feat(coverage): Run with Coverage and report import for Ruby (SimpleCov) (#1535)

Ruby had no coverage runner. Run with Coverage now works for ruby, bundle, rake, rspec and rails test configurations through SimpleCov, read from its .resultset.json (lines and branches). A project that starts SimpleCov itself keeps its own setup; otherwise a small preload starts it and writes the report to the IDE's run directory, so nothing is written into the project. The preload is loaded through RUBYLIB and a bare -r in RUBYOPT, because RUBYOPT can't take the spaces in the macOS data directory, and it steps aside in the bundle exec launcher, which loads it before Bundler puts the project's gems on the load path. A CI .resultset.json can be imported through Import a Coverage Report.

Co-authored-by: kjeldahl <19719+kjeldahl@users.noreply.github.com>

crates/ide-coverage/src/import.rs

@@ -1,8 +1,8 @@
 //! "Import a report collected in CI from disk": the format is sniffed from the
-//! content (lcov, Go cover profile, JaCoCo XML) and paths recorded on another
+//! content (lcov, Go cover profile, JaCoCo XML, SimpleCov resultset) and paths recorded on another
 //! machine are mapped into the project by their longest existing suffix.
 
-use crate::{Accumulator, CoverageSuite, goprofile, jacoco, lcov};
+use crate::{Accumulator, CoverageSuite, goprofile, jacoco, lcov, simplecov};
 use ide_core::{IdeError, IdeResult};
 use std::path::{Component, Path, PathBuf};
 
@@ -11,6 +11,7 @@ pub(crate) enum Format {
     Lcov,
     GoProfile,
     Jacoco,
+    SimpleCov,
 }
 
 pub(crate) fn detect(text: &str) -> Option<Format> {
@@ -18,6 +19,9 @@ pub(crate) fn detect(text: &str) -> Option<Format> {
     if head.starts_with('<') {
         return head.contains("<report").then_some(Format::Jacoco);
     }
+    if head.starts_with('{') {
+        return head.contains("\"coverage\"").then_some(Format::SimpleCov);
+    }
     let first = head.lines().next().unwrap_or_default();
     if first.starts_with("mode:") {
         return Some(Format::GoProfile);
@@ -30,6 +34,7 @@ pub fn import(path: &Path, root: &Path) -> IdeResult<CoverageSuite> {
     let text = std::fs::read_to_string(path)?;
     let mut suite = match detect(&text) {
         Some(Format::Lcov) => lcov::parse(&text, root).finish("lcov"),
+        Some(Format::SimpleCov) => simplecov::parse(&text, root)?.finish("SimpleCov"),
         Some(Format::GoProfile) => {
             let (module, module_dir) = go_module_for(root, &text);
             goprofile::parse(&text, &module, &module_dir).finish("go test -cover")
@@ -50,7 +55,7 @@ pub fn import(path: &Path, root: &Path) -> IdeResult<CoverageSuite> {
         }
         None => {
             return Err(IdeError::invalid(format!(
-                "{} is not an lcov tracefile, Go cover profile or JaCoCo XML report",
+                "{} is not an lcov tracefile, Go cover profile, JaCoCo XML report or SimpleCov resultset",
                 path.display()
             )));
         }
@@ -125,9 +130,29 @@ mod tests {
             Some(Format::Jacoco)
         );
         assert_eq!(detect("<?xml version=\"1.0\"?><coverage/>"), None);
+        assert_eq!(detect("{\"RSpec\": {\"coverage\": {}}}"), Some(Format::SimpleCov));
+        assert_eq!(detect("{\"name\": \"package.json\"}"), None);
         assert_eq!(detect("hello"), None);
     }
 
