From c36c9626704bec661164ff40860ee8abdbd9bfaf Mon Sep 17 00:00:00 2001
From: Cole Faust <colefaust@google.com>
Date: Tue, 7 Dec 2021 15:20:45 -0800
Subject: [PATCH] Handle substitution references in mk2rbc

Bug: 201700692
Test: go test
Change-Id: I5ba5e51848e795e39f1f65dc153e4c1530066860
---
 mk2rbc/mk2rbc.go      | 28 ++++++++++++++++++++++++++++
 mk2rbc/mk2rbc_test.go | 17 +++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index d1140fab7..d5ff18105 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -1332,6 +1332,34 @@ func (ctx *parseContext) parseReference(node mkparser.Node, ref *mkparser.MakeSt
 			// TODO (asmundak): if we find many, maybe handle them.
 			return ctx.newBadExpr(node, "SOONG_CONFIG_ variables cannot be referenced, use soong_config_get instead: %s", refDump)
 		}
+		// Handle substitution references: https://www.gnu.org/software/make/manual/html_node/Substitution-Refs.html
+		if strings.Contains(refDump, ":") {
+			parts := strings.SplitN(refDump, ":", 2)
+			substParts := strings.SplitN(parts[1], "=", 2)
+			if len(substParts) < 2 || strings.Count(substParts[0], "%") > 1 {
+				return ctx.newBadExpr(node, "Invalid substitution reference")
+			}
+			if !strings.Contains(substParts[0], "%") {
+				if strings.Contains(substParts[1], "%") {
+					return ctx.newBadExpr(node, "A substitution reference must have a %% in the \"before\" part of the substitution if it has one in the \"after\" part.")
+				}
+				substParts[0] = "%" + substParts[0]
+				substParts[1] = "%" + substParts[1]
+			}
+			v := ctx.addVariable(parts[0])
+			if v == nil {
+				return ctx.newBadExpr(node, "unknown variable %s", refDump)
+			}
+			return &callExpr{
+				name:       "patsubst",
+				returnType: knownFunctions["patsubst"].returnType,
+				args: []starlarkExpr{
+					&stringLiteralExpr{literal: substParts[0]},
+					&stringLiteralExpr{literal: substParts[1]},
+					&variableRefExpr{v, ctx.lastAssignment(v.name()) != nil},
+				},
+			}
+		}
 		if v := ctx.addVariable(refDump); v != nil {
 			return &variableRefExpr{v, ctx.lastAssignment(v.name()) != nil}
 		}
diff --git a/mk2rbc/mk2rbc_test.go b/mk2rbc/mk2rbc_test.go
index 0048ad122..78444c9c6 100644
--- a/mk2rbc/mk2rbc_test.go
+++ b/mk2rbc/mk2rbc_test.go
@@ -1112,6 +1112,23 @@ def init(g, handle):
   g["TEST_VAR_2"] = ("bar" if g["TEST_VAR"] else "")
   g["TEST_VAR_3"] = ("bar" if g["TEST_VAR"] else "baz")
   g["TEST_VAR_3"] = (g["TEST_VAR_LIST"] if g["TEST_VAR"] else [])
+`,
+	},
+	{
+		desc:   "substitution references",
+		mkname: "product.mk",
+		in: `
+SOURCES := foo.c bar.c
+OBJECTS := $(SOURCES:.c=.o)
+OBJECTS2 := $(SOURCES:%.c=%.o)
+`,
+		expected: `load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["SOURCES"] = "foo.c bar.c"
+  g["OBJECTS"] = rblf.mkpatsubst("%.c", "%.o", g["SOURCES"])
+  g["OBJECTS2"] = rblf.mkpatsubst("%.c", "%.o", g["SOURCES"])
 `,
 	},
 }