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net/http: pattern.conflictsWith
Add the conflictsWith method, which determines whether two patterns conflict with each other. Updates #61410. Change-Id: Id4f9a471dc9d0420d927a68d2864128a096b74f4 Reviewed-on: https://go-review.googlesource.com/c/go/+/526616 Run-TryBot: Jonathan Amsterdam <jba@google.com> Reviewed-by: Eli Bendersky <eliben@google.com> Reviewed-by: Damien Neil <dneil@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Jonathan Amsterdam
parent
4f9fe6d509
commit
3602465954
@ -33,6 +33,12 @@ type pattern struct {
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loc string // source location of registering call, for helpful messages
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}
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func (p *pattern) String() string { return p.str }
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func (p *pattern) lastSegment() segment {
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return p.segments[len(p.segments)-1]
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}
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// A segment is a pattern piece that matches one or more path segments, or
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// a trailing slash.
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//
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@ -185,3 +191,185 @@ func isValidWildcardName(s string) bool {
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}
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return true
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}
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// relationship is a relationship between two patterns, p1 and p2.
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type relationship string
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const (
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equivalent relationship = "equivalent" // both match the same requests
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moreGeneral relationship = "moreGeneral" // p1 matches everything p2 does & more
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moreSpecific relationship = "moreSpecific" // p2 matches everything p1 does & more
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disjoint relationship = "disjoint" // there is no request that both match
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overlaps relationship = "overlaps" // there is a request that both match, but neither is more specific
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)
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// conflictsWith reports whether p1 conflicts with p2, that is, whether
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// there is a request that both match but where neither is higher precedence
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// than the other.
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//
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// Precedence is defined by two rules:
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// 1. Patterns with a host win over patterns without a host.
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// 2. Patterns whose method and path is more specific win. One pattern is more
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// specific than another if the second matches all the (method, path) pairs
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// of the first and more.
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//
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// If rule 1 doesn't apply, then two patterns conflict if their relationship
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// is either equivalence (they match the same set of requests) or overlap
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// (they both match some requests, but neither is more specific than the other).
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func (p1 *pattern) conflictsWith(p2 *pattern) bool {
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if p1.host != p2.host {
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// Either one host is empty and the other isn't, in which case the
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// one with the host wins by rule 1, or neither host is empty
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// and they differ, so they won't match the same paths.
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return false
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}
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rel := p1.comparePathsAndMethods(p2)
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return rel == equivalent || rel == overlaps
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}
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func (p1 *pattern) comparePathsAndMethods(p2 *pattern) relationship {
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mrel := p1.compareMethods(p2)
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// Optimization: avoid a call to comparePaths.
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if mrel == disjoint {
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return disjoint
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}
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prel := p1.comparePaths(p2)
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return combineRelationships(mrel, prel)
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}
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// compareMethods determines the relationship between the method
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// part of patterns p1 and p2.
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//
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// A method can either be empty, "GET", or something else.
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// The empty string matches any method, so it is the most general.
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// "GET" matches both GET and HEAD.
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// Anything else matches only itself.
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func (p1 *pattern) compareMethods(p2 *pattern) relationship {
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if p1.method == p2.method {
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return equivalent
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}
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if p1.method == "" {
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// p1 matches any method, but p2 does not, so p1 is more general.
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return moreGeneral
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}
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if p2.method == "" {
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return moreSpecific
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}
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if p1.method == "GET" && p2.method == "HEAD" {
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// p1 matches GET and HEAD; p2 matches only HEAD.
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return moreGeneral
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}
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if p2.method == "GET" && p1.method == "HEAD" {
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return moreSpecific
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}
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return disjoint
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}
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// comparePaths determines the relationship between the path
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// part of two patterns.
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func (p1 *pattern) comparePaths(p2 *pattern) relationship {
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// Optimization: if a path pattern doesn't end in a multi ("...") wildcard, then it
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// can only match paths with the same number of segments.
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if len(p1.segments) != len(p2.segments) && !p1.lastSegment().multi && !p2.lastSegment().multi {
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return disjoint
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}
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var segs1, segs2 []segment
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// Look at corresponding segments in the two path patterns.
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rel := equivalent
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for segs1, segs2 = p1.segments, p2.segments; len(segs1) > 0 && len(segs2) > 0; segs1, segs2 = segs1[1:], segs2[1:] {
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rel = combineRelationships(rel, compareSegments(segs1[0], segs2[0]))
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if rel == disjoint || rel == overlaps {
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return rel
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}
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}
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// We've reached the end of the corresponding segments of the patterns.