+    #[test]
+    fn imports_ci_simplecov_with_foreign_paths() {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path().join("app");
+        std::fs::create_dir_all(root.join("lib")).unwrap();
+        std::fs::write(root.join("lib/a.rb"), "").unwrap();
+        let report = tmp.path().join(".resultset.json");
+        std::fs::write(
+            &report,
+            r#"{"RSpec":{"coverage":{"/home/runner/work/app/app/lib/a.rb":{"lines":[null,1,0]}}}}"#,
+        )
+        .unwrap();
+        let suite = import(&report, &root).unwrap();
+        assert_eq!(suite.runner, "SimpleCov");
+        assert_eq!(suite.files[0].path.as_ref() as &Path, root.join("lib/a.rb"));
+        assert_eq!((suite.files[0].lines_total, suite.files[0].lines_covered), (2, 1));
+    }
+
     #[test]
     fn imports_ci_lcov_with_foreign_paths() {
         let tmp = tempfile::tempdir().unwrap();

crates/ide-coverage/src/lib.rs

@@ -10,6 +10,7 @@
 //! | JS / TS (vitest, jest scripts) | the runner's `--coverage` | lcov |
 //! | Node.js scripts | `c8` | lcov |
 //! | Python (pytest, scripts) | coverage.py (`coverage run`, then `coverage lcov`) | lcov |
+//! | Ruby (rspec, minitest, rake, scripts) | SimpleCov (`coverage/.resultset.json`) | SimpleCov resultset |
 //! | Go (`go test`) | `-coverprofile` | Go cover profile |
 //! | Maven / Gradle tests | JaCoCo (plugin goals / an init script) | JaCoCo XML |
 //!
@@ -20,6 +21,7 @@ mod import;
 mod jacoco;
 mod lcov;
 mod plan;
+mod simplecov;
 
 pub use import::import;
 pub use plan::prepare;
@@ -83,6 +85,8 @@ pub enum CoverageReportSpec {
     Lcov { runner: String, path: IpcPath, base: IpcPath },
     /// `go test -coverprofile`; import paths under `module` map to `module_dir`.
     GoProfile { path: IpcPath, module: String, module_dir: IpcPath },
+    /// SimpleCov's `.resultset.json`; relative paths resolve against `base`.
+    SimpleCov { path: IpcPath, base: IpcPath },
     /// Every JaCoCo XML report (Maven `target/site/jacoco`, Gradle `build/reports/jacoco`) under `dir`.
     Jacoco { dir: IpcPath },
     /// The tool's raw data is exported to lcov by `argv` first (coverage.py: `… -m coverage lcov -o <lcov>`).
@@ -185,6 +189,10 @@ pub fn collect(spec: &CoverageReportSpec) -> IdeResult<CoverageSuite> {
             let text = read_report(path)?;
             Ok(lcov::parse(&text, base).finish(runner))
         }
+        CoverageReportSpec::SimpleCov { path, base } => {
+            let text = read_report(path)?;
+            Ok(simplecov::parse(&text, base)?.finish("SimpleCov"))
+        }
         CoverageReportSpec::GoProfile { path, module, module_dir } => {
             let text = read_report(path)?;
             Ok(goprofile::parse(&text, module, module_dir).finish("go test -cover"))

crates/ide-coverage/src/plan.rs

@@ -67,6 +67,7 @@ pub fn prepare(root: &Path, config: &RunConfig, out: &Path) -> CoveragePrepared
         "gradle" | "gradlew" => gradle(config, &dir, out),
         "npm" | "pnpm" | "yarn" | "bun" => npm(root, config, &dir, out),
         "node" | "npx" | "tsx" | "ts-node" => c8(root, config, &dir, out),
+        "ruby" | "bundle" | "rake" | "rspec" | "rails" => ruby(root, config, &dir, out),
         "deno" => unsupported("Coverage of Deno tasks is not supported yet."),
         "java" => unsupported(
             "Coverage of Java applications needs the JaCoCo agent; run a Maven or Gradle test configuration with coverage.",
@@ -234,6 +235,65 @@ fn c8(root: &Path, config: &RunConfig, dir: &Path, out: &Path) -> CoveragePrepar
     ready("c8", config, path(&c8), args, report)
 }
 
