mirror of
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go/build, internal/dag: lift DAG parser into an internal package
This lifts the DAG parser from the go/build dependencies test into its own package that can be reused elsewhere. I tried to keep the code as close as possible. I changed some names to reflect the more general purpose of internal/dag. Most of the changes are related to error handling, since internal/dag doesn't take a testing.T on which to report errors. Notably, parseRules now returns a slice of parsed rules rather than calling a callback because this made it easier to separate fatal parsing errors from non-fatal graph checking errors. For #53789. Change-Id: I170b84fd85f971cfc1a50972156d48e78b45fce3 Reviewed-on: https://go-review.googlesource.com/c/go/+/418592 Reviewed-by: Michael Pratt <mpratt@google.com> Run-TryBot: Austin Clements <austin@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Austin Clements
parent
ab0a94c6d3
commit
d37cc9a8cd
@ -11,6 +11,7 @@ import (
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"bytes"
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"fmt"
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"go/token"
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"internal/dag"
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"internal/testenv"
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"io/fs"
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"os"
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@ -29,40 +30,9 @@ import (
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// without prior discussion.
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// Negative assertions should almost never be removed.
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//
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// The general syntax of a rule is:
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// "a < b" means package b can import package a.
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//
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// a, b < c, d;
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//
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// which means c and d come after a and b in the partial order
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// (that is, c and d can import a and b),
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// but doesn't provide a relative order between a vs b or c vs d.
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//
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// The rules can chain together, as in:
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//
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// e < f, g < h;
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//
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// which is equivalent to
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//
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// e < f, g;
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// f, g < h;
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//
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// Except for the special bottom element "NONE", each name
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// must appear exactly once on the right-hand side of a rule.
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// That rule serves as the definition of the allowed dependencies
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// for that name. The definition must appear before any uses
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// of the name on the left-hand side of a rule. (That is, the
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// rules themselves must be ordered according to the partial
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// order, for easier reading by people.)
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//
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// Negative assertions double-check the partial order:
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//
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// i !< j
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//
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// means that it must NOT be the case that i < j.
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// Negative assertions may appear anywhere in the rules,
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// even before i and j have been defined.
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//
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// Comments begin with #.
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// See `go doc internal/dag' for the full syntax.
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//
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// All-caps names are pseudo-names for specific points
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// in the dependency lattice.
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@ -208,6 +178,7 @@ var depsRules = `
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# Misc packages needing only FMT.
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FMT
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< html,
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internal/dag,
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internal/goroot,
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mime/quotedprintable,
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net/internal/socktest,
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@ -700,186 +671,11 @@ func findImports(pkg string) ([]string, error) {
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// depsPolicy returns a map m such that m[p][d] == true when p can import d.
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func depsPolicy(t *testing.T) map[string]map[string]bool {
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allowed := map[string]map[string]bool{"NONE": {}}
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disallowed := [][2][]string{}
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parseDepsRules(t, func(deps []string, op string, users []string) {
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if op == "!<" {
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disallowed = append(disallowed, [2][]string{deps, users})
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return
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}
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for _, u := range users {
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if allowed[u] != nil {
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t.Errorf("multiple deps lists for %s", u)
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}
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allowed[u] = make(map[string]bool)
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for _, d := range deps {
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if allowed[d] == nil {
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t.Errorf("use of %s before its deps list", d)
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}
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allowed[u][d] = true
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}
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}
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})
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// Check for missing deps info.
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for _, deps := range allowed {
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for d := range deps {
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if allowed[d] == nil {
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t.Errorf("missing deps list for %s", d)
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}
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}
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}
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// Complete transitive allowed deps.
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for k := range allowed {
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for i := range allowed {
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for j := range allowed {
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if i != k && k != j && allowed[i][k] && allowed[k][j] {
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if i == j {
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// Can only happen along with a "use of X before deps" error above,
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// but this error is more specific - it makes clear that reordering the
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// rules will not be enough to fix the problem.
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t.Errorf("deps policy cycle: %s < %s < %s", j, k, i)
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}
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allowed[i][j] = true
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}
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}
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}
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}
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// Check negative assertions against completed allowed deps.
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for _, bad := range disallowed {
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deps, users := bad[0], bad[1]
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for _, d := range deps {
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for _, u := range users {
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if allowed[u][d] {
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t.Errorf("deps policy incorrect: assertion failed: %s !< %s", d, u)
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}
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}
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}
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}
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if t.Failed() {
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t.FailNow()
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}
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return allowed
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}
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// parseDepsRules parses depsRules, calling save(deps, op, users)
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// for each deps < users or deps !< users rule
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// (op is "<" or "!<").
