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// Copyright 2021 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 android
import (
"fmt"
"reflect"
"regexp"
"sort"
"strings"
"android/soong/bazel"
"android/soong/starlark_fmt"
"github.com/google/blueprint"
)
// BazelVarExporter is a collection of configuration variables that can be exported for use in Bazel rules
type BazelVarExporter interface {
// asBazel expands strings of configuration variables into their concrete values
asBazel(Config, ExportedStringVariables, ExportedStringListVariables, ExportedConfigDependingVariables) []bazelConstant
}
// ExportedVariables is a collection of interdependent configuration variables
type ExportedVariables struct {
// Maps containing toolchain variables that are independent of the
// environment variables of the build.
exportedStringVars ExportedStringVariables
exportedStringListVars ExportedStringListVariables
exportedStringListDictVars ExportedStringListDictVariables
exportedVariableReferenceDictVars ExportedVariableReferenceDictVariables
/// Maps containing variables that are dependent on the build config.
exportedConfigDependingVars ExportedConfigDependingVariables
pctx PackageContext
}
// NewExportedVariables creats an empty ExportedVariables struct with non-nil maps
func NewExportedVariables(pctx PackageContext) ExportedVariables {
return ExportedVariables{
exportedStringVars: ExportedStringVariables{},
exportedStringListVars: ExportedStringListVariables{},
exportedStringListDictVars: ExportedStringListDictVariables{},
exportedVariableReferenceDictVars: ExportedVariableReferenceDictVariables{},
exportedConfigDependingVars: ExportedConfigDependingVariables{},
pctx: pctx,
}
}
func (ev ExportedVariables) asBazel(config Config,
stringVars ExportedStringVariables, stringListVars ExportedStringListVariables, cfgDepVars ExportedConfigDependingVariables) []bazelConstant {
ret := []bazelConstant{}
ret = append(ret, ev.exportedStringVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
ret = append(ret, ev.exportedStringListVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
ret = append(ret, ev.exportedStringListDictVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
// Note: ExportedVariableReferenceDictVars collections can only contain references to other variables and must be printed last
ret = append(ret, ev.exportedVariableReferenceDictVars.asBazel(config, stringVars, stringListVars, cfgDepVars)...)
return ret
}
// ExportStringStaticVariable declares a static string variable and exports it to
// Bazel's toolchain.
func (ev ExportedVariables) ExportStringStaticVariable(name string, value string) {
ev.pctx.StaticVariable(name, value)
ev.exportedStringVars.set(name, value)
}
// ExportStringListStaticVariable declares a static variable and exports it to
// Bazel's toolchain.
func (ev ExportedVariables) ExportStringListStaticVariable(name string, value []string) {
ev.pctx.StaticVariable(name, strings.Join(value, " "))
ev.exportedStringListVars.set(name, value)
}
// ExportVariableConfigMethod declares a variable whose value is evaluated at
// runtime via a function with access to the Config and exports it to Bazel's
// toolchain.
func (ev ExportedVariables) ExportVariableConfigMethod(name string, method interface{}) blueprint.Variable {
ev.exportedConfigDependingVars.set(name, method)
return ev.pctx.VariableConfigMethod(name, method)
}
// ExportSourcePathVariable declares a static "source path" variable and exports
// it to Bazel's toolchain.
func (ev ExportedVariables) ExportSourcePathVariable(name string, value string) {
ev.pctx.SourcePathVariable(name, value)
ev.exportedStringVars.set(name, value)
}
// ExportVariableFuncVariable declares a variable whose value is evaluated at
// runtime via a function and exports it to Bazel's toolchain.
