blob/{}/{CONFIG_FILE_NAME}#L{line}",
+                repo.full_name, pr_source.sha
+            );
+            format!(" at position [{line}:{col}]({url})",)
+        }
+        Some(_) | None => String::new(),
+    };
+
+    Ok(Some(format!(
+        "Invalid `triagebot.toml`{position}:\n\
+        `````\n\
+        {e}\n\
+        `````",
+    )))
+}
+
+/// Helper to translate a toml span to a `(line_no, col_no)` (1-based).
+fn translate_position(input: &str, index: usize) -> (usize, usize) {
+    if input.is_empty() {
+        return (0, index);
+    }
+
+    let safe_index = index.min(input.len() - 1);
+    let column_offset = index - safe_index;
+
+    let nl = input[0..safe_index]
+        .as_bytes()
+        .iter()
+        .rev()
+        .enumerate()
+        .find(|(_, b)| **b == b'\n')
+        .map(|(nl, _)| safe_index - nl - 1);
+    let line_start = match nl {
+        Some(nl) => nl + 1,
+        None => 0,
+    };
+    let line = input[0..line_start]
+        .as_bytes()
+        .iter()
+        .filter(|c| **c == b'\n')
+        .count();
+    let column = input[line_start..=safe_index].chars().count() - 1;
+    let column = column + column_offset;
+
+    (line + 1, column + 1)
+}