@@ -55,6 +55,129 @@ class PackageGraphNode {
5555 satisfies ( { gitCommittish, gitRange, fetchSpec } ) {
5656 return semver . satisfies ( this . version , gitCommittish || gitRange || fetchSpec ) ;
5757 }
58+
59+ /**
60+ * Returns a string representation of this node (its name)
61+ *
62+ * @returns {String }
63+ */
64+ toString ( ) {
65+ return this . name ;
66+ }
67+ }
68+
69+ let lastCollapsedNodeId = 0 ;
70+
71+ /**
72+ * Represents a cyclic collection of nodes in a PackageGraph.
73+ * It is meant to be used as a black box, where the only exposed
74+ * information are the connections to the other nodes of the graph.
75+ * It can contains either `PackageGraphNode`s or other `CyclicPackageGraphNode`s.
76+ */
77+ class CyclicPackageGraphNode extends Map {
78+ constructor ( ) {
79+ super ( ) ;
80+
81+ this . localDependencies = new Map ( ) ;
82+ this . localDependents = new Map ( ) ;
83+
84+ Object . defineProperties ( this , {
85+ // immutable properties
86+ name : {
87+ enumerable : true ,
88+ value : `(cycle) ${ ( lastCollapsedNodeId += 1 ) } ,
89+ } ,
90+ isCycle : {
91+ value : true ,
92+ } ,
93+ } ) ;
94+ }
95+
96+ /**
97+ * @returns {String } Returns a representation of a cycle, like like `A -> B -> C -> A`.
98+ */
99+ toString ( ) {
100+ const parts = Array . from ( this , ( [ key , node ] ) =>
101+ node . isCycle ? `(nested cycle: ${ node . toString ( ) } : key
102+ ) ;
103+
104+ // start from the origin
105+ parts . push ( parts [ 0 ] ) ;
106+
107+ return parts . reverse ( ) . join ( " -> " ) ;
108+ }
109+
110+ /**
111+ * Flattens a CyclicPackageGraphNode (which can have multiple level of cycles).
112+ *
113+ * @returns {PackageGraphNode[] }
114+ */
115+ flatten ( ) {
116+ const result = [ ] ;
117+
118+ for ( const node of this . values ( ) ) {
119+ if ( node . isCycle ) {
120+ result . push ( ...node . flatten ( ) ) ;
121+ } else {
122+ result . push ( node ) ;
123+ }
124+ }
125+
126+ return result ;
127+ }
128+
129+ /**
130+ * Checks if a given node is contained in this cycle (or in a nested one)
131+ *
132+ * @param {String } name The name of the package to search in this cycle
133+ * @returns {Boolean }
134+ */
135+ contains ( name ) {
136+ for ( const [ currentName , currentNode ] of this ) {
137+ if ( currentNode . isCycle ) {
138+ if ( currentNode . contains ( name ) ) {
139+ return true ;
140+ }
141+ } else if ( currentName === name ) {
142+ return true ;
143+ }
144+ }
145+ return false ;
146+ }
147+
148+ /**
149+ * Adds a graph node, or a nested cycle, to this group.
150+ *
151+ * @param {PackageGraphNode|CyclicPackageGraphNode } node
152+ */
153+ insert ( node ) {
154+ this . set ( node . name , node ) ;
155+ this . unlink ( node ) ;
156+
157+ for ( const [ dependencyName , dependencyNode ] of node . localDependencies ) {
158+ if ( ! this . contains ( dependencyName ) ) {
159+ this . localDependencies . set ( dependencyName , dependencyNode ) ;
160+ }
161+ }
162+
163+ for ( const [ dependentName , dependentNode ] of node . localDependents ) {
164+ if ( ! this . contains ( dependentName ) ) {
165+ this . localDependents . set ( dependentName , dependentNode ) ;
166+ }
167+ }
168+ }
169+
170+ /**
171+ * Remove pointers to candidate node from internal collections.
172+ * @param {PackageGraphNode|CyclicPackageGraphNode } candidateNode instance to unlink
173+ */
174+ unlink ( candidateNode ) {
175+ // remove incoming edges ("indegree")
176+ this . localDependencies . delete ( candidateNode . name ) ;
177+
178+ // remove outgoing edges ("outdegree")
179+ this . localDependents . delete ( candidateNode . name ) ;
180+ }
58181}
59182
60183/**
@@ -190,7 +313,10 @@ class PackageGraph extends Map {
190313 }
191314
192315 /**
193- * Return a tuple of cycle paths and nodes, which have been removed from the graph.
