service,terminal,cmd/dlv: automatically guessing substitute-path config (#3781)

Add command, API calls and launch.json option to automatically guess
substitute-path configuration.

service/debugger/debugger.go

@@ -12,6 +12,7 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"path"
 	"path/filepath"
 	"regexp"
 	"runtime"
@@ -2551,3 +2552,157 @@ func (d *Debugger) maybePrintUnattendedBreakpointWarning(stopReason proc.StopRea
 	}
 	api.PrintStack(formatPathFunc, os.Stderr, apiFrames, "", false, api.StackTraceColors{}, includeFunc)
 }
+
+// GuessSubstitutePath returns a substitute-path configuration that maps
+// server paths to client paths by examining the executable file and a map
+// of module paths to client directories (clientMod2Dir) passed as input.
+func (d *Debugger) GuessSubstitutePath(args *api.GuessSubstitutePathIn) map[string]string {
+	bis := []*proc.BinaryInfo{}
+	bins := [][]proc.Function{}
+	tgt := proc.ValidTargets{Group: d.target}
+	for tgt.Next() {
+		bi := tgt.BinInfo()
+		bis = append(bis, bi)
+		bins = append(bins, bi.Functions)
+	}
+	return guessSubstitutePath(args, bins, func(biIdx int, fn *proc.Function) string {
+		file, _ := bis[biIdx].EntryLineForFunc(fn)
+		return file
+	})
+}
+
+func guessSubstitutePath(args *api.GuessSubstitutePathIn, bins [][]proc.Function, fileForFunc func(int, *proc.Function) string) map[string]string {
+	serverMod2Dir := map[string]string{}
+	serverMod2DirCandidate := map[string]map[string]int{}
+	pkg2mod := map[string]string{}
+
+	for mod := range args.ClientModuleDirectories {
+		serverMod2DirCandidate[mod] = make(map[string]int)
+	}
+
+	const minEvidence = 10
+	const decisionThreshold = 0.8
+
+	totCandidates := func(mod string) int {
+		r := 0
+		for _, cnt := range serverMod2DirCandidate[mod] {
+			r += cnt
+		}
+		return r
+	}
+
+	bestCandidate := func(mod string) string {
+		best := ""
+		for dir, cnt := range serverMod2DirCandidate[mod] {
+			if cnt > serverMod2DirCandidate[mod][best] {
+				best = dir
+			}
+		}
+		return best
+	}
+
+	slashes := func(s string) int {
+		r := 0
+		for _, ch := range s {
+			if ch == '/' {
+				r++
+			}
+		}
+		return r
+	}
+
+	serverGoroot := ""
+
+	logger := logflags.DebuggerLogger()
+
+	for binIdx, bin := range bins {
+		for i := range bin {
+			fn := &bin[i]
+
+			if fn.Name == "runtime.main" && serverGoroot == "" {
+				file := fileForFunc(binIdx, fn)
+				serverGoroot = path.Dir(path.Dir(path.Dir(file)))
+				continue
+			}
+
+			fnpkg := fn.PackageName()
+			if fn.CompilationUnitName() != "" && strings.ReplaceAll(fn.CompilationUnitName(), "\\", "/") != fnpkg {
+				// inlined
+				continue
+			}
+
+			if fnpkg == "main" && binIdx == 0 && args.ImportPathOfMainPackage != "" {
+				fnpkg = args.ImportPathOfMainPackage
+			}
+
+			fnmod := ""
+
+			if mod, ok := pkg2mod[fnpkg]; ok {
+				fnmod = mod
+			} else {
+				for mod := range args.ClientModuleDirectories {
+					if strings.HasPrefix(fnpkg, mod) {
+						fnmod = mod
+						break
+					}
+				}
+				pkg2mod[fnpkg] = fnmod
+				if fnmod == "" {
+					logger.Debugf("No module detected for server package %q", fnpkg)
+				}
+			}
+
+			if fnmod == "" {
+				// not in any module we are interested in
+				continue
+			}
+			if serverMod2Dir[fnmod] != "" {
+				// already decided
+				continue
+			}
+
+			elems := slashes(fnpkg[len(fnmod):])
+
+			file := fileForFunc(binIdx, fn)
+			if file == "" || file == "<autogenerated>" {
+				continue
+			}
+			logger.Debugf("considering %s pkg:%s compile unit:%s file:%s", fn.Name, fnpkg, fn.CompilationUnitName(), file)
+			dir := path.Dir(file) // note: paths are normalized to always use '/' as a separator by pkg/dwarf/line
+			if slashes(dir) < elems {
+				continue
+			}
+			for i := 0; i < elems; i++ {
+				dir = path.Dir(dir)
+			}
+
+			serverMod2DirCandidate[fnmod][dir]++
+
+			n := totCandidates(fnmod)
+			best := bestCandidate(fnmod)
+			if n > minEvidence && float64(serverMod2DirCandidate[fnmod][best])/float64(n) > decisionThreshold {
+				serverMod2Dir[fnmod] = best
+			}
+		}
+	}
+
+	for mod := range args.ClientModuleDirectories {
+		if serverMod2Dir[mod] == "" {
+			serverMod2Dir[mod] = bestCandidate(mod)
+		}
+	}
+
+	server2Client := make(map[string]string)
+
+	for mod, clientDir := range args.ClientModuleDirectories {
+		if serverMod2Dir[mod] != "" {
+			server2Client[serverMod2Dir[mod]] = clientDir
+		}
+	}
+
+	if serverGoroot != "" && args.ClientGOROOT != "" {
+		server2Client[serverGoroot] = args.ClientGOROOT
+	}
+
+	return server2Client
+}