func (ev ExportedVariables) ExportVariableFuncVariable(name string, f func() string) {
ev.exportedConfigDependingVars.set(name, func(config Config) string {
return f()
})
ev.pctx.VariableFunc(name, func(PackageVarContext) string {
return f()
})
}
// ExportString only exports a variable to Bazel, but does not declare it in Soong
func (ev ExportedVariables) ExportString(name string, value string) {
ev.exportedStringVars.set(name, value)
}
// ExportStringList only exports a variable to Bazel, but does not declare it in Soong
func (ev ExportedVariables) ExportStringList(name string, value []string) {
ev.exportedStringListVars.set(name, value)
}
// ExportStringListDict only exports a variable to Bazel, but does not declare it in Soong
func (ev ExportedVariables) ExportStringListDict(name string, value map[string][]string) {
ev.exportedStringListDictVars.set(name, value)
}
// ExportVariableReferenceDict only exports a variable to Bazel, but does not declare it in Soong
func (ev ExportedVariables) ExportVariableReferenceDict(name string, value map[string]string) {
ev.exportedVariableReferenceDictVars.set(name, value)
}
// ExportedConfigDependingVariables is a mapping of variable names to functions
// of type func(config Config) string which return the runtime-evaluated string
// value of a particular variable
type ExportedConfigDependingVariables map[string]interface{}
func (m ExportedConfigDependingVariables) set(k string, v interface{}) {
m[k] = v
}
// Ensure that string s has no invalid characters to be generated into the bzl file.
func validateCharacters(s string) string {
for _, c := range []string{`\n`, `"`, `\`} {
if strings.Contains(s, c) {
panic(fmt.Errorf("%s contains illegal character %s", s, c))
}
}
return s
}
type bazelConstant struct {
variableName string
internalDefinition string
sortLast bool
}
// ExportedStringVariables is a mapping of variable names to string values
type ExportedStringVariables map[string]string
func (m ExportedStringVariables) set(k string, v string) {
m[k] = v
}
func (m ExportedStringVariables) asBazel(config Config,
stringVars ExportedStringVariables, stringListVars ExportedStringListVariables, cfgDepVars ExportedConfigDependingVariables) []bazelConstant {
ret := make([]bazelConstant, 0, len(m))
for k, variableValue := range m {
expandedVar, err := expandVar(config, variableValue, stringVars, stringListVars, cfgDepVars)
if err != nil {
panic(fmt.Errorf("error expanding config variable %s: %s", k, err))
}
if len(expandedVar) > 1 {
panic(fmt.Errorf("%s expands to more than one string value: %s", variableValue, expandedVar))
}
ret = append(ret, bazelConstant{
variableName: k,
internalDefinition: fmt.Sprintf(`"%s"`, validateCharacters(expandedVar[0])),
})
}
return ret
}
// ExportedStringListVariables is a mapping of variable names to a list of strings
type ExportedStringListVariables map[string][]string
func (m ExportedStringListVariables) set(k string, v []string) {
m[k] = v
}
func (m ExportedStringListVariables) asBazel(config Config,
stringScope ExportedStringVariables, stringListScope ExportedStringListVariables,
exportedVars ExportedConfigDependingVariables) []bazelConstant {
ret := make([]bazelConstant, 0, len(m))
// For each exported variable, recursively expand elements in the variableValue
// list to ensure that interpolated variables are expanded according to their values
// in the variable scope.
for k, variableValue := range m {
var expandedVars []string
for _, v := range variableValue {
expandedVar, err := expandVar(config, v, stringScope, stringListScope, exportedVars)
if err != nil {
panic(fmt.Errorf("Error expanding config variable %s=%s: %s", k, v, err))
}
expandedVars = append(expandedVars, expandedVar...)
}
// Assign the list as a bzl-private variable; this variable will be exported
// out through a constants struct later.
ret = append(ret, bazelConstant{
variableName: k,
internalDefinition: starlark_fmt.PrintStringList(expandedVars, 0),
})
}
return ret
}
// ExportedStringListDictVariables is a mapping from variable names to a
// dictionary which maps keys to lists of strings
type ExportedStringListDictVariables map[string]map[string][]string
func (m ExportedStringListDictVariables) set(k string, v map[string][]string) {
m[k] = v
}
// Since dictionaries are not supported in Ninja, we do not expand variables for dictionaries
func (m ExportedStringListDictVariables) asBazel(_ Config, _ ExportedStringVariables,
_ ExportedStringListVariables, _ ExportedConfigDependingVariables) []bazelConstant {
ret := make([]bazelConstant, 0, len(m))
for k, dict := range m {
ret = append(ret, bazelConstant{
variableName: k,
internalDefinition: starlark_fmt.PrintStringListDict(dict, 0),
})
}
return ret
}
// ExportedVariableReferenceDictVariables is a mapping from variable names to a
// dictionary which references previously defined variables. This is used to
// create a Starlark output such as:
// string_var1 = "string1
// var_ref_dict_var1 = {
// "key1": string_var1
// }
// This type of variable collection must be expanded last so that it recognizes
// previously defined variables.