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// If they have the same number of segments, then we've already determined
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// their relationship.
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if len(segs1) == 0 && len(segs2) == 0 {
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return rel
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}
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// Otherwise, the only way they could fail to be disjoint is if the shorter
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// pattern ends in a multi and is more general.
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if len(segs1) < len(segs2) && p1.lastSegment().multi && rel == moreGeneral {
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return moreGeneral
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}
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if len(segs2) < len(segs1) && p2.lastSegment().multi && rel == moreSpecific {
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return moreSpecific
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}
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return disjoint
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}
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// compareSegments determines the relationship between two segments.
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func compareSegments(s1, s2 segment) relationship {
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if s1.multi && s2.multi {
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return equivalent
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}
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if s1.multi {
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return moreGeneral
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}
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if s2.multi {
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return moreSpecific
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}
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if s1.wild && s2.wild {
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return equivalent
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}
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if s1.wild {
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if s2.s == "/" {
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// A single wildcard doesn't match a trailing slash.
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return disjoint
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}
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return moreGeneral
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}
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if s2.wild {
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if s1.s == "/" {
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return disjoint
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}
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return moreSpecific
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}
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// Both literals.
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if s1.s == s2.s {
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return equivalent
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}
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return disjoint
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}
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// combineRelationships determines the overall relationship of two patterns
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// given the relationships of a partition of the patterns into two parts.
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//
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// For example, if p1 is more general than p2 in one way but equivalent
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// in the other, then it is more general overall.
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//
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// Or if p1 is more general in one way and more specific in the other, then
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// they overlap.
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func combineRelationships(r1, r2 relationship) relationship {
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switch r1 {
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case equivalent:
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return r2
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case disjoint, overlaps:
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return r1
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case moreGeneral, moreSpecific:
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switch r2 {
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case equivalent:
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return r1
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case inverseRelationship(r1):
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return overlaps
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default:
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return r2
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}
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default:
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panic(fmt.Sprintf("unknown relationship %q", r1))
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}
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}
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// If p1 has relationship `r` to p2, then
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// p2 has inverseRelationship(r) to p1.
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func inverseRelationship(r relationship) relationship {
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switch r {
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case moreSpecific:
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return moreGeneral
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case moreGeneral:
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return moreSpecific
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default:
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return r
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}
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}
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@ -165,3 +165,227 @@ func mustParsePattern(t *testing.T, s string) *pattern {
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}
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return p
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}
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func TestCompareMethods(t *testing.T) {
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for _, test := range []struct {
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p1, p2 string
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want relationship
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}{
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{"/", "/", equivalent},
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{"GET /", "GET /", equivalent},
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{"HEAD /", "HEAD /", equivalent},
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{"POST /", "POST /", equivalent},
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{"GET /", "POST /", disjoint},
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{"GET /", "/", moreSpecific},
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{"HEAD /", "/", moreSpecific},
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{"GET /", "HEAD /", moreGeneral},
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} {
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pat1 := mustParsePattern(t, test.p1)
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pat2 := mustParsePattern(t, test.p2)
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got := pat1.compareMethods(pat2)
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if got != test.want {
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t.Errorf("%s vs %s: got %s, want %s", test.p1, test.p2, got, test.want)
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}
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got2 := pat2.compareMethods(pat1)
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want2 := inverseRelationship(test.want)
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if got2 != want2 {
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t.Errorf("%s vs %s: got %s, want %s", test.p2, test.p1, got2, want2)
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}
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}
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}
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func TestComparePaths(t *testing.T) {
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for _, test := range []struct {
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p1, p2 string
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want relationship
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}{
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// A non-final pattern segment can have one of two values: literal or
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// single wildcard. A final pattern segment can have one of 5: empty
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// (trailing slash), literal, dollar, single wildcard, or multi
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// wildcard. Trailing slash and multi wildcard are the same.
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// A literal should be more specific than anything it overlaps, except itself.
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{"/a", "/a", equivalent},
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{"/a", "/b", disjoint},
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{"/a", "/", moreSpecific},
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{"/a", "/{$}", disjoint},
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{"/a", "/{x}", moreSpecific},
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{"/a", "/{x...}", moreSpecific},
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// Adding a segment doesn't change that.
