Allow tests to mock filesystem

Tests can call Context.MockFileSystem to pass in a map of filenames to
contents.

Change-Id: Idd67c68f7cb43bc2117cc78336347db7e2f21991

Blueprints

@@ -8,6 +8,7 @@ bootstrap_go_package(
     pkgPath = "github.com/google/blueprint",
     srcs = [
         "context.go",
+        "fs.go",
         "live_tracker.go",
         "mangle.go",
         "module_ctx.go",

build.ninja.in

@@ -60,8 +60,8 @@ rule g.bootstrap.link
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint/pkg/github.com/google/blueprint.a $
         : g.bootstrap.compile ${g.bootstrap.srcDir}/context.go $
-        ${g.bootstrap.srcDir}/live_tracker.go ${g.bootstrap.srcDir}/mangle.go $
+        ${g.bootstrap.srcDir}/fs.go ${g.bootstrap.srcDir}/live_tracker.go $
-        ${g.bootstrap.srcDir}/module_ctx.go $
+        ${g.bootstrap.srcDir}/mangle.go ${g.bootstrap.srcDir}/module_ctx.go $
         ${g.bootstrap.srcDir}/ninja_defs.go $
         ${g.bootstrap.srcDir}/ninja_strings.go $
         ${g.bootstrap.srcDir}/ninja_writer.go $
@@ -81,7 +81,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:81:1
+# Defined: Blueprints:83:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-bootstrap/pkg/github.com/google/blueprint/bootstrap.a $
@@ -108,7 +108,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:100:1
+# Defined: Blueprints:102:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-bootstrap-bpdoc/pkg/github.com/google/blueprint/bootstrap/bpdoc.a $
@@ -128,7 +128,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:47:1
+# Defined: Blueprints:49:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-deptools/pkg/github.com/google/blueprint/deptools.a $
@@ -143,7 +143,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:31:1
+# Defined: Blueprints:33:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-parser/pkg/github.com/google/blueprint/parser.a $
@@ -161,7 +161,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:53:1
+# Defined: Blueprints:55:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-pathtools/pkg/github.com/google/blueprint/pathtools.a $
@@ -176,7 +176,7 @@ default $
 # Variant:
 # Type:    bootstrap_go_package
 # Factory: github.com/google/blueprint/bootstrap.newGoPackageModuleFactory.func1
-# Defined: Blueprints:65:1
+# Defined: Blueprints:67:1
 
 build $
         ${g.bootstrap.buildDir}/.bootstrap/blueprint-proptools/pkg/github.com/google/blueprint/proptools.a $
@@ -194,7 +194,7 @@ default $
 # Variant:
 # Type:    bootstrap_core_go_binary
 # Factory: github.com/google/blueprint/bootstrap.newGoBinaryModuleFactory.func1
-# Defined: Blueprints:143:1
+# Defined: Blueprints:145:1
 
 build ${g.bootstrap.buildDir}/.bootstrap/choosestage/obj/choosestage.a: $
         g.bootstrap.compile ${g.bootstrap.srcDir}/choosestage/choosestage.go | $
@@ -217,7 +217,7 @@ default ${g.bootstrap.BinDir}/choosestage
 # Variant:
 # Type:    bootstrap_core_go_binary
 # Factory: github.com/google/blueprint/bootstrap.newGoBinaryModuleFactory.func1
-# Defined: Blueprints:133:1
+# Defined: Blueprints:135:1
 
 build ${g.bootstrap.buildDir}/.bootstrap/gotestmain/obj/gotestmain.a: $
         g.bootstrap.compile ${g.bootstrap.srcDir}/gotestmain/gotestmain.go | $
@@ -240,7 +240,7 @@ default ${g.bootstrap.BinDir}/gotestmain
 # Variant:
 # Type:    bootstrap_core_go_binary
 # Factory: github.com/google/blueprint/bootstrap.newGoBinaryModuleFactory.func1
-# Defined: Blueprints:138:1
+# Defined: Blueprints:140:1
 
