add some validation checks

src/Language/Wasm/Binary.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE DuplicateRecordFields #-}
 
 module Language.Wasm.Binary (
     dumpModule,
@@ -718,7 +719,7 @@ instance Serialize LocalTypeRange where
     get = LocalTypeRange <$> getULEB128 <*> get
 
 instance Serialize Function where
-    put (Function _ locals body) = do
+    put Function {locals, body} = do
         let bs = runPut $ do
                 putVec $ map (LocalTypeRange 1) locals
                 putExpression body

src/Language/Wasm/Validate.hs

@@ -1,8 +1,71 @@
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE DuplicateRecordFields #-}
+
 module Language.Wasm.Validate (
-    validate
+    validate,
+    isValid
 ) where
 
 import Language.Wasm.Structure
+import qualified Data.Set as Set
+import Data.List (foldl')
+import qualified Data.Text.Lazy as TL
 
-validate :: Module -> Either String Module
-validate mod = Right mod
+data ValidationResult =
+    DuplicatedExportNames [String]
+    | MoreThanOneMemory
+    | MoreThanOneTable
+    | Valid
+    deriving (Show, Eq)
+
+isValid :: ValidationResult -> Bool
+isValid Valid = True
+isValid _ = False
+
+type Validator = Module -> ValidationResult
+
+shouldBeAtMostOneTable :: Validator
+shouldBeAtMostOneTable Module { imports, tables } =
+    let memImports = filter isTableImport imports in
+    if length memImports + length tables <= 1
+    then Valid
+    else MoreThanOneTable
+    where
+        isTableImport Import { desc = ImportTable _ } = True
+        isTableImport _ = False
+
+shouldBeAtMostOneMemory :: Validator
+shouldBeAtMostOneMemory Module { imports, mems } =
+    let memImports = filter isMemImport imports in
+    if length memImports + length mems <= 1
+    then Valid
+    else MoreThanOneMemory
+    where
+        isMemImport Import { desc = ImportMemory _ } = True
+        isMemImport _ = False
+
+exportNamesShouldBeDifferent :: Validator
+exportNamesShouldBeDifferent Module { exports } =
+    case foldl' go (Set.empty, []) exports of
+        (_, []) -> Valid
+        (_, dup) -> DuplicatedExportNames dup
+    where
+        go :: (Set.Set TL.Text, [String]) -> Export -> (Set.Set TL.Text, [String])
+        go (set, dup) (Export name _) =
+            if Set.member name set
+            then (set, show name : dup)
+            else (Set.insert name set, dup)
+
+validate :: Validator
+validate mod = foldl' go Valid validators
+    where
+        go :: ValidationResult -> Validator -> ValidationResult
+        go Valid validator = validator mod
+        go res _ = res
+
+        validators :: [Validator]
+        validators = [
+                shouldBeAtMostOneTable,
+                shouldBeAtMostOneMemory,
+                exportNamesShouldBeDifferent
+            ]

tests/Test.hs

@@ -13,6 +13,7 @@ import qualified Language.Wasm.Lexer as Lexer
 import qualified Language.Wasm.Parser as Parser
 import qualified Language.Wasm.Structure as Structure
 import qualified Language.Wasm.Binary as Binary
+import qualified Language.Wasm.Validate as Validate
 
 import qualified Debug.Trace as Debug
 
@@ -42,7 +43,13 @@ main = do
     let Right mod' = Binary.decodeModuleLazy $ Binary.dumpModuleLazy mod
     return $ testCase ("Dump module to binary and parse back: " ++ file) $
       assertEqual "Module matched" mod mod'
+  validationTestCases <- (`mapM` (filter (/= "import.wast") files)) $ \file -> do
+    content <- LBS.readFile $ "tests/samples/" ++ file
+    let Right mod = Parser.parseModule <$> Lexer.scanner content
+    return $ testCase ("Validate module: " ++ file) $
+      assertBool "Module matched" $ Validate.isValid $ Validate.validate mod
   defaultMain $ testGroup "tests" [
       testGroup "Syntax parsing" syntaxTestCases,
-      testGroup "Binary format" binaryTestCases
+      testGroup "Binary format" binaryTestCases,
+      testGroup "Validation" validationTestCases
     ]