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func parseDepsRules(t *testing.T, save func(deps []string, op string, users []string)) {
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p := &depsParser{t: t, lineno: 1, text: depsRules}
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var prev []string
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var op string
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for {
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list, tok := p.nextList()
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if tok == "" {
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if prev == nil {
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break
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}
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p.syntaxError("unexpected EOF")
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}
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if prev != nil {
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save(prev, op, list)
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}
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prev = list
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if tok == ";" {
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prev = nil
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op = ""
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continue
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}
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if tok != "<" && tok != "!<" {
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p.syntaxError("missing <")
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}
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op = tok
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}
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}
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// A depsParser parses the depsRules syntax described above.
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type depsParser struct {
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t *testing.T
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lineno int
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lastWord string
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text string
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}
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// syntaxError reports a parsing error.
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func (p *depsParser) syntaxError(msg string) {
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p.t.Fatalf("deps:%d: syntax error: %s near %s", p.lineno, msg, p.lastWord)
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}
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// nextList parses and returns a comma-separated list of names.
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func (p *depsParser) nextList() (list []string, token string) {
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for {
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tok := p.nextToken()
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switch tok {
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case "":
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if len(list) == 0 {
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return nil, ""
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}
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fallthrough
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case ",", "<", "!<", ";":
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p.syntaxError("bad list syntax")
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}
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list = append(list, tok)
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tok = p.nextToken()
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if tok != "," {
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return list, tok
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}
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}
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}
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// nextToken returns the next token in the deps rules,
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// one of ";" "," "<" "!<" or a name.
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func (p *depsParser) nextToken() string {
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for {
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if p.text == "" {
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return ""
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}
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switch p.text[0] {
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case ';', ',', '<':
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t := p.text[:1]
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p.text = p.text[1:]
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return t
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case '!':
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if len(p.text) < 2 || p.text[1] != '<' {
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p.syntaxError("unexpected token !")
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}
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p.text = p.text[2:]
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return "!<"
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case '#':
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i := strings.Index(p.text, "\n")
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if i < 0 {
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i = len(p.text)
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}
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p.text = p.text[i:]
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continue
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case '\n':
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p.lineno++
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fallthrough
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case ' ', '\t':
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p.text = p.text[1:]
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continue
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default:
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i := strings.IndexAny(p.text, "!;,<#\n \t")
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if i < 0 {
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i = len(p.text)
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}
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t := p.text[:i]
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p.text = p.text[i:]
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p.lastWord = t
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return t
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}
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g, err := dag.Parse(depsRules)
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if err != nil {
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t.Fatal(err)
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}
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return g
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}
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// TestStdlibLowercase tests that all standard library package names are
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264
src/internal/dag/parse.go
Normal file
264
src/internal/dag/parse.go
Normal file
@ -0,0 +1,264 @@
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// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package dag implements a language for expressing directed acyclic
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// graphs.
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//
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// The general syntax of a rule is:
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//
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// a, b < c, d;
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//
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// which means c and d come after a and b in the partial order
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// (that is, there are edges from c and d to a and b),
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// but doesn't provide a relative order between a vs b or c vs d.
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//
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// The rules can chain together, as in:
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//
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// e < f, g < h;
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//
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// which is equivalent to
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//
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// e < f, g;
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// f, g < h;
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//
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// Except for the special bottom element "NONE", each name
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// must appear exactly once on the right-hand side of any rule.
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// That rule serves as the definition of the allowed successor
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// for that name. The definition must appear before any uses
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// of the name on the left-hand side of a rule. (That is, the
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// rules themselves must be ordered according to the partial
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// order, for easier reading by people.)
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//
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// Negative assertions double-check the partial order:
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//
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// i !< j
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//
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// means that it must NOT be the case that i < j.
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// Negative assertions may appear anywhere in the rules,
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// even before i and j have been defined.
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//
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// Comments begin with #.
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package dag
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import (
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"fmt"
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"strings"
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)
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// Parse returns a map m such that m[p][d] == true when there is a
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// path from p to d.
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func Parse(dag string) (map[string]map[string]bool, error) {
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allowed := map[string]map[string]bool{"NONE": {}}
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disallowed := []rule{}
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rules, err := parseRules(dag)
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if err != nil {
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return nil, err
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}
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// TODO: Add line numbers to errors.
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var errors []string
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errorf := func(format string, a ...any) {
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errors = append(errors, fmt.Sprintf(format, a...))
