Allow generic $(findstring) calls

Previously they were only allowed in if statements.
Also update the if statement condition to allow comparisons
to the search term.

Bug: 201700692
Test: go test
Change-Id: I8bee8f716819d383423c0de233ab970e49890543

mk2rbc/mk2rbc.go

@@ -105,7 +105,7 @@ var knownFunctions = map[string]struct {
 	"dist-for-goals":                      {baseName + ".mkdist_for_goals", starlarkTypeVoid, hiddenArgGlobal},
 	"enforce-product-packages-exist":      {baseName + ".enforce_product_packages_exist", starlarkTypeVoid, hiddenArgNone},
 	"error":                               {baseName + ".mkerror", starlarkTypeVoid, hiddenArgNone},
-	"findstring":                          {"!findstring", starlarkTypeInt, hiddenArgNone},
+	"findstring":                          {baseName + ".findstring", starlarkTypeString, hiddenArgNone},
 	"find-copy-subdir-files":              {baseName + ".find_and_copy", starlarkTypeList, hiddenArgNone},
 	"find-word-in-list":                   {"!find-word-in-list", starlarkTypeUnknown, hiddenArgNone}, // internal macro
 	"filter":                              {baseName + ".filter", starlarkTypeList, hiddenArgNone},
@@ -1288,8 +1288,21 @@ func (ctx *parseContext) parseCheckFindstringFuncResult(directive *mkparser.Dire
 			right: &intLiteralExpr{-1},
 			isEq:  !negate,
 		}
+	} else if s, ok := maybeString(xValue); ok {
+		if s2, ok := maybeString(xCall.args[0]); ok && s == s2 {
+			return &eqExpr{
+				left: &callExpr{
+					object:     xCall.args[1],
+					name:       "find",
+					args:       []starlarkExpr{xCall.args[0]},
+					returnType: starlarkTypeInt,
+				},
+				right: &intLiteralExpr{-1},
+				isEq:  negate,
+			}
+		}
 	}
-	return ctx.newBadExpr(directive, "findstring result can be compared only to empty: %s", xValue)
+	return ctx.newBadExpr(directive, "$(findstring) can only be compared to nothing or its first argument")
 }
 
 func (ctx *parseContext) parseCompareStripFuncResult(directive *mkparser.Directive,

mk2rbc/mk2rbc_test.go

@@ -633,15 +633,42 @@ def init(g, handle):
 		desc:   "findstring call",
 		mkname: "product.mk",
 		in: `
+result := $(findstring a,a b c)
+result := $(findstring b,x y z)
+`,
+		expected: `load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  _result = rblf.findstring("a", "a b c")
+  _result = rblf.findstring("b", "x y z")
+`,
+	},
+	{
+		desc:   "findstring in if statement",
+		mkname: "product.mk",
+		in: `
+ifeq ($(findstring foo,$(PRODUCT_PACKAGES)),)
+endif
 ifneq ($(findstring foo,$(PRODUCT_PACKAGES)),)
 endif
+ifeq ($(findstring foo,$(PRODUCT_PACKAGES)),foo)
+endif
+ifneq ($(findstring foo,$(PRODUCT_PACKAGES)),foo)
+endif
 `,
 		expected: `load("//build/make/core:product_config.rbc", "rblf")
 
 def init(g, handle):
   cfg = rblf.cfg(handle)
+  if (cfg.get("PRODUCT_PACKAGES", [])).find("foo") == -1:
+    pass
   if (cfg.get("PRODUCT_PACKAGES", [])).find("foo") != -1:
     pass
+  if (cfg.get("PRODUCT_PACKAGES", [])).find("foo") != -1:
+    pass
+  if (cfg.get("PRODUCT_PACKAGES", [])).find("foo") == -1:
+    pass
 `,
 	},
 	{