3 files changed, 333 insertions, 69 deletions

diff --git a/lib/utils/explain-eresolve.js b/lib/utils/explain-eresolve.js
index 69789ec9a..cda77aff9 100644
--- a/lib/utils/explain-eresolve.js
+++ b/lib/utils/explain-eresolve.js
@@ -15,13 +15,20 @@ const { explainEdge, explainNode, printNode } = require('./explain-dep.js')
 // The full report (ie, depth=Infinity) is always written to the cache folder
 // at ${cache}/eresolve-report.txt along with full json.
 const explainEresolve = (expl, color, depth) => {
-  const { edge, current, peerConflict } = expl
+  const { edge, current, peerConflict, currentEdge } = expl
 
   const out = []
   if (edge.from && edge.from.whileInstalling)
     out.push('While resolving: ' + printNode(edge.from.whileInstalling, color))
 
-  out.push('Found: ' + explainNode(current, depth, color))
+  // it "should" be impossible for an ERESOLVE explanation to lack both
+  // current and currentEdge, but better to have a less helpful error
+  // than a crashing failure.
+  if (current)
+    out.push('Found: ' + explainNode(current, depth, color))
+  else if (currentEdge)
+    out.push('Found: ' + explainEdge(currentEdge, depth, color))
+
   out.push('\nCould not resolve dependency:\n' +
     explainEdge(edge, depth, color))
 
diff --git a/tap-snapshots/test-lib-utils-explain-eresolve.js-TAP.test.js b/tap-snapshots/test-lib-utils-explain-eresolve.js-TAP.test.js
index 87dcb861c..e06668015 100644
--- a/tap-snapshots/test-lib-utils-explain-eresolve.js-TAP.test.js
+++ b/tap-snapshots/test-lib-utils-explain-eresolve.js-TAP.test.js
@@ -418,6 +418,188 @@ to accept an incorrect (and potentially broken) dependency resolution.
 See \${REPORT} for a full report.
 `
 
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > explain with color 1`] = `
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > explain with no color, depth of 6 1`] = `
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > report 1`] = `
+# npm resolution error report
+
+\${TIME}
+
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+Raw JSON explanation object:
+
+{
+  "name": "no current node, but has current edge",
+  "json": true
+}
+
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > report with color 1`] = `
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > report with color, depth only 2 1`] = `
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, but has current edge > report with no color, depth of 6 1`] = `
+While resolving: eslint@7.22.0
+Found: dev eslint@"file:." from the root project
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > explain with color 1`] = `
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > explain with no color, depth of 6 1`] = `
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > report 1`] = `
+# npm resolution error report
+
+\${TIME}
+
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+Raw JSON explanation object:
+
+{
+  "name": "no current node, no current edge, idk",
+  "json": true
+}
+
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > report with color 1`] = `
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > report with color, depth only 2 1`] = `
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
+exports[`test/lib/utils/explain-eresolve.js TAP no current node, no current edge, idk > report with no color, depth of 6 1`] = `
+While resolving: eslint@7.22.0
+
+Could not resolve dependency:
+peer eslint@"^6.0.0" from eslint-plugin-jsdoc@22.2.0
+node_modules/eslint-plugin-jsdoc
+  dev eslint-plugin-jsdoc@"^22.1.0" from the root project
+
+Fix the upstream dependency conflict, or retry
+this command with --force, or --legacy-peer-deps
+to accept an incorrect (and potentially broken) dependency resolution.
+
+See \${REPORT} for a full report.
+`
+
 exports[`test/lib/utils/explain-eresolve.js TAP withShrinkwrap > explain with color 1`] = `
 While resolving: @isaacs/peer-dep-cycle-b@1.0.0
 Found: @isaacs/peer-dep-cycle-c@2.0.0
diff --git a/test/fixtures/eresolve-explanations.js b/test/fixtures/eresolve-explanations.js
index c5c338e61..b6ccac7d3 100644
--- a/test/fixtures/eresolve-explanations.js
+++ b/test/fixtures/eresolve-explanations.js
@@ -16,10 +16,10 @@ module.exports = {
             type: 'prod',
             name: '@isaacs/peer-dep-cycle-a',
             spec: '1.x',
-            from: { location: '/some/project' }
-          }
-        ]
-      }
+            from: { location: '/some/project' },
+          },
+        ],
+      },
     },
     current: {
       name: '@isaacs/peer-dep-cycle-c',
@@ -30,9 +30,9 @@ module.exports = {
           type: 'prod',
           name: '@isaacs/peer-dep-cycle-c',
           spec: '2.x',
-          from: { location: '/some/project' }
-        }
-      ]
+          from: { location: '/some/project' },
+        },
+      ],
     },
     peerConflict: {
       name: '@isaacs/peer-dep-cycle-c',
@@ -63,15 +63,15 @@ module.exports = {
                       type: 'prod',
                       name: '@isaacs/peer-dep-cycle-a',
                       spec: '1.x',
-                      from: { location: '/some/project' }
-                    }
-                  ]
-                }
-              }
-            ]
-          }
-        }
-      ]
+                      from: { location: '/some/project' },
+                    },
+                  ],
+                },
+              },
+            ],
+          },
+        },
+      ],
     },
     strictPeerDeps: true,
   },
@@ -102,13 +102,13 @@ module.exports = {
                   type: 'prod',
                   name: '@isaacs/peer-dep-cycle-a',
                   spec: '1.x',
-                  from: { location: '/some/project' }
-                }
-              ]
-            }
-          }
-        ]
-      }
+                  from: { location: '/some/project' },
+                },
+              ],
+            },
+          },
+        ],
+      },
     },
     current: {
       name: '@isaacs/peer-dep-cycle-c',
@@ -119,9 +119,9 @@ module.exports = {
           type: 'prod',
           name: '@isaacs/peer-dep-cycle-c',
           spec: '2.x',
-          from: { location: '/some/project' }
-        }
-      ]
+          from: { location: '/some/project' },
+        },
+      ],
     },
     strictPeerDeps: true,
   },
@@ -134,7 +134,7 @@ module.exports = {
       whileInstalling: {
         name: 'project',
         version: '1.2.3',
-        path: '/some/project'
+        path: '/some/project',
       },
       location: 'node_modules/@isaacs/testing-peer-dep-conflict-chain-d',
       dependents: [
@@ -142,9 +142,9 @@ module.exports = {
           type: 'prod',
           name: '@isaacs/testing-peer-dep-conflict-chain-d',
           spec: '2',
-          from: { location: '/some/project' }
-        }
-      ]
+          from: { location: '/some/project' },
+        },
+      ],
     },
     edge: {
       type: 'peer',
@@ -157,7 +157,7 @@ module.exports = {
         whileInstalling: {
           name: 'project',
           version: '1.2.3',
-          path: '/some/project'
+          path: '/some/project',
         },
         location: 'node_modules/@isaacs/testing-peer-dep-conflict-chain-c',
         dependents: [
@@ -165,13 +165,13 @@ module.exports = {
             type: 'prod',
             name: '@isaacs/testing-peer-dep-conflict-chain-c',
             spec: '1',
-            from: { location: '/some/project' }
-          }
-        ]
-      }
+            from: { location: '/some/project' },
+          },
+        ],
+      },
     },
     peerConflict: null,
-    strictPeerDeps: false
+    strictPeerDeps: false,
   },
 