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}
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for _, r := range rules {
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if r.op == "!<" {
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disallowed = append(disallowed, r)
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continue
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}
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for _, def := range r.def {
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if allowed[def] != nil {
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errorf("multiple definitions for %s", def)
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}
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allowed[def] = make(map[string]bool)
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for _, less := range r.less {
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if allowed[less] == nil {
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errorf("use of %s before its definition", less)
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}
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allowed[def][less] = true
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}
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}
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}
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// Check for missing definition.
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for _, tos := range allowed {
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for to := range tos {
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if allowed[to] == nil {
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errorf("missing definition for %s", to)
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}
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}
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}
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// Complete transitive closure.
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for k := range allowed {
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for i := range allowed {
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for j := range allowed {
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if i != k && k != j && allowed[i][k] && allowed[k][j] {
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if i == j {
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// Can only happen along with a "use of X before deps" error above,
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// but this error is more specific - it makes clear that reordering the
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// rules will not be enough to fix the problem.
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errorf("graph cycle: %s < %s < %s", j, k, i)
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}
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allowed[i][j] = true
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}
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}
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}
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}
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// Check negative assertions against completed allowed graph.
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for _, bad := range disallowed {
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for _, less := range bad.less {
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for _, def := range bad.def {
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if allowed[def][less] {
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errorf("graph edge assertion failed: %s !< %s", less, def)
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}
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}
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}
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}
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if len(errors) > 0 {
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return nil, fmt.Errorf("%s", strings.Join(errors, "\n"))
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}
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return allowed, nil
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}
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// A rule is a line in the DAG language where "less < def" or "less !< def".
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type rule struct {
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less []string
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op string // Either "<" or "!<"
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def []string
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}
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type syntaxError string
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func (e syntaxError) Error() string {
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return string(e)
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}
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// parseRules parses the rules of a DAG.
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func parseRules(rules string) (out []rule, err error) {
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defer func() {
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e := recover()
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switch e := e.(type) {
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case nil:
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return
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case syntaxError:
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err = e
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default:
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panic(e)
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}
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}()
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p := &rulesParser{lineno: 1, text: rules}
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var prev []string
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var op string
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for {
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list, tok := p.nextList()
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if tok == "" {
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if prev == nil {
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break
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}
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p.syntaxError("unexpected EOF")
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}
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if prev != nil {
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out = append(out, rule{prev, op, list})
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}
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prev = list
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if tok == ";" {
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prev = nil
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op = ""
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continue
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}
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if tok != "<" && tok != "!<" {
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p.syntaxError("missing <")
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}
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op = tok
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}
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return out, err
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}
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// A rulesParser parses the depsRules syntax described above.
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type rulesParser struct {
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lineno int
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lastWord string
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text string
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}
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// syntaxError reports a parsing error.
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func (p *rulesParser) syntaxError(msg string) {
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panic(syntaxError(fmt.Sprintf("parsing graph: line %d: syntax error: %s near %s", p.lineno, msg, p.lastWord)))
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}
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// nextList parses and returns a comma-separated list of names.
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func (p *rulesParser) nextList() (list []string, token string) {
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for {
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tok := p.nextToken()
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switch tok {
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case "":
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if len(list) == 0 {
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return nil, ""
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}
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fallthrough
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case ",", "<", "!<", ";":
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p.syntaxError("bad list syntax")
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}
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list = append(list, tok)
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tok = p.nextToken()
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if tok != "," {
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return list, tok
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}
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}
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}
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// nextToken returns the next token in the deps rules,
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// one of ";" "," "<" "!<" or a name.
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func (p *rulesParser) nextToken() string {
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for {
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if p.text == "" {
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return ""
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}
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switch p.text[0] {
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case ';', ',', '<':
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t := p.text[:1]
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p.text = p.text[1:]
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return t
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case '!':
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if len(p.text) < 2 || p.text[1] != '<' {
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p.syntaxError("unexpected token !")
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}
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p.text = p.text[2:]
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return "!<"
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case '#':
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i := strings.Index(p.text, "\n")
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if i < 0 {
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i = len(p.text)
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}
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p.text = p.text[i:]
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continue
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case '\n':
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p.lineno++
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fallthrough
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case ' ', '\t':
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p.text = p.text[1:]
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continue
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default:
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i := strings.IndexAny(p.text, "!;,<#\n \t")
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if i < 0 {
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i = len(p.text)
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}
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t := p.text[:i]
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p.text = p.text[i:]
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p.lastWord = t
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return t
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}
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}
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}
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