Recursive model errors during flattening stage of generate server

[kstedman9]

Problem statement

I have a recursive model that is separated into a models file that is referred to by "$ref" tag. When I try to generate the server it panics during the flattening process. So you can also test by just running the flattening. If I remove the recursion it works just fine. To remove recursion I just change in the QueryNode model all "$ref": "#/QueryNode" to "type": "object"

Part of the output messages with debug turned on.

analysis:2018/11/16 09:14:15 flatten.go:803: importing external schema for [#/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/and/items, #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/or/items, #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/not/items] from /home/kstedman/projects/develop/swag_issue/models/query.json#/QueryNode
analysis:2018/11/16 09:14:15 flatten.go:807: new name for [#/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/and/items, #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/or/items, #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/not/items]: queryNode - with name conflict:false
analysis:2018/11/16 09:14:15 flatten.go:950: updating ref for #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/and/items with #/definitions/queryNode
analysis:2018/11/16 09:14:15 flatten.go:950: updating ref for #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/or/items with #/definitions/queryNode
analysis:2018/11/16 09:14:15 flatten.go:950: updating ref for #/paths/~1search/post/parameters/0/schema/properties/queryRoot/properties/not/items with #/definitions/queryNode
analysis:2018/11/16 09:14:15 flatten.go:1260: name pointers
analysis:2018/11/16 09:14:15 flatten.go:1272: planning pointer to replace at #/definitions/queryNode/properties/or/items: models/query.json#/QueryNode, resolved to: models/query.json#/QueryNode
analysis:2018/11/16 09:14:15 flatten.go:1272: planning pointer to replace at #/definitions/queryNode/properties/and/items: models/query.json#/QueryNode, resolved to: models/query.json#/QueryNode
analysis:2018/11/16 09:14:15 flatten.go:1272: planning pointer to replace at #/definitions/queryNode/properties/not/items: models/query.json#/QueryNode, resolved to: models/query.json#/QueryNode
analysis:2018/11/16 09:14:15 flatten.go:1298: replacing pointer at #/definitions/queryNode/properties/and/items: resolved to: models/query.json#/QueryNode
analysis:2018/11/16 09:14:15 flatten.go:1314: namePointers at #/definitions/queryNode/properties/and/items for models/query.json#/QueryNode
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x1a0 pc=0x7dab09]

goroutine 1 [running]:
github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis.(*AnalyzedSchema).initializeFlags(0xc0005e21c0)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis/schema.go:213 +0x29
github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis.Schema(0x0, 0xb32600, 0xc0002cc700, 0xc000690c40, 0x3a, 0x0, 0xc00046a580, 0xc0007868e0, 0x1)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis/schema.go:25 +0x97
github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis.namePointers(0xc0006e8330, 0xc0007799a0, 0x7bae49)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis/flatten.go:1317 +0xed1
github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis.stripPointersAndOAIGen(0xc0006e8330, 0x0, 0x0)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis/flatten.go:1130 +0x2f
github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis.Flatten(0xc000695180, 0x0, 0x7ffe431501cb, 0xf, 0x10101, 0x8, 0x7)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/go-openapi/analysis/flatten.go:182 +0x2e5
github.com/go-swagger/go-swagger/cmd/swagger/commands.(*FlattenSpec).Execute(0xc00008e690, 0xc00039f080, 0x1, 0x6, 0xc00008e690, 0x1)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/cmd/swagger/commands/flatten.go:43 +0x18f
github.com/go-swagger/go-swagger/vendor/github.com/jessevdk/go-flags.(*Parser).ParseArgs(0xc00039f020, 0xc00001e080, 0x6, 0x6, 0x40dac8, 0x30, 0xb7ba60, 0xc000092990, 0xc000431b00)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/jessevdk/go-flags/parser.go:316 +0x800
github.com/go-swagger/go-swagger/vendor/github.com/jessevdk/go-flags.(*Parser).Parse(0xc00039f020, 0x6, 0xbcba2a, 0x6, 0x0, 0xc16ff0)
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/vendor/github.com/jessevdk/go-flags/parser.go:186 +0x71
main.main()
	/home/kstedman/go/src/github.com/go-swagger/go-swagger/cmd/swagger/swagger.go:140 +0xb68

Swagger specification

So I have a swagger json definition. The top level file contains the paths. Models are found in a subfolder models. FYI this is a small part of a very large swagger project.