+/// Loaded first (`ide_run::ruby_preload`) when the project never starts SimpleCov itself.
+const SIMPLECOV_PRELOAD: &str = r#"# Written by OpenIDEA for Run with Coverage.
+begin
+  require "simplecov"
+rescue LoadError
+  # `bundle exec` is a Ruby process too and loads this before Bundler puts the project's gems on
+  # the load path; the Ruby it starts loads bundler/setup first and finds SimpleCov.
+  return
+end
+SimpleCov.coverage_dir(ENV.fetch("OPENIDEA_COVERAGE_DIR"))
+SimpleCov.start do
+  add_filter %r{^/(test|spec|features)/}
+  enable_coverage :branch
+end
+"#;
+
+/// Files where a project conventionally starts SimpleCov.
+const SIMPLECOV_STARTERS: &[&str] =
+    &[".simplecov", "spec/spec_helper.rb", "spec/rails_helper.rb", "test/test_helper.rb", "test/minitest_helper.rb"];
+
+fn ruby(root: &Path, config: &RunConfig, dir: &Path, out: &Path) -> CoveragePrepared {
+    let bundled = [dir, root].iter().any(|d| d.join("Gemfile").is_file());
+    let mentions = |file: &str| {
+        [dir, root].iter().any(|d| std::fs::read_to_string(d.join(file)).is_ok_and(|t| t.contains("simplecov")))
+    };
+    if bundled && !mentions("Gemfile.lock") && !mentions("Gemfile") {
+        return missing(
+            "simplecov",
+            "Ruby coverage needs the simplecov gem in the project's Gemfile.",
+            Some((vec![s("bundle"), s("add"), s("simplecov"), s("--group"), s("test")], dir)),
+        );
+    }
+    let starts = |d: &Path| {
+        SIMPLECOV_STARTERS.iter().any(|f| {
+            std::fs::read_to_string(d.join(f))
+                .is_ok_and(|t| t.contains("SimpleCov.start") || f.starts_with(".simplecov"))
+        })
+    };
+    let mut config = config.clone();
+    let resultset = if [dir, root].iter().any(|d| starts(d)) {
+        // The project's own configuration decides where the report goes (default `coverage/`).
+        // Drop the previous run's data: SimpleCov merges into it.
+        let results = dir.join("coverage");
+        let _ = std::fs::remove_file(results.join(".resultset.json"));
+        results.join(".resultset.json")
+    } else {
+        let preload = out.join("openidea_simplecov.rb");
+        if let Err(e) = std::fs::write(&preload, SIMPLECOV_PRELOAD) {
+            return unsupported(format!("Cannot write the SimpleCov preload: {e}"));
+        }
+        config.env.insert(s("OPENIDEA_COVERAGE_DIR"), path(out));
+        // `out` lives under the IDE's data directory, which may have spaces (RUBYOPT cannot take them).
+        ide_run::ruby_preload::add(&mut config.env, out, "openidea_simplecov", true);
+        out.join(".resultset.json")
+    };
+    let report = CoverageReportSpec::SimpleCov { path: resultset.into(), base: dir.to_path_buf().into() };
+    ready("SimpleCov", &config, config.command.clone(), config.args.clone(), report)
+}
+
 fn python(config: &RunConfig, dir: &Path, out: &Path, py: wrap::PythonCommand) -> CoveragePrepared {
     if py.target.is_empty() {
         return unsupported("Coverage needs a Python script or module to run.");
@@ -398,6 +458,74 @@ mod tests {
         ));
     }
 
