Fix ShaderLab compatible with no varying variable

packages/shader-lab/src/Ast2GLSLUtils.ts

@@ -24,20 +24,14 @@ export class Ast2GLSLUtils {
 
     // parse varying variables
     const varyingStructAstNode = context.findGlobal(vertFnAst.content.returnType.content.text)?.ast as StructAstNode;
-    if (!varyingStructAstNode) {
-      context.diagnostics.push({
-        severity: DiagnosticSeverity.Error,
-        message: "no varying struct definition",
-        token: vertFnAst.content.returnType.position
-      });
-      return "";
+    if (varyingStructAstNode) {
+      context.varyingStructInfo.structAstNode = varyingStructAstNode;
+      context.varyingStructInfo.reference = varyingStructAstNode.content.variables.map((v) => ({
+        referenced: false,
+        property: v,
+        text: `varying ${v.content.type.serialize(context)} ${v.content.variableNode.serialize(context)}`
+      }));
     }
-    context.varyingStructInfo.structAstNode = varyingStructAstNode;
-    context.varyingStructInfo.reference = varyingStructAstNode.content.variables.map((v) => ({
-      referenced: false,
-      property: v,
-      text: `varying ${v.content.type.serialize(context)} ${v.content.variableNode.serialize(context)}`
-    }));
 
     // parsing attribute variables
     vertFnAst.content.args.forEach((arg) => {
@@ -101,7 +95,7 @@ export class Ast2GLSLUtils {
     }
     context.setMainFnAst(fragFnAst);
 
-    context.varyingStructInfo.objectName = fragFnAst.content.args[0].content.name;
+    context.varyingStructInfo.objectName = fragFnAst.content.args?.[0].content.name;
     const fragmentFnStr = fragFnAst.serialize(context);
 
     // There may be global variable references in conditional macro statement, so it needs to be serialized first.

packages/shader-lab/src/ast-node/AstNode.ts

@@ -202,6 +202,18 @@ export class FnAstNode extends AstNode<IFnAstContent> {
     }
     const body = this.content.body.serialize(context);
 
+    if (
+      (this.content.returnType.content.text === "void" && this.content.returnStatement) ||
+      (this.content.returnType.content.text !== "void" && !this.content.returnStatement)
+    ) {
+      context.diagnostics.push({
+        severity: DiagnosticSeverity.Error,
+        message: "Mismatched return type",
+        token: this.position
+      });
+      throw "Mismatched return type";
+    }
+
     context.functionAstStack.pop();
     return `${returnType} ${fnName} (${args}) {\n${body}\n}`;
   }
@@ -493,6 +505,7 @@ export class FnArrayVariableAstNode extends AstNode<IFnArrayVariableAstContent>
 
 export class FnReturnStatementAstNode extends AstNode<IFnReturnStatementAstContent> {
   override _doSerialization(context: RuntimeContext): string {
+    context.currentFunctionInfo.fnAst.content.returnStatement = this;
     if (context.currentFunctionInfo.fnAst === context.currentMainFnAst) {
       return "";
     }

packages/shader-lab/src/ast-node/AstNodeContent.ts

@@ -42,7 +42,8 @@ import {
   FnVariableDeclareUnitAstNode,
   FnMacroUndefineAstNode,
   FnMacroConditionAstNode,
-  RenderQueueValueAstNode
+  RenderQueueValueAstNode,
+  FnReturnStatementAstNode
 } from "./AstNode";
 
 export interface IShaderAstContent {
@@ -111,6 +112,7 @@ export interface IFnAstContent {
   name: string;
   args: FnArgAstNode[];
   body: AstNode;
+  returnStatement?: FnReturnStatementAstNode;
 }
 
 export interface IFnBodyAstContent {

tests/src/shader-lab/ShaderLab.test.ts

@@ -200,4 +200,9 @@ describe("ShaderLab", () => {
     const demoShader = fs.readFileSync(path.join(__dirname, "shaders/triangle.shader")).toString();
     glslValidate(demoShader, shaderLab);
   });
+
+  it("No frag shader args", () => {
+    const demoShader = fs.readFileSync(path.join(__dirname, "shaders/noFragArgs.shader")).toString();
+    glslValidate(demoShader, shaderLab);
+  });
 });

tests/src/shader-lab/shaders/noFragArgs.shader

@@ -0,0 +1,30 @@
+Shader "Test-Default" {
+  Tags { ReplaceTag = "transparent" }
+  SubShader "Default" {
+    Pass "test" {
+      Tags { ReplaceTag = "opaque" }
+      mat4 renderer_MVPMat;
+
+      struct a2v {
+        vec4 POSITION;
+      }
+
+      // struct v2f {
+      //   vec2 uv;
+      // }
+
+      VertexShader = vert;
+      FragmentShader = frag;
+
+      void vert(a2v v) {
+        gl_Position = renderer_MVPMat * v.POSITION;
+      }
+
+      void frag() {
+        vec3 grayColor = vec3(0.299, 0.587, 0.114);
+        float gray = dot(grayColor, gl_FragColor.rgb);
+        gl_FragColor = vec4(gray, gray, gray, gl_FragColor.a);
+      }
+    }
+  }
+}

tests/src/shader-lab/shaders/planarShadow.shader

@@ -123,6 +123,7 @@ Shader "PlanarShadow" {
         // shadow color
         o.color = u_planarShadowColor;
         o.color.a *= falloff;
+        return o;
       }
 
       VertexShader = vert;