Allow empty go.mod

src/Strategy/Go/Gomod.hs

@@ -53,6 +53,7 @@ import Text.Megaparsec (
   MonadParsec (eof, takeWhile1P, try),
   Parsec,
   between,
+  choice,
   chunk,
   count,
   many,
@@ -217,12 +218,19 @@ parsePackageVersion lexify = parseSemOrPseudo <|> parseNonCanonical
 
 gomodParser :: Parser Gomod
 gomodParser = do
+  let emptyGoMod = do
+        eof
+        pure ("", [])
+  let nonEmptyGoMod = do
+        _ <- lexeme (chunk "module")
+        name <- modulePath
+        _ <- scn
+        statements <- many (statement <* scn)
+        eof
+        pure (name, statements)
+
   _ <- scn
-  _ <- lexeme (chunk "module")
-  name <- modulePath
-  _ <- scn
-  statements <- many (statement <* scn)
-  eof
+  (name, statements) <- choice [nonEmptyGoMod, emptyGoMod]
 
   let statements' = concat statements
 

test/Go/GomodSpec.hs

@@ -7,15 +7,15 @@ import Data.Function ((&))
 import Data.Map.Strict qualified as Map
 import Data.SemVer (version)
 import Data.SemVer.Internal (Identifier (..))
-import Data.Text (Text)
+import Data.Text (Text, empty)
 import Data.Text.IO qualified as TIO
 import DepTypes (DepType (GoType), Dependency (..), VerConstraint (CEq))
 import Effect.Grapher (direct, evalGrapher)
 import Graphing (Graphing (..))
 import Strategy.Go.Gomod (Gomod (..), PackageVersion (..), Require (..), buildGraph, gomodParser)
 import Strategy.Go.Types (graphingGolang)
 import Test.Hspec (Spec, describe, it, runIO, shouldBe)
-import Test.Hspec.Megaparsec (shouldParse)
+import Test.Hspec.Megaparsec (shouldFailOn, shouldParse)
 import Text.Megaparsec (runParser)
 import Text.RawString.QQ (r)
 
@@ -57,6 +57,16 @@ trivialGraph = run . evalGrapher $ do
   direct $ dep "github.com/pkg/overridden" "overridden"
   direct $ dep "github.com/pkg/three/v3" "v3.0.0"
 
+emptyGomod :: Gomod
+emptyGomod =
+  Gomod
+    { modName = ""
+    , modRequires = []
+    , modReplaces = Map.empty
+    , modLocalReplaces = Map.empty
+    , modExcludes = []
+    }
+
 localReplaceGomod :: Gomod
 localReplaceGomod =
   Gomod
@@ -193,6 +203,9 @@ spec_parse = do
     it "parses a trivial example" $ do
       runParser gomodParser "" trivialInput `shouldParse` trivialGomod
 
+    it "parses empty go.mod" $ do
+      runParser gomodParser "" Data.Text.empty `shouldParse` emptyGomod
+
     it "parses each edge case" $ do
       runParser gomodParser "" edgecaseInput `shouldParse` edgeCaseGomod
 
@@ -211,6 +224,9 @@ spec_parse = do
       runParser gomodParser "" goModWithRetractComment3 `shouldParse` gomodWithRetract
       runParser gomodParser "" goModWithRetractComment4 `shouldParse` gomodWithRetract
 
+    it "fails to parse invalid go.mod" $ do
+      runParser gomodParser "" `shouldFailOn` "invalid input"
+
 gomodWithRetract :: Gomod
 gomodWithRetract =
   Gomod