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{"/b/a", "/b/a", equivalent},
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{"/b/a", "/b/b", disjoint},
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{"/b/a", "/b/", moreSpecific},
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{"/b/a", "/b/{$}", disjoint},
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{"/b/a", "/b/{x}", moreSpecific},
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{"/b/a", "/b/{x...}", moreSpecific},
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{"/{z}/a", "/{z}/a", equivalent},
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{"/{z}/a", "/{z}/b", disjoint},
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{"/{z}/a", "/{z}/", moreSpecific},
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{"/{z}/a", "/{z}/{$}", disjoint},
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{"/{z}/a", "/{z}/{x}", moreSpecific},
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{"/{z}/a", "/{z}/{x...}", moreSpecific},
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// Single wildcard on left.
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{"/{z}", "/a", moreGeneral},
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{"/{z}", "/a/b", disjoint},
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{"/{z}", "/{$}", disjoint},
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{"/{z}", "/{x}", equivalent},
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{"/{z}", "/", moreSpecific},
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{"/{z}", "/{x...}", moreSpecific},
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{"/b/{z}", "/b/a", moreGeneral},
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{"/b/{z}", "/b/a/b", disjoint},
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{"/b/{z}", "/b/{$}", disjoint},
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{"/b/{z}", "/b/{x}", equivalent},
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{"/b/{z}", "/b/", moreSpecific},
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{"/b/{z}", "/b/{x...}", moreSpecific},
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// Trailing slash on left.
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{"/", "/a", moreGeneral},
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{"/", "/a/b", moreGeneral},
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{"/", "/{$}", moreGeneral},
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{"/", "/{x}", moreGeneral},
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{"/", "/", equivalent},
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{"/", "/{x...}", equivalent},
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{"/b/", "/b/a", moreGeneral},
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{"/b/", "/b/a/b", moreGeneral},
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{"/b/", "/b/{$}", moreGeneral},
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{"/b/", "/b/{x}", moreGeneral},
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{"/b/", "/b/", equivalent},
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{"/b/", "/b/{x...}", equivalent},
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{"/{z}/", "/{z}/a", moreGeneral},
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{"/{z}/", "/{z}/a/b", moreGeneral},
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{"/{z}/", "/{z}/{$}", moreGeneral},
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{"/{z}/", "/{z}/{x}", moreGeneral},
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{"/{z}/", "/{z}/", equivalent},
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{"/{z}/", "/a/", moreGeneral},
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{"/{z}/", "/{z}/{x...}", equivalent},
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{"/{z}/", "/a/{x...}", moreGeneral},
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{"/a/{z}/", "/{z}/a/", overlaps},
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{"/a/{z}/b/", "/{x}/c/{y...}", overlaps},
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// Multi wildcard on left.
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{"/{m...}", "/a", moreGeneral},
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{"/{m...}", "/a/b", moreGeneral},
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{"/{m...}", "/{$}", moreGeneral},
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{"/{m...}", "/{x}", moreGeneral},
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{"/{m...}", "/", equivalent},
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{"/{m...}", "/{x...}", equivalent},
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{"/b/{m...}", "/b/a", moreGeneral},
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{"/b/{m...}", "/b/a/b", moreGeneral},
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{"/b/{m...}", "/b/{$}", moreGeneral},
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{"/b/{m...}", "/b/{x}", moreGeneral},
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{"/b/{m...}", "/b/", equivalent},
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{"/b/{m...}", "/b/{x...}", equivalent},
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{"/b/{m...}", "/a/{x...}", disjoint},
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{"/{z}/{m...}", "/{z}/a", moreGeneral},
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{"/{z}/{m...}", "/{z}/a/b", moreGeneral},
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{"/{z}/{m...}", "/{z}/{$}", moreGeneral},
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{"/{z}/{m...}", "/{z}/{x}", moreGeneral},
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{"/{z}/{m...}", "/{w}/", equivalent},
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{"/{z}/{m...}", "/a/", moreGeneral},
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{"/{z}/{m...}", "/{z}/{x...}", equivalent},
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{"/{z}/{m...}", "/a/{x...}", moreGeneral},
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{"/a/{m...}", "/a/b/{y...}", moreGeneral},
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{"/a/{m...}", "/a/{x}/{y...}", moreGeneral},
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{"/a/{z}/{m...}", "/a/b/{y...}", moreGeneral},
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{"/a/{z}/{m...}", "/{z}/a/", overlaps},
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{"/a/{z}/{m...}", "/{z}/b/{y...}", overlaps},
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{"/a/{z}/b/{m...}", "/{x}/c/{y...}", overlaps},
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// Dollar on left.