+    /// `bundle exec` loads the preload before Bundler sets up the project's gems: without SimpleCov
+    /// on the load path it must step aside instead of failing the launcher.
+    #[test]
+    fn simplecov_preload_tolerates_a_ruby_without_the_gem() {
+        let dir = tempfile::tempdir().unwrap();
+        let out = dir.path().join("out dir");
+        std::fs::create_dir_all(&out).unwrap();
+        std::fs::write(out.join("openidea_simplecov.rb"), SIMPLECOV_PRELOAD).unwrap();
+        let status = std::process::Command::new("ruby")
+            .args(["-e", "exit 0"])
+            .env("RUBYLIB", &out)
+            .env("RUBYOPT", "-ropenidea_simplecov")
+            .env("OPENIDEA_COVERAGE_DIR", &out)
+            .env("GEM_HOME", dir.path().join("empty gems"))
+            .env("GEM_PATH", dir.path().join("empty gems"))
+            .status();
+        // No Ruby on this machine: nothing to check.
+        let Ok(status) = status else { return };
+        assert!(status.success());
+    }
+
+    #[test]
+    fn ruby_runs_get_simplecov() {
+        let dir = tempfile::tempdir().unwrap();
+        let root = dir.path();
+        // The IDE's data directory has spaces on macOS (`Application Support`).
+        let out = root.join("out dir");
+        std::fs::create_dir_all(&out).unwrap();
+        std::fs::write(root.join("Gemfile"), "source 'https://rubygems.org'\n").unwrap();
+        let config = cfg("rspec", "bundle", &["exec", "rspec"]);
+        // Bundler project without the gem: install hint.
+        match prepare(root, &config, &out) {
+            CoveragePrepared::MissingTool { tool, install: Some(i), .. } => {
+                assert_eq!(tool, "simplecov");
+                assert_eq!(i.args, ["add", "simplecov", "--group", "test"]);
+            }
+            other => panic!("{other:?}"),
+        }
+        // Gem present, never started: preloaded through RUBYOPT, report in `out`.
+        std::fs::write(root.join("Gemfile"), "gem 'simplecov'\n").unwrap();
+        let p = prepare(root, &config, &out);
+        let (l, report) = launch(&p);
+        assert_eq!(
+            (l.command.as_str(), l.args.as_slice()),
+            ("bundle", ["exec".to_owned(), "rspec".to_owned()].as_slice())
+        );
+        assert!(l.env["RUBYOPT"].contains("-ropenidea_simplecov"));
+        assert!(std::env::split_paths(&l.env["RUBYLIB"]).any(|d| d == out));
+        assert_eq!(l.env["OPENIDEA_COVERAGE_DIR"], out.to_string_lossy());
+        assert!(out.join("openidea_simplecov.rb").is_file());
+        assert!(
+            matches!(report, CoverageReportSpec::SimpleCov { path, .. } if (path.as_ref() as &Path).starts_with(&out))
+        );
+        // Started by the project: untouched environment, stale data dropped, report in `coverage/`.
+        std::fs::create_dir_all(root.join("test")).unwrap();
+        std::fs::create_dir_all(root.join("coverage")).unwrap();
+        std::fs::write(root.join("coverage/.resultset.json"), "{}").unwrap();
+        std::fs::write(root.join("test/test_helper.rb"), "require 'simplecov'\nSimpleCov.start\n").unwrap();
+        let p = prepare(root, &cfg("ruby", "ruby", &["-Ilib", "test/a_test.rb"]), &out);
+        let (l, report) = launch(&p);
+        assert!(!l.env.contains_key("RUBYOPT"));
+        assert_eq!(l.args, ["-Ilib", "test/a_test.rb"]);
+        assert!(!root.join("coverage/.resultset.json").exists());
+        assert!(
+            matches!(report, CoverageReportSpec::SimpleCov { path, .. } if (path.as_ref() as &Path).ends_with("coverage/.resultset.json"))
+        );
+    }
+
     #[test]
     fn unknown_commands_are_unsupported() {
         let dir = tempfile::tempdir().unwrap();

