Make runtime effect error tests simpler / more explicit

I've wanted to write a few of these lately, and (just like the shader
tests later in the file), the rigid structure was making things
difficult. It also forced some of these to be overly clever (like
commenting out main). Switch to just providing all of the SkSL for each
test case.

Change-Id: I8aff34224fa6efbdc4d67628744a9cf499eb53b5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/333796
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

tests/SkRuntimeEffectTest.cpp

@@ -21,69 +21,71 @@
 #include <thread>
 
 DEF_TEST(SkRuntimeEffectInvalid, r) {
-    auto test = [r](const char* hdr, const char* body, const char* expected) {
-        SkString src = SkStringPrintf("%s half4 main(float2 p) { %s return half4(0); }",
-                                      hdr, body);
-        auto[effect, errorText] = SkRuntimeEffect::Make(src);
+    auto test = [r](const char* src, const char* expected) {
+        auto[effect, errorText] = SkRuntimeEffect::Make(SkString(src));
         REPORTER_ASSERT(r, !effect);
         REPORTER_ASSERT(r, errorText.contains(expected),
                         "Expected error message to contain \"%s\". Actual message: \"%s\"",
                         expected, errorText.c_str());
     };
 
+#define EMPTY_MAIN "half4 main() { return half4(0); }"
+
     // Features that are only allowed in .fp files (key, in uniform, ctype, when, tracked).
     // Ensure that these fail, and the error messages contain the relevant keyword.
-    test("layout(key) in bool Input;", "", "key");
-    test("in uniform float Input;", "", "in uniform");
-    test("layout(ctype=SkRect) float4 Input;", "", "ctype");
-    test("in bool Flag; layout(when=Flag) uniform float Input;", "", "when");
-    test("layout(tracked) uniform float Input;", "", "tracked");
+    test("layout(key) in bool Input;"                           EMPTY_MAIN, "key");
+    test("in uniform float Input;"                              EMPTY_MAIN, "in uniform");
+    test("layout(ctype=SkRect) float4 Input;"                   EMPTY_MAIN, "ctype");
+    test("in bool Flag; layout(when=Flag) uniform float Input;" EMPTY_MAIN, "when");
+    test("layout(tracked) uniform float Input;"                 EMPTY_MAIN, "tracked");
 
     // GLSL types like sampler2D and texture2D are not allowed anywhere:
-    test("uniform sampler2D s;", "", "no type named 'sampler2D'");
-    test("uniform texture2D s;", "", "no type named 'texture2D'");
+    test("uniform sampler2D s;" EMPTY_MAIN, "no type named 'sampler2D'");
+    test("uniform texture2D s;" EMPTY_MAIN, "no type named 'texture2D'");
 
     // Runtime SkSL supports a limited set of uniform types. No bool, or int, for example:
-    test("uniform bool b;", "", "uniform");
-    test("uniform int i;", "", "uniform");
+    test("uniform bool b;" EMPTY_MAIN, "uniform");
+    test("uniform int i;"  EMPTY_MAIN, "uniform");
 
     // 'in' variables aren't allowed at all:
-    test("in bool b;", "", "'in'");
-    test("in float f;", "", "'in'");
-    test("in float2 v;", "", "'in'");
-    test("in half3x3 m;", "", "'in'");
+    test("in bool b;"    EMPTY_MAIN, "'in'");
+    test("in float f;"   EMPTY_MAIN, "'in'");
+    test("in float2 v;"  EMPTY_MAIN, "'in'");
+    test("in half3x3 m;" EMPTY_MAIN, "'in'");
 
     // 'marker' is only permitted on float4x4 uniforms
-    test("layout(marker=local_to_world) uniform float3x3 localToWorld;", "", "float4x4");
+    test("layout(marker=local_to_world) uniform float3x3 localToWorld;" EMPTY_MAIN, "float4x4");
 
-    test("float missing();", "p.x = missing();", "undefined function");
+    test("half4 missing(); half4 main() { return missing(); }", "undefined function");
 
     // Shouldn't be possible to create an SkRuntimeEffect without "main"
-    test("//", "", "main");
+    test("", "main");
 
     // Various places that shaders (fragmentProcessors) should not be allowed
-    test("",
-         "shader child;",
+    test("half4 main() { shader child; return sample(child); }",
          "must be global");
-    test("uniform shader child; half4 helper(shader fp) { return sample(fp); }",
-         "half4 color = helper(child);",
+    test("uniform shader child; half4 helper(shader fp) { return sample(fp); }"
+         "half4 main() { return helper(child); }",
          "parameter");
-    test("uniform shader child; shader get_child() { return child; }",
-         "half4 color = sample(get_child());",
+    test("uniform shader child; shader get_child() { return child; }"
+         "half4 main() { return sample(get_child()); }",
          "return");
-    test("uniform shader child;",
-         "half4 color = sample(shader(child));",
+    test("uniform shader child;"
+         "half4 main() { return sample(shader(child)); }",
          "construct");
-    test("uniform shader child1; uniform shader child2;",
-         "half4 color = sample(p.x > 10 ? child1 : child2);",
+    test("uniform shader child1; uniform shader child2;"
+         "half4 main(float2 p) { return sample(p.x > 10 ? child1 : child2); }",
          "expression");
 
     // sk_Caps is an internal system. It should not be visible to runtime effects
-    test("", "if (sk_Caps.integerSupport) { p = p.yx; }", "unknown identifier 'sk_Caps'");
+    test("half4 main() { return sk_Caps.integerSupport ? half4(1) : half4(0); }",
+         "unknown identifier 'sk_Caps'");
 
     // Errors that aren't caught until later in the compilation process (during optimize())
-    test("", "return half4(1);", "unreachable");
-    test("half badFunc() { }", "", "without returning");
+    test("half4 main() { return half4(1); return half4(0); }", "unreachable");
+    test("half4 badFunc() {}"
+         "half4 main() { return badFunc(); }",
+         "without returning");
 }
 
 DEF_TEST(SkRuntimeEffectInvalidColorFilters, r) {