./queryIssue.json

{
  "swagger": "2.0",
  "info": {
    "title": "Query Model Issue",
    "description": "Test for Query Model Issue",
    "version": "0.0.1"
  },
  "schemes": ["http"],
  "produces": ["application/json"],
  "paths": {
 
    "/search": {
      "post": {
        "operationId": "searchObject",
        "tags": ["Query"],
        "produces": ["application/json"],
        "consumes": ["application/json"],
        "security": [
          {
            "Bearer": []
          }
        ],
        "summary":
          "Get a list of the algorithms available in the AlgorithmBank instance. By default returns the first 10 results.",
        "parameters": [
          {
            "name": "query",
            "in": "body",
            "required": true,
            "schema": {
              "$ref": "./models/query.json#/Query"
            }
          }
        ], 
        "responses": {
          "200": {
            "description": "OK",
            "schema": {
              "type": "string"
            }
          },
          "400": {
            "description": "Invalid parameters."
          },
          "401": {
            "description": "Unauthenticated."
          },
          "403": {
            "description": "User is not authorized to perform the action",
            "schema": {
              "type": "string"
            }
          },
          "500": {
            "description": "Internal Server Error",
            "schema": {
              "type": "string"
            }
          }
        }
      }
    }
  },
  "definitions": {

  }
}

./models/query.json:

{
    "Query": {
       "description":
         "Represents a search query using a boolean expression tree",
       "type": "object",
       "properties": {
         "queryRoot": {
           "$ref": "#/QueryNode"
         },
         "limit": {
           "type": "integer",
           "format": "int64"
         },
         "offset": {
           "type": "integer",
           "format": "int64"
         }
       },
       "x-go-type": {
           "import": {
              "package": "bitbucket.di2e.net/scm/pir/ab-models.git",
              "alias": "models"
           },
           "type": "Query"
       }
     },
     "QueryNode": {
      "description":
        "Node in a boolean expression tree that represents a query",
      "type": "object",
      "properties": {
        "and": {
          "type": "array",
          "items": {
            "$ref": "#/QueryNode"
          }
        },
        "or": {
          "type": "array",
          "items": {
            "$ref": "#/QueryNode"
          }
        },
        "not": {
          "type": "array",
          "items": {
            "$ref": "#/QueryNode"
          }
        },
        "wildcards": {
          "description":
            "Array of key/value pairs representing wildcard term matches",
          "type": "array",
          "items": {
            "$ref": "./pair.json#/Pair"
          }
        },
        "exact": {
          "description":
            "Array of key/value pairs representing exact term matches",
          "type": "array",
          "items": {
            "$ref": "./pair.json#/Pair"
          }
        }
      },
      "x-go-type": {
          "import": {
            "package": "bitbucket.di2e.net/scm/pir/ab-models.git",
            "alias": "models"
          },
          "type": "QueryNode"
      }
    }
 }

./models/pair.json:

{
    "Pair": {
        "description":
          "Simple key value pair model that is used by some of the other models.",
        "type": "object",
        "required": ["key", "value"],
        "properties": {
          "key": {
            "type": "string"
          },
          "value": {
            "type": "string"
          }
        },
        "x-go-type": {
            "import": {
              "package": "bitbucket.di2e.net/scm/pir/ab-models.git",
              "alias": "abmodels"
            },
            "type": "Pair"
        }
     }
  }

Steps to reproduce

Run: swagger flatten -o queryIssueFlatten.json --format=json --with-expand queryIssue.json
or
Run: swagger generate server -f queryIssue.json -A queryissue

Both commands give the same issue

Environment

swagger version: 0.17.2 and master branch
go version: 1.10.x, 1.11.x
OS: Centos 7

Attached are all the json files and the complete log output.
issue.zip

[fredbi]

Could reproduce in go-openapi/analyis. There are still some cyclic ref patterns that cause some bugs...

[fredbi]

I think I solved the issue in go-openapi analysis.
Some feedback would be much valuable: go-openapi/analysis#40