 build ${g.bootstrap.buildDir}/.bootstrap/gotestrunner/obj/gotestrunner.a: $
         g.bootstrap.compile ${g.bootstrap.srcDir}/gotestrunner/gotestrunner.go $
@@ -263,7 +263,7 @@ default ${g.bootstrap.BinDir}/gotestrunner
 # Variant:
 # Type:    bootstrap_core_go_binary
 # Factory: github.com/google/blueprint/bootstrap.newGoBinaryModuleFactory.func1
-# Defined: Blueprints:112:1
+# Defined: Blueprints:114:1
 
 build ${g.bootstrap.buildDir}/.bootstrap/minibp/obj/minibp.a: $
         g.bootstrap.compile ${g.bootstrap.srcDir}/bootstrap/minibp/main.go | $

context.go

@@ -19,7 +19,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 	"path/filepath"
 	"reflect"
 	"runtime"
@@ -98,6 +97,8 @@ type Context struct {
 
 	// set lazily by sortedModuleNames
 	cachedSortedModuleNames []string
+
+	fs fileSystem
 }
 
 // An Error describes a problem that was encountered that is related to a
@@ -246,6 +247,7 @@ func NewContext() *Context {
 		moduleGroups:     make(map[string]*moduleGroup),
 		moduleInfo:       make(map[Module]*moduleInfo),
 		moduleNinjaNames: make(map[string]*moduleGroup),
+		fs:               fs,
 	}
 
 	ctx.RegisterBottomUpMutator("blueprint_deps", blueprintDepsMutator)
@@ -711,6 +713,14 @@ loop:
 	return
 }
 
+// MockFileSystem causes the Context to replace all reads with accesses to the provided map of
+// filenames to contents stored as a byte slice.
+func (c *Context) MockFileSystem(files map[string][]byte) {
+	c.fs = &mockFS{
+		files: files,
+	}
+}
+
 // parseBlueprintFile parses a single Blueprints file, returning any errors through
 // errsCh, any defined modules through modulesCh, any sub-Blueprints files through
 // blueprintsCh, and any dependencies on Blueprints files or directories through
@@ -719,7 +729,7 @@ func (c *Context) parseBlueprintsFile(filename string, scope *parser.Scope, root
 	errsCh chan<- []error, fileCh chan<- *parser.File, blueprintsCh chan<- stringAndScope,
 	depsCh chan<- string) {
 
-	f, err := os.Open(filename)
+	f, err := c.fs.Open(filename)
 	if err != nil {
 		errsCh <- []error{err}
 		return
@@ -772,15 +782,15 @@ func (c *Context) findBuildBlueprints(dir string, build []string,
 		deps = append(deps, matchedDirs...)
 
 		for _, foundBlueprints := range matches {
-			fileInfo, err := os.Stat(foundBlueprints)
+			exists, dir, err := c.fs.Exists(foundBlueprints)
-			if os.IsNotExist(err) {
+			if err != nil {
+				errs = append(errs, err)
+			} else if !exists {
 				errs = append(errs, &Error{
 					Err: fmt.Errorf("%q not found", foundBlueprints),
 				})
 				continue
-			}
+			} else if dir {
-
-			if fileInfo.IsDir() {
 				errs = append(errs, &Error{
 					Err: fmt.Errorf("%q is a directory", foundBlueprints),
 				})
@@ -819,29 +829,34 @@ func (c *Context) findSubdirBlueprints(dir string, subdirs []string, subdirsPos
 		deps = append(deps, matchedDirs...)
 
 		for _, foundSubdir := range matches {
-			fileInfo, subdirStatErr := os.Stat(foundSubdir)
+			exists, dir, subdirStatErr := c.fs.Exists(foundSubdir)
 			if subdirStatErr != nil {
 				errs = append(errs, subdirStatErr)
 				continue
 			}
 
 			// Skip files
-			if !fileInfo.IsDir() {
+			if !dir {
 				continue
 			}
 
 			var subBlueprints string
 			if subBlueprintsName != "" {
 				subBlueprints = filepath.Join(foundSubdir, subBlueprintsName)
-				_, err = os.Stat(subBlueprints)
+				exists, _, err = c.fs.Exists(subBlueprints)
 			}
 
-			if os.IsNotExist(err) || subBlueprints == "" {
+			if err == nil && (!exists || subBlueprints == "") {
 				subBlueprints = filepath.Join(foundSubdir, "Blueprints")
-				_, err = os.Stat(subBlueprints)
+				exists, _, err = c.fs.Exists(subBlueprints)
 			}
 