crates/ide-coverage/src/simplecov.rs

@@ -0,0 +1,74 @@
+//! SimpleCov's `coverage/.resultset.json`:
+//!
+//! ```json
+//! { "RSpec": { "timestamp": 1, "coverage": {
+//!     "/abs/lib/a.rb": { "lines": [null, 1, 0],
+//!                        "branches": { "[:if, 0, 3, 4, 3, 20]": { "[:then, 1, 4, 6, 4, 9]": 1, "[:else, 2, 6, 6, 6, 9]": 0 } } },
+//!     "/abs/lib/legacy.rb": [null, 1] } } }
+//! ```
+//!
+//! `lines[i]` is line `i + 1` (`null` = not relevant), so the index is already 0-based.
+//! A branch belongs to the line its condition starts on (third number of its key).
+
+use crate::Accumulator;
+use ide_core::{IdeError, IdeResult};
+use serde_json::Value;
+use std::path::Path;
+
+/// Start line (1-based) of a `"[:if, 0, 3, 4, 3, 20]"` branch key.
+fn start_line(key: &str) -> Option<u32> {
+    key.trim_matches(['[', ']']).split(',').nth(2)?.trim().parse().ok()
+}
+
+pub(crate) fn parse(text: &str, base: &Path) -> IdeResult<Accumulator> {
+    let json: Value = serde_json::from_str(text).map_err(|e| IdeError::invalid(format!("SimpleCov resultset: {e}")))?;
+    let mut acc = Accumulator::default();
+    // One entry per test command ("RSpec", "Minitest", …); their coverage is merged.
+    for suite in json.as_object().into_iter().flat_map(|o| o.values()) {
+        let Some(files) = suite.get("coverage").and_then(Value::as_object) else { continue };
+        for (name, data) in files {
+            let p = Path::new(name);
+            let path = if p.is_absolute() { p.to_path_buf() } else { base.join(p) };
+            acc.file(&path);
+            let lines = data.get("lines").or(Some(data)).and_then(Value::as_array);
+            for (i, hits) in lines.into_iter().flatten().enumerate() {
+                if let Some(hits) = hits.as_u64() {
+                    acc.line(&path, i as u32, hits);
+                }
+            }
+            for (cond, branches) in data.get("branches").and_then(Value::as_object).into_iter().flatten() {
+                let Some(line) = start_line(cond) else { continue };
+                for (branch, hits) in branches.as_object().into_iter().flatten() {
+                    acc.has_branches = true;
+                    acc.branch(&path, line.saturating_sub(1), format!("{cond}/{branch}"), hits.as_u64() > Some(0));
+                }
+            }
+        }
+    }
+    Ok(acc)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn reads_lines_branches_and_merges_suites() {
+        let text = r#"{
+          "RSpec": {"coverage": {"/p/lib/a.rb": {"lines": [null, 1, 0],
+            "branches": {"[:if, 0, 2, 4, 2, 20]": {"[:then, 1, 2, 6, 2, 9]": 1, "[:else, 2, 2, 6, 2, 9]": 0}}}}},
+          "Minitest": {"coverage": {"/p/lib/a.rb": {"lines": [null, 2, 3]}, "lib/old.rb": [1, null]}}
+        }"#;
+        let suite = parse(text, Path::new("/p")).unwrap().finish("SimpleCov");
+        assert_eq!(suite.files.len(), 2);
+        let a = suite.files.iter().find(|f| (f.path.as_ref() as &Path).ends_with("a.rb")).unwrap();
+        assert_eq!(a.lines.iter().map(|l| (l.line, l.hits)).collect::<Vec<_>>(), [(1, 3), (2, 3)]);
+        assert_eq!((a.branches_total, a.branches_covered), (2, 1));
+        assert_eq!(a.lines[0].branches_total, 2);
+        let old = suite.files.iter().find(|f| (f.path.as_ref() as &Path).ends_with("lib/old.rb")).unwrap();
+        assert_eq!(old.path.as_ref() as &Path, Path::new("/p/lib/old.rb"));
+        assert_eq!(old.lines[0].hits, 1);
+        assert!(suite.has_branches);
+        assert!(parse("nope", Path::new("/p")).is_err());
+    }
+}

crates/ide-host/src/ops/coverage.rs

@@ -32,7 +32,7 @@ pub async fn coverage_collect(host: &Host, window: &str, report: CoverageReportS
     blocking(move || ide_coverage::collect(&report)).await
 }
 