316+ * Return a tuple of cycle paths and nodes.
317+ *
318+ * @deprecated Use collapseCycles instead.
319+ *
194320 * @param {!boolean } rejectCycles Whether or not to reject cycles
195321 * @returns [Set<String[]>, Set<PackageGraphNode>]
196322 */
@@ -238,19 +364,71 @@ class PackageGraph extends Map {
238364 currentNode . localDependents . forEach ( visits ( [ currentName ] ) ) ;
239365 } ) ;
240366
241- if ( cyclePaths . size ) {
242- const cycleMessage = [ "Dependency cycles detected, you should fix these!" ]
243- . concat ( Array . from ( cyclePaths ) . map ( cycle => cycle . join ( " -> " ) ) )
244- . join ( "\n" ) ;
367+ reportCycles ( Array . from ( cyclePaths , cycle => cycle . join ( " -> " ) ) , rejectCycles ) ;
245368
246- if ( rejectCycles ) {
247- throw new ValidationError ( "ECYCLE" , cycleMessage ) ;
369+ return [ cyclePaths , cycleNodes ] ;
370+ }
371+
372+ /**
373+ * Returns the cycles of this graph. If two cycles share some elements, they will
374+ * be returned as a single cycle.
375+ *
376+ * @param {!boolean } rejectCycles Whether or not to reject cycles
377+ * @returns Set<CyclicPackageGraphNode>
378+ */
379+ collapseCycles ( rejectCycles ) {
380+ const cyclePaths = [ ] ;
381+ const nodeToCycle = new Map ( ) ;
382+ const cycles = new Set ( ) ;
383+
384+ const walkStack = [ ] ;
385+
386+ function visits ( baseNode , dependentNode ) {
387+ if ( nodeToCycle . has ( baseNode ) ) {
388+ return ;
389+ }
390+
391+ let topLevelDependent = dependentNode ;
392+ while ( nodeToCycle . has ( topLevelDependent ) ) {
393+ topLevelDependent = nodeToCycle . get ( topLevelDependent ) ;
394+ }
395+
396+ if (
397+ topLevelDependent === baseNode ||
398+ ( topLevelDependent . isCycle && topLevelDependent . has ( baseNode . name ) )
399+ ) {
400+ const cycle = new CyclicPackageGraphNode ( ) ;
401+
402+ walkStack . forEach ( nodeInCycle => {
403+ nodeToCycle . set ( nodeInCycle , cycle ) ;
404+ cycle . insert ( nodeInCycle ) ;
405+ cycles . delete ( nodeInCycle ) ;
406+ } ) ;
407+
408+ cycles . add ( cycle ) ;
409+ cyclePaths . push ( cycle . toString ( ) ) ;
410+
411+ return ;
248412 }
249413
250- log . warn ( "ECYCLE" , cycleMessage ) ;
414+ if ( walkStack . indexOf ( topLevelDependent ) === - 1 ) {
415+ // eslint-disable-next-line no-use-before-define
416+ visitWithStack ( baseNode , topLevelDependent ) ;
417+ }
251418 }
252419
253- return [ cyclePaths , cycleNodes ] ;
420+ function visitWithStack ( baseNode , currentNode = baseNode ) {
421+ walkStack . push ( currentNode ) ;
422+ currentNode . localDependents . forEach ( visits . bind ( null , baseNode ) ) ;
423+ walkStack . pop ( ) ;
424+ }
425+
426+ this . forEach ( currentNode => visitWithStack ( currentNode ) ) ;
427+ cycles . forEach ( collapsedNode => visitWithStack ( collapsedNode ) ) ;
428+
429+ reportCycles ( cyclePaths , rejectCycles ) ;
430+
431+ return cycles ;
254432 }
255433
256434 /**
@@ -291,4 +469,18 @@ class PackageGraph extends Map {
291469 }
292470}
293471
472+ function reportCycles ( paths , rejectCycles ) {
473+ if ( ! paths . length ) {
474+ return ;
475+ }
476+
477+ const cycleMessage = [ "Dependency cycles detected, you should fix these!" ] . concat ( paths ) . join ( "\n" ) ;
478+
479+ if ( rejectCycles ) {
480+ throw new ValidationError ( "ECYCLE" , cycleMessage ) ;
481+ }
482+
483+ log . warn ( "ECYCLE" , cycleMessage ) ;
484+ }
485+
294486module . exports = PackageGraph ;
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