Check missing uncoditionally loaded missing modules at runtime

A potentially inherited (via dynamically calculated path) module may in turn
unconditionally load a module that does no exist in a source tree -- it is
not an error if this potentially inherited module is actually never inherited
because its dynamically calculated path will never reference it. Instead of
emitting an uncoditional `load` for a non-existent file (which is going to fail
in the Starlark parser), emit conditional load and a runtime check.

Fixes: 213922819
Test: internal
Change-Id: I92177878e199a1f00e5f0c4045c0c0daeddd6bdb

mk2rbc/mk2rbc.go

@@ -249,19 +249,19 @@ func (gctx *generationContext) emitPreamble() {
 	gctx.writef("load(%q, %q)", baseUri, baseName)
 	// Emit exactly one load statement for each URI.
 	loadedSubConfigs := make(map[string]string)
-	for _, sc := range gctx.starScript.inherited {
-		uri := sc.path
+	for _, mi := range gctx.starScript.inherited {
+		uri := mi.path
 		if m, ok := loadedSubConfigs[uri]; ok {
 			// No need to emit load statement, but fix module name.
-			sc.moduleLocalName = m
+			mi.moduleLocalName = m
 			continue
 		}
-		if sc.optional {
+		if mi.optional || mi.missing {
 			uri += "|init"
 		}
 		gctx.newLine()
-		gctx.writef("load(%q, %s = \"init\")", uri, sc.entryName())
-		loadedSubConfigs[uri] = sc.moduleLocalName
+		gctx.writef("load(%q, %s = \"init\")", uri, mi.entryName())
+		loadedSubConfigs[uri] = mi.moduleLocalName
 	}
 	gctx.write("\n")
 }
@@ -293,6 +293,20 @@ func (gctx *generationContext) emitConversionError(el ErrorLocation, message str
 	gctx.writef(`rblf.mk2rbc_error("%s", %q)`, el, message)
 }
 
+func (gctx *generationContext) emitLoadCheck(im inheritedModule) {
+	if !im.needsLoadCheck() {
+		return
+	}
+	gctx.newLine()
+	gctx.writef("if not %s:", im.entryName())
+	gctx.indentLevel++
+	gctx.newLine()
+	gctx.write(`rblf.mkerror("`, gctx.starScript.mkFile, `", "Cannot find %s" % (`)
+	im.pathExpr().emit(gctx)
+	gctx.write("))")
+	gctx.indentLevel--
+}
+
 type knownVariable struct {
 	name      string
 	class     varClass
@@ -746,11 +760,13 @@ func (ctx *parseContext) newDependentModule(path string, optional bool) *moduleI
 		moduleLocalName += fmt.Sprintf("%d", n)
 	}
 	ctx.moduleNameCount[moduleName] = n + 1
+	_, err := fs.Stat(ctx.script.sourceFS, path)
 	mi := &moduleInfo{
 		path:            modulePath,
 		originalPath:    path,
 		moduleLocalName: moduleLocalName,
 		optional:        optional,
+		missing:         err != nil,
 	}
 	ctx.dependentModules[modulePath] = mi
 	ctx.script.inherited = append(ctx.script.inherited, mi)

mk2rbc/mk2rbc_test.go

@@ -121,7 +121,7 @@ $(call inherit-product, part.mk)
 ifdef PRODUCT_NAME
 $(call inherit-product, part1.mk)
 else # Comment
-$(call inherit-product, $(LOCAL_PATH)/part1.mk)
+$(call inherit-product, $(LOCAL_PATH)/part.mk)
 endif
 `,
 		expected: `load("//build/make/core:product_config.rbc", "rblf")
@@ -132,10 +132,12 @@ def init(g, handle):
   cfg = rblf.cfg(handle)
   rblf.inherit(handle, "part", _part_init)
   if g.get("PRODUCT_NAME") != None:
+    if not _part1_init:
+      rblf.mkerror("product.mk", "Cannot find %s" % (":part1.star"))
     rblf.inherit(handle, "part1", _part1_init)
   else:
     # Comment
-    rblf.inherit(handle, "part1", _part1_init)
+    rblf.inherit(handle, "part", _part_init)
 `,
 	},
 	{
@@ -173,6 +175,8 @@ def init(g, handle):
   cfg = rblf.cfg(handle)
   _part_init(g, handle)
   if g.get("PRODUCT_NAME") != None:
+    if not _part1_init:
+      rblf.mkerror("product.mk", "Cannot find %s" % (":part1.star"))
     _part1_init(g, handle)
   else:
     if _part1_init != None:

mk2rbc/node.go

@@ -47,6 +47,7 @@ type moduleInfo struct {
 	originalPath    string // Makefile file path
 	moduleLocalName string
 	optional        bool
+	missing         bool // a module may not exist if a module that depends on it is loaded dynamically
 }
 
 func (im moduleInfo) entryName() string {
@@ -57,7 +58,8 @@ type inheritedModule interface {
 	name() string
 	entryName() string
 	emitSelect(gctx *generationContext)
-	shouldExist() bool
+	pathExpr() starlarkExpr
+	needsLoadCheck() bool
 }
 
 type inheritedStaticModule struct {
@@ -72,8 +74,12 @@ func (im inheritedStaticModule) name() string {
 func (im inheritedStaticModule) emitSelect(_ *generationContext) {
 }
 
-func (im inheritedStaticModule) shouldExist() bool {
-	return im.loadAlways
+func (im inheritedStaticModule) pathExpr() starlarkExpr {
+	return &stringLiteralExpr{im.path}
+}
+
+func (im inheritedStaticModule) needsLoadCheck() bool {
+	return im.missing
 }
 
 type inheritedDynamicModule struct {
@@ -105,20 +111,14 @@ func (i inheritedDynamicModule) emitSelect(gctx *generationContext) {
 	gctx.write(")")
 	gctx.newLine()
 	gctx.writef("(%s, %s) = _entry if _entry else (None, None)", i.name(), i.entryName())
-	if i.loadAlways {
-		gctx.newLine()
-		gctx.writef("if not %s:", i.entryName())
-		gctx.indentLevel++
-		gctx.newLine()
-		gctx.write(`rblf.mkerror("`, gctx.starScript.mkFile, `", "Cannot find %s" % (`)
-		i.path.emit(gctx)
-		gctx.write("))")
-		gctx.indentLevel--
-	}
 }
 
-func (i inheritedDynamicModule) shouldExist() bool {
-	return i.loadAlways
+func (i inheritedDynamicModule) pathExpr() starlarkExpr {
+	return &i.path
+}
+
+func (i inheritedDynamicModule) needsLoadCheck() bool {
+	return true
 }
 
 type inheritNode struct {
@@ -128,20 +128,22 @@ type inheritNode struct {
 
 func (inn *inheritNode) emit(gctx *generationContext) {
 	// Unconditional case:
+	//    maybe check that loaded
 	//    rblf.inherit(handle, <module>, module_init)
 	// Conditional case:
 	//    if <module>_init != None:
 	//      same as above
 	inn.module.emitSelect(gctx)
-
 	name := inn.module.name()
 	entry := inn.module.entryName()
-	gctx.newLine()
 	if inn.loadAlways {
+		gctx.emitLoadCheck(inn.module)
+		gctx.newLine()
 		gctx.writef("%s(handle, %s, %s)", cfnInherit, name, entry)
 		return
 	}
 
+	gctx.newLine()
 	gctx.writef("if %s:", entry)
 	gctx.indentLevel++
 	gctx.newLine()
@@ -157,12 +159,14 @@ type includeNode struct {
 func (inn *includeNode) emit(gctx *generationContext) {
 	inn.module.emitSelect(gctx)
 	entry := inn.module.entryName()
-	gctx.newLine()
 	if inn.loadAlways {
+		gctx.emitLoadCheck(inn.module)
+		gctx.newLine()
 		gctx.writef("%s(g, handle)", entry)
 		return
 	}
 
+	gctx.newLine()
 	gctx.writef("if %s != None:", entry)
 	gctx.indentLevel++
 	gctx.newLine()