-/// Reads a report collected elsewhere (CI): lcov, a Go cover profile or JaCoCo XML,
+/// Reads a report collected elsewhere (CI): lcov, a Go cover profile, JaCoCo XML or a SimpleCov resultset,
 /// with paths mapped into this project.
 pub async fn coverage_import(host: &Host, window: &str, path: IpcPath) -> IdeResult<CoverageSuite> {
     let root = host.project(window)?.root.clone();

crates/ide-run/src/lib.rs

@@ -12,6 +12,7 @@ pub mod java_cmdline;
 pub mod junit;
 mod process;
 pub mod python_path;
+pub mod ruby_preload;
 pub mod tomcat;
 mod utf8;
 pub mod which;

crates/ide-run/src/ruby_preload.rs

@@ -0,0 +1,61 @@
+//! Loads a Ruby file into a launched process without touching the project: the directory goes on
+//! `RUBYLIB` and `RUBYOPT` gets the bare feature name (`-ropenidea_hook`).
+//!
+//! `RUBYOPT` is split at spaces with no quoting, so an absolute path in it (`-r/…/Application
+//! Support/…/hook.rb`, where the IDE keeps its data) makes Ruby fail with `invalid switch in RUBYOPT`.
+//! `RUBYLIB` is a path list and takes spaces.
+use std::collections::BTreeMap;
+use std::path::{Path, PathBuf};
+
+/// Makes `feature` (a file `<dir>/<feature>.rb`) load first in every Ruby the process starts.
+/// `inherit`: the process also sees the IDE's own environment, whose `RUBYLIB` / `RUBYOPT` stay.
+pub fn add(env: &mut BTreeMap<String, String>, dir: &Path, feature: &str, inherit: bool) {
+    let mut inherited = if inherit { crate::system_env() } else { BTreeMap::new() };
+    let mut existing = |name: &str| env.get(name).cloned().or_else(|| inherited.remove(name)).filter(|v| !v.is_empty());
+
+    let mut dirs: Vec<PathBuf> = vec![dir.to_path_buf()];
+    if let Some(lib) = existing("RUBYLIB") {
+        for d in std::env::split_paths(&lib) {
+            if !dirs.contains(&d) {
+                dirs.push(d);
+            }
+        }
+    }
+    let rubyopt = existing("RUBYOPT");
+    if let Ok(joined) = std::env::join_paths(dirs) {
+        env.insert("RUBYLIB".into(), joined.to_string_lossy().into_owned());
+    }
+    let option = format!("-r{feature}");
+    let value = match rubyopt {
+        Some(e) if e.split_whitespace().any(|o| o == option) => e,
+        Some(e) => format!("{e} {option}"),
+        None => option,
+    };
+    env.insert("RUBYOPT".into(), value);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn a_directory_with_spaces_goes_on_rubylib_not_into_rubyopt() {
+        let dir = Path::new("/Users/me/Library/Application Support/ide/ruby");
+        let mut env = BTreeMap::new();
+        add(&mut env, dir, "openidea_hook", false);
+        assert_eq!(env["RUBYLIB"], dir.to_string_lossy());
+        assert_eq!(env["RUBYOPT"], "-ropenidea_hook");
+        assert!(!env["RUBYOPT"].contains(' '));
+    }
+
+    #[test]
+    fn keeps_existing_settings_and_adds_once() {
+        // Path lists use the platform's separator (`;` on Windows).
+        let list = |dirs: &[&str]| std::env::join_paths(dirs).unwrap().to_string_lossy().into_owned();
+        let mut env = BTreeMap::from([("RUBYLIB".into(), list(&["/a", "/b"])), ("RUBYOPT".into(), "-w".into())]);
+        add(&mut env, Path::new("/hook"), "h", false);
+        add(&mut env, Path::new("/hook"), "h", false);
+        assert_eq!(env["RUBYLIB"], list(&["/hook", "/a", "/b"]));
+        assert_eq!(env["RUBYOPT"], "-w -rh");
+    }
+}