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{"/{$}", "/a", disjoint},
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{"/{$}", "/a/b", disjoint},
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{"/{$}", "/{$}", equivalent},
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{"/{$}", "/{x}", disjoint},
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{"/{$}", "/", moreSpecific},
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{"/{$}", "/{x...}", moreSpecific},
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{"/b/{$}", "/b", disjoint},
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{"/b/{$}", "/b/a", disjoint},
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{"/b/{$}", "/b/a/b", disjoint},
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{"/b/{$}", "/b/{$}", equivalent},
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{"/b/{$}", "/b/{x}", disjoint},
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{"/b/{$}", "/b/", moreSpecific},
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{"/b/{$}", "/b/{x...}", moreSpecific},
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{"/b/{$}", "/b/c/{x...}", disjoint},
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{"/b/{x}/a/{$}", "/{x}/c/{y...}", overlaps},
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{"/{z}/{$}", "/{z}/a", disjoint},
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{"/{z}/{$}", "/{z}/a/b", disjoint},
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{"/{z}/{$}", "/{z}/{$}", equivalent},
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{"/{z}/{$}", "/{z}/{x}", disjoint},
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{"/{z}/{$}", "/{z}/", moreSpecific},
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{"/{z}/{$}", "/a/", overlaps},
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{"/{z}/{$}", "/a/{x...}", overlaps},
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{"/{z}/{$}", "/{z}/{x...}", moreSpecific},
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{"/a/{z}/{$}", "/{z}/a/", overlaps},
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} {
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pat1 := mustParsePattern(t, test.p1)
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pat2 := mustParsePattern(t, test.p2)
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if g := pat1.comparePaths(pat1); g != equivalent {
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t.Errorf("%s does not match itself; got %s", pat1, g)
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}
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if g := pat2.comparePaths(pat2); g != equivalent {
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t.Errorf("%s does not match itself; got %s", pat2, g)
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}
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got := pat1.comparePaths(pat2)
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if got != test.want {
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t.Errorf("%s vs %s: got %s, want %s", test.p1, test.p2, got, test.want)
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t.Logf("pat1: %+v\n", pat1.segments)
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t.Logf("pat2: %+v\n", pat2.segments)
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}
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want2 := inverseRelationship(test.want)
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got2 := pat2.comparePaths(pat1)
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if got2 != want2 {
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t.Errorf("%s vs %s: got %s, want %s", test.p2, test.p1, got2, want2)
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}
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}
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}
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func TestConflictsWith(t *testing.T) {
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for _, test := range []struct {
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p1, p2 string
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want bool
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}{
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{"/a", "/a", true},
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{"/a", "/ab", false},
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{"/a/b/cd", "/a/b/cd", true},
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{"/a/b/cd", "/a/b/c", false},
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{"/a/b/c", "/a/c/c", false},
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{"/{x}", "/{y}", true},
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{"/{x}", "/a", false}, // more specific
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{"/{x}/{y}", "/{x}/a", false},
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{"/{x}/{y}", "/{x}/a/b", false},
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{"/{x}", "/a/{y}", false},
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{"/{x}/{y}", "/{x}/a/", false},
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{"/{x}", "/a/{y...}", false}, // more specific
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{"/{x}/a/{y}", "/{x}/a/{y...}", false}, // more specific
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{"/{x}/{y}", "/{x}/a/{$}", false}, // more specific
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{"/{x}/{y}/{$}", "/{x}/a/{$}", false},
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{"/a/{x}", "/{x}/b", true},
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{"/", "GET /", false},
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{"/", "GET /foo", false},
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{"GET /", "GET /foo", false},
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{"GET /", "/foo", true},
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{"GET /foo", "HEAD /", true},
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} {
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pat1 := mustParsePattern(t, test.p1)
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pat2 := mustParsePattern(t, test.p2)
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got := pat1.conflictsWith(pat2)
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if got != test.want {
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t.Errorf("%q.ConflictsWith(%q) = %t, want %t",
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test.p1, test.p2, got, test.want)
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}
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// conflictsWith should be commutative.
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got = pat2.conflictsWith(pat1)
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if got != test.want {
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t.Errorf("%q.ConflictsWith(%q) = %t, want %t",
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test.p2, test.p1, got, test.want)
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}
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}
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}
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