internal/frontend: show module readme links in sub-units

Show a module's README links on all units within the module.

For golang/go#42968

Change-Id: I8701a04a16e1dd766b1b23ce12d52d01190840fd
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/275276
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>
Reviewed-by: Julie Qiu <julie@golang.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/internal/postgres/unit.go b/internal/postgres/unit.go
index 49e9a151..8a2fec9b 100644
--- a/internal/postgres/unit.go
+++ b/internal/postgres/unit.go
@@ -404,3 +404,28 @@ func (db *DB) getPathsInModule(ctx context.Context, modulePath, resolvedVersion
 	}
 	return paths, nil
 }
+
+// GetModuleReadme returns the README corresponding to the modulePath and version.
+func (db *DB) GetModuleReadme(ctx context.Context, modulePath, resolvedVersion string) (_ *internal.Readme, err error) {
+	defer derrors.Wrap(&err, "GetModuleReadme(ctx, %q, %q)", modulePath, resolvedVersion)
+	var readme internal.Readme
+	err = db.db.QueryRow(ctx, `
+		SELECT file_path, contents
+		FROM modules m
+		INNER JOIN units u
+		ON u.module_id = m.id
+		INNER JOIN readmes r
+		ON u.id = r.unit_id
+		WHERE
+		    m.module_path=$1
+			AND m.version=$2
+			AND m.module_path=u.path`, modulePath, resolvedVersion).Scan(&readme.Filepath, &readme.Contents)
+	switch err {
+	case sql.ErrNoRows:
+		return nil, derrors.NotFound
+	case nil:
+		return &readme, nil
+	default:
+		return nil, err
+	}
+}