src/bindings.ts

@@ -2426,6 +2426,8 @@ export type CoverageReportSpec =
 { kind: "lcov"; runner: string; path: IpcPath; base: IpcPath } | 
 /**  `go test -coverprofile`; import paths under `module` map to `module_dir`. */
 { kind: "goProfile"; path: IpcPath; module: string; moduleDir: IpcPath } | 
+/**  SimpleCov's `.resultset.json`; relative paths resolve against `base`. */
+{ kind: "simpleCov"; path: IpcPath; base: IpcPath } | 
 /**  Every JaCoCo XML report (Maven `target/site/jacoco`, Gradle `build/reports/jacoco`) under `dir`. */
 { kind: "jacoco"; dir: IpcPath } | 
 /**  The tool's raw data is exported to lcov by `argv` first (coverage.py: `… -m coverage lcov -o <lcov>`). */

src/features/coverage/coverage.test.ts

@@ -57,6 +57,9 @@ describe("coverageSupports", () => {
     expect(coverageSupports(cfg("pnpm", ["run", "dev"]))).toBe(false);
     expect(coverageSupports(cfg("/v/bin/python3", ["-m", "pytest"]))).toBe(true);
     expect(coverageSupports(cfg("uv", ["run", "pytest"]))).toBe(true);
+    expect(coverageSupports(cfg("/v/bin/ruby", ["-Ilib", "test/a_test.rb"]))).toBe(true);
+    expect(coverageSupports(cfg("bundle", ["exec", "rspec"], { isTest: true }))).toBe(true);
+    expect(coverageSupports(cfg("bundle", ["exec", "rake", "db:migrate"]))).toBe(false);
     expect(coverageSupports(cfg("make", ["test"]))).toBe(false);
   });
 });

src/features/coverage/model.ts

@@ -16,7 +16,7 @@ const runsJvmTests = (args: readonly string[]) =>
 /**
  * Whether a coverage runner is known for `config` (cheap; the backend decides for real):
  * cargo test / run / nextest, go test, Maven / Gradle tests, package.json test scripts,
- * Node.js programs and Python.
+ * Node.js programs, Python and Ruby (scripts, rspec, test rake tasks).
  */
 export function coverageSupports(config: Pick<RunConfig, "command" | "args" | "kind" | "isTest">): boolean {
   const program = programName(config.command);
@@ -43,6 +43,13 @@ export function coverageSupports(config: Pick<RunConfig, "command" | "args" | "k
     case "tsx":
     case "ts-node":
       return true;
+    case "ruby":
+    case "rspec":
+      return true;
+    case "bundle":
+    case "rake":
+    case "rails":
+      return config.isTest;
   }
   return (
     config.kind === "python" ||

src/features/coverage/reports.tsx

@@ -1,6 +1,6 @@
 /**
  * Coverage reports collected elsewhere: "Import a report collected in CI from
- * disk" (lcov, JaCoCo XML, Go cover profile) and "Manage Coverage Reports"
+ * disk" (lcov, JaCoCo XML, Go cover profile, SimpleCov) and "Manage Coverage Reports"
  * (choose the shown suite, delete suites and remembered imports).
  */
 import { useMemo, useState } from "react";
@@ -35,7 +35,7 @@ async function pickReport(): Promise<string | null> {
     filters: [
       {
         name: "Coverage reports (lcov, JaCoCo XML, Go cover profile)",
-        extensions: ["info", "lcov", "xml", "out", "txt", "cov", "coverprofile"],
+        extensions: ["info", "lcov", "xml", "out", "txt", "cov", "coverprofile", "json"],
       },
       { name: "All files", extensions: ["*"] },
     ],