feat: add support for idiomatic go.mod file (jdx#4312)

Fix for discussion jdx#4136

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: jdx <216188+jdx@users.noreply.github.com>

mise.lock

@@ -12,13 +12,15 @@ backend = "core:bun"
 
 [tools.bun.checksums]
 "bun-darwin-aarch64.zip" = "sha256:c4d58e06c5c33885b526f4d91a38ca9ebdb9fc3fb4cd547f7d3302055c98e41c"
+"bun-linux-x64-baseline.zip" = "sha256:cad7756a6ee16f3432a328f8023fc5cd431106822eacfa6d6d3afbad6fdc24db"
 
 [tools.cargo-binstall]
 version = "1.10.22"
 backend = "aqua:cargo-bins/cargo-binstall"
 
 [tools.cargo-binstall.checksums]
 "cargo-binstall-aarch64-apple-darwin.zip" = "sha256:97ce4a2f18181f052dda266b042d8bb220e48ffe40ca75e796ae4c5e418b9e01"
+"cargo-binstall-x86_64-unknown-linux-musl.tgz" = "sha256:74d7c647c7e60bb8464fa551702fdd38a7241f5cedb2c4edc3b11639cd1dae47"
 
 [tools."cargo:cargo-edit"]
 version = "0.13.1"

src/plugins/core/go.rs

@@ -194,7 +194,19 @@ impl Backend for GoPlugin {
         })
     }
     fn idiomatic_filenames(&self) -> eyre::Result<Vec<String>> {
-        Ok(vec![".go-version".into()])
+        Ok(vec![".go-version".into(), "go.mod".into()])
+    }
+
+    fn parse_idiomatic_file(&self, path: &Path) -> eyre::Result<String> {
+        let v = match path.file_name() {
+            Some(name) if name == "go.mod" => parse_gomod_file(&file::read_to_string(path)?),
+            _ => {
+                // .go-version
+                let body = file::read_to_string(path)?;
+                body.trim().trim_start_matches('v').to_string()
+            }
+        };
+        Ok(v)
     }
 
     fn install_version_(
@@ -240,6 +252,19 @@ impl Backend for GoPlugin {
     }
 }
 
+fn parse_gomod_file(body: &str) -> String {
+    let v = body
+        .lines()
+        .find(|line| line.trim().starts_with("go "))
+        .unwrap_or_default();
+    let v = regex!(r#"^[^0-9]*"#).replace_all(v, "").trim().to_string();
+    // make sure it's like 1.23.0
+    if !regex!(r"^([0-9.])*$").is_match(&v) {
+        return "".to_string();
+    }
+    v
+}
+
 fn platform() -> &'static str {
     if cfg!(target_os = "macos") {
         "darwin"
@@ -268,3 +293,25 @@ fn ext() -> &'static str {
         "tar.gz"
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use indoc::indoc;
+
+    #[test]
+    fn test_parse_gomod_file() {
+        assert_eq!(
+            parse_gomod_file(indoc! {r#"module example.com/mymodule
+              go 1.14
+              require (
+                  example.com/othermodule v1.2.3
+                  example.com/thismodule v1.2.3
+                  example.com/thatmodule v1.2.3
+              )
+              replace example.com/thatmodule => ../thatmodule
+              exclude example.com/thismodule v1.3.0"#}),
+            "1.14"
+        );
+    }
+}