type ExportedVariableReferenceDictVariables map[string]map[string]string
func (m ExportedVariableReferenceDictVariables) set(k string, v map[string]string) {
m[k] = v
}
func (m ExportedVariableReferenceDictVariables) asBazel(_ Config, _ ExportedStringVariables,
_ ExportedStringListVariables, _ ExportedConfigDependingVariables) []bazelConstant {
ret := make([]bazelConstant, 0, len(m))
for n, dict := range m {
for k, v := range dict {
matches, err := variableReference(v)
if err != nil {
panic(err)
} else if !matches.matches {
panic(fmt.Errorf("Expected a variable reference, got %q", v))
} else if len(matches.fullVariableReference) != len(v) {
panic(fmt.Errorf("Expected only a variable reference, got %q", v))
}
dict[k] = "_" + matches.variable
}
ret = append(ret, bazelConstant{
variableName: n,
internalDefinition: starlark_fmt.PrintDict(dict, 0),
sortLast: true,
})
}
return ret
}
// BazelToolchainVars expands an ExportedVariables collection and returns a string
// of formatted Starlark variable definitions
func BazelToolchainVars(config Config, exportedVars ExportedVariables) string {
results := exportedVars.asBazel(
config,
exportedVars.exportedStringVars,
exportedVars.exportedStringListVars,
exportedVars.exportedConfigDependingVars,
)
sort.Slice(results, func(i, j int) bool {
if results[i].sortLast != results[j].sortLast {
return !results[i].sortLast
}
return results[i].variableName < results[j].variableName
})
definitions := make([]string, 0, len(results))
constants := make([]string, 0, len(results))
for _, b := range results {
definitions = append(definitions,
fmt.Sprintf("_%s = %s", b.variableName, b.internalDefinition))
constants = append(constants,
fmt.Sprintf("%[1]s%[2]s = _%[2]s,", starlark_fmt.Indention(1), b.variableName))
}
// Build the exported constants struct.
ret := bazel.GeneratedBazelFileWarning
ret += "\n\n"
ret += strings.Join(definitions, "\n\n")
ret += "\n\n"
ret += "constants = struct(\n"
ret += strings.Join(constants, "\n")
ret += "\n)"
return ret
}
type match struct {
matches bool
fullVariableReference string
variable string
}
func variableReference(input string) (match, error) {
// e.g. "${ExternalCflags}"
r := regexp.MustCompile(`\${(?:config\.)?([a-zA-Z0-9_]+)}`)
matches := r.FindStringSubmatch(input)
if len(matches) == 0 {
return match{}, nil
}
if len(matches) != 2 {
return match{}, fmt.Errorf("Expected to only match 1 subexpression in %s, got %d", input, len(matches)-1)
}
return match{
matches: true,
fullVariableReference: matches[0],
// Index 1 of FindStringSubmatch contains the subexpression match
// (variable name) of the capture group.
variable: matches[1],
}, nil
}
// expandVar recursively expand interpolated variables in the exportedVars scope.