-			if os.IsNotExist(err) {
+			if err != nil {
+				errs = append(errs, err)
+				continue
+			}
+
+			if !exists {
 				// There is no Blueprints file in this subdirectory.  We
 				// need to add the directory to the list of dependencies
 				// so that if someone adds a Blueprints file in the

context_test.go

@@ -109,10 +109,62 @@ func TestContextParse(t *testing.T) {
 //     |===F===|   B, D and E should not be walked.
 func TestWalkDeps(t *testing.T) {
 	ctx := NewContext()
+	ctx.MockFileSystem(map[string][]byte{
+		"Blueprints": []byte(`
+			foo_module {
+			    name: "A",
+			    deps: ["B", "C"],
+			}
+			
+			bar_module {
+			    name: "B",
+			    deps: ["D"],
+			}
+			
+			foo_module {
+			    name: "C",
+			    deps: ["E", "F"],
+			}
+			
+			foo_module {
+			    name: "D",
+			}
+			
+			bar_module {
+			    name: "E",
+			    deps: ["G"],
+			}
+			
+			foo_module {
+			    name: "F",
+			    deps: ["G"],
+			}
+			
+			foo_module {
+			    name: "G",
+			}
+		`),
+	})
+
 	ctx.RegisterModuleType("foo_module", newFooModule)
 	ctx.RegisterModuleType("bar_module", newBarModule)
-	ctx.ParseBlueprintsFiles("context_test_Blueprints")
+	_, errs := ctx.ParseBlueprintsFiles("Blueprints")
-	ctx.ResolveDependencies(nil)
+	if len(errs) > 0 {
+		t.Errorf("unexpected parse errors:")
+		for _, err := range errs {
+			t.Errorf("  %s", err)
+		}
+		t.FailNow()
+	}
+
+	errs = ctx.ResolveDependencies(nil)
+	if len(errs) > 0 {
+		t.Errorf("unexpected dep errors:")
+		for _, err := range errs {
+			t.Errorf("  %s", err)
+		}
+		t.FailNow()
+	}
 
 	var output string
 	topModule := ctx.moduleGroups["A"].modules[0]

context_test_Blueprints

@@ -1,32 +0,0 @@
-foo_module {
-    name: "A",
-    deps: ["B", "C"],
-}
-
-bar_module {
-    name: "B",
-    deps: ["D"],
-}
-
-foo_module {
-    name: "C",
-    deps: ["E", "F"],
-}
-
-foo_module {
-    name: "D",
-}
-
-bar_module {
-    name: "E",
-    deps: ["G"],
-}
-
-foo_module {
-    name: "F",
-    deps: ["G"],
-}
-
-foo_module {
-    name: "G",
-}

fs.go

@@ -0,0 +1,73 @@
+// Copyright 2016 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package blueprint
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"os"
+)
+
+// Based on Andrew Gerrand's "10 things you (probably) dont' know about Go"
+
+var fs fileSystem = osFS{}
+
+type fileSystem interface {
+	Open(name string) (io.ReadCloser, error)
+	Exists(name string) (bool, bool, error)
+}
+
+// osFS implements fileSystem using the local disk.
+type osFS struct{}
+
+func (osFS) Open(name string) (io.ReadCloser, error) { return os.Open(name) }
+func (osFS) Exists(name string) (bool, bool, error) {
+	stat, err := os.Stat(name)
+	if err == nil {
+		return true, stat.IsDir(), nil
+	} else if os.IsNotExist(err) {
+		return false, false, nil
+	} else {
+		return false, false, err
+	}
+}
+
+type mockFS struct {
+	files map[string][]byte
+}
+
+func (m mockFS) Open(name string) (io.ReadCloser, error) {
+	if f, ok := m.files[name]; ok {
+		return struct {
+			io.Closer
+			*bytes.Reader
+		}{
+			ioutil.NopCloser(nil),
+			bytes.NewReader(f),
+		}, nil
+	}
+
+	return nil, &os.PathError{
+		Op:   "open",
+		Path: name,
+		Err:  os.ErrNotExist,
+	}
+}
+
+func (m mockFS) Exists(name string) (bool, bool, error) {
+	_, ok := m.files[name]
+	return ok, false, nil
+}