   gatsby: {
@@ -182,7 +182,7 @@ module.exports = {
       whileInstalling: {
         name: 'gatsby-recipes',
         version: '0.2.31',
-        path: '/some/project/node_modules/gatsby-recipes'
+        path: '/some/project/node_modules/gatsby-recipes',
       },
       location: 'node_modules/ink',
       dependents: [
@@ -218,19 +218,19 @@ module.exports = {
                             name: 'gatsby',
                             spec: '',
                             from: {
-                              location: '/some/project/gatsby-user'
-                            }
-                          }
-                        ]
-                      }
-                    }
-                  ]
-                }
-              }
-            ]
-          }
-        }
-      ]
+                              location: '/some/project/gatsby-user',
+                            },
+                          },
+                        ],
+                      },
+                    },
+                  ],
+                },
+              },
+            ],
+          },
+        },
+      ],
     },
     edge: {
       type: 'peer',
@@ -243,7 +243,7 @@ module.exports = {
         whileInstalling: {
           name: 'gatsby-recipes',
           version: '0.2.31',
-          path: '/some/project/gatsby-user/node_modules/gatsby-recipes'
+          path: '/some/project/gatsby-user/node_modules/gatsby-recipes',
         },
         location: 'node_modules/ink-box',
         dependents: [
@@ -279,23 +279,98 @@ module.exports = {
                               name: 'gatsby',
                               spec: '',
                               from: {
-                                location: '/some/project/gatsby-user'
-                              }
-                            }
-                          ]
-                        }
-                      }
-                    ]
-                  }
-                }
-              ]
-            }
-          }
-        ]
-      }
+                                location: '/some/project/gatsby-user',
+                              },
+                            },
+                          ],
+                        },
+                      },
+                    ],
+                  },
+                },
+              ],
+            },
+          },
+        ],
+      },
     },
     peerConflict: null,
-    strictPeerDeps: true
-  }
+    strictPeerDeps: true,
+  },
 
+  'no current node, but has current edge': {
+    code: 'ERESOLVE',
+    current: null,
+    currentEdge: {
+      type: 'dev',
+      name: 'eslint',
+      spec: 'file:.',
+      error: 'MISSING',
+      from: {
+        location: '/some/projects/eslint',
+      },
+    },
+    edge: {
+      type: 'peer',
+      name: 'eslint',
+      spec: '^6.0.0',
+      error: 'MISSING',
+      from: {
+        name: 'eslint-plugin-jsdoc',
+        version: '22.2.0',
+        whileInstalling: {
+          name: 'eslint',
+          version: '7.22.0',
+          path: '/Users/isaacs/dev/npm/cli/eslint',
+        },
+        location: 'node_modules/eslint-plugin-jsdoc',
+        dependents: [
+          {
+            type: 'dev',
+            name: 'eslint-plugin-jsdoc',
+            spec: '^22.1.0',
+            from: {
+              location: '/some/projects/eslint',
+            },
+          },
+        ],
+      },
+    },
+    peerConflict: null,
+    strictPeerDeps: false,
+    force: false,
+  },
+  'no current node, no current edge, idk': {
+    code: 'ERESOLVE',
+    current: null,
+    edge: {
+      type: 'peer',
+      name: 'eslint',
+      spec: '^6.0.0',
+      error: 'MISSING',
+      from: {
+        name: 'eslint-plugin-jsdoc',
+        version: '22.2.0',
+        whileInstalling: {
+          name: 'eslint',
+          version: '7.22.0',
+          path: '/Users/isaacs/dev/npm/cli/eslint',
+        },
+        location: 'node_modules/eslint-plugin-jsdoc',
+        dependents: [
+          {
+            type: 'dev',
+            name: 'eslint-plugin-jsdoc',
+            spec: '^22.1.0',
+            from: {
+              location: '/some/projects/eslint',
+            },
+          },
+        ],
+      },
+    },
+    peerConflict: null,
+    strictPeerDeps: false,
+    force: false,
+  },
 }