//
// We're using a string slice to track the seen variables to avoid
// stackoverflow errors with infinite recursion. it's simpler to use a
// string slice than to handle a pass-by-referenced map, which would make it
// quite complex to track depth-first interpolations. It's also unlikely the
// interpolation stacks are deep (n > 1).
func expandVar(config Config, toExpand string, stringScope ExportedStringVariables,
stringListScope ExportedStringListVariables, exportedVars ExportedConfigDependingVariables) ([]string, error) {
// Internal recursive function.
var expandVarInternal func(string, map[string]bool) (string, error)
expandVarInternal = func(toExpand string, seenVars map[string]bool) (string, error) {
var ret string
remainingString := toExpand
for len(remainingString) > 0 {
matches, err := variableReference(remainingString)
if err != nil {
panic(err)
}
if !matches.matches {
return ret + remainingString, nil
}
matchIndex := strings.Index(remainingString, matches.fullVariableReference)
ret += remainingString[:matchIndex]
remainingString = remainingString[matchIndex+len(matches.fullVariableReference):]
variable := matches.variable
// toExpand contains a variable.
if _, ok := seenVars[variable]; ok {
return ret, fmt.Errorf(
"Unbounded recursive interpolation of variable: %s", variable)
}
// A map is passed-by-reference. Create a new map for
// this scope to prevent variables seen in one depth-first expansion
// to be also treated as "seen" in other depth-first traversals.
newSeenVars := map[string]bool{}
for k := range seenVars {
newSeenVars[k] = true
}
newSeenVars[variable] = true
if unexpandedVars, ok := stringListScope[variable]; ok {
expandedVars := []string{}
for _, unexpandedVar := range unexpandedVars {
expandedVar, err := expandVarInternal(unexpandedVar, newSeenVars)
if err != nil {
return ret, err
}
expandedVars = append(expandedVars, expandedVar)
}
ret += strings.Join(expandedVars, " ")
} else if unexpandedVar, ok := stringScope[variable]; ok {
expandedVar, err := expandVarInternal(unexpandedVar, newSeenVars)
if err != nil {
return ret, err
}
ret += expandedVar
} else if unevaluatedVar, ok := exportedVars[variable]; ok {
evalFunc := reflect.ValueOf(unevaluatedVar)
validateVariableMethod(variable, evalFunc)
evaluatedResult := evalFunc.Call([]reflect.Value{reflect.ValueOf(config)})
evaluatedValue := evaluatedResult[0].Interface().(string)
expandedVar, err := expandVarInternal(evaluatedValue, newSeenVars)
if err != nil {
return ret, err
}
ret += expandedVar
} else {
return "", fmt.Errorf("Unbound config variable %s", variable)
}
}
return ret, nil
}
var ret []string
stringFields := splitStringKeepingQuotedSubstring(toExpand, ' ')
for _, v := range stringFields {
val, err := expandVarInternal(v, map[string]bool{})
if err != nil {
return ret, err
}
ret = append(ret, val)
}
return ret, nil
}
// splitStringKeepingQuotedSubstring splits a string on a provided separator,
// but it will not split substrings inside unescaped double quotes. If the double
// quotes are escaped, then the returned string will only include the quote, and
// not the escape.
func splitStringKeepingQuotedSubstring(s string, delimiter byte) []string {
var ret []string
quote := byte('"')
var substring []byte
quoted := false
escaped := false
for i := range s {
if !quoted && s[i] == delimiter {
ret = append(ret, string(substring))
substring = []byte{}
continue
}
characterIsEscape := i < len(s)-1 && s[i] == '\\' && s[i+1] == quote
if characterIsEscape {
escaped = true
continue
}
if s[i] == quote {
if !escaped {
quoted = !quoted
}
escaped = false
}
substring = append(substring, s[i])
}
ret = append(ret, string(substring))
return ret
}
func validateVariableMethod(name string, methodValue reflect.Value) {
methodType := methodValue.Type()
if methodType.Kind() != reflect.Func {
panic(fmt.Errorf("method given for variable %s is not a function",
name))
}
if n := methodType.NumIn(); n != 1 {
panic(fmt.Errorf("method for variable %s has %d inputs (should be 1)",
name, n))
}
if n := methodType.NumOut(); n != 1 {
panic(fmt.Errorf("method for variable %s has %d outputs (should be 1)",
name, n))
}
if kind := methodType.Out(0).Kind(); kind != reflect.String {
panic(fmt.Errorf("method for variable %s does not return a string",
name))
}
}