API docs: do not panic on missing type information from obscure main-…

…exported types (#185)

* API docs: do not panic on missing type information from obscure main-exported types

Prior to this change, we would panic (nil pointer deref) in the event that we
encounter an exported type inside of a `package main` (which is non-sensical and
a linter error in Go):

```
package main

type Foo struct{}

func main() {}
```

This may be a bug in `go/packages`, since we are able to pick up type information for
the `main` symbol itself (ironic!) - but I'm not sure. For now, at least don't panic
/ fail to index everything else.

Signed-off-by: Stephen Gutekanst <[email protected]>

CHANGELOG.md

@@ -11,22 +11,26 @@ All notable changes to `lsif-go` are documented in this file.
 
 ## Unreleased changes
 
+### Fixed
+
+- An issue where indexing would fail if `package main` contained exported data types. [#185](https://github.com/sourcegraph/lsif-go/pull/185)
+
 ## v1.6.3
 
-## Changed
+### Changed
 
 - Improved error messages.
 
 ## v1.6.2
 
-## Fixed
+### Fixed
 
 - API docs no longer incorrectly tags Functions/Variables/etc sections as a package.
 - API docs no longer emits null tag lists in violation of the spec.
 
 ## v1.6.1
 
-## Fixed
+### Fixed
 
 - API docs no longer incorrectly tags some methods as functions and vice-versa.
 

internal/indexer/documentation.go

@@ -544,9 +544,11 @@ func (d *docsIndexer) indexGenDecl(p *packages.Package, f *ast.File, node *ast.G
 				// Not only is it not exported, it cannot be referenced outside this package at all.
 				continue
 			}
-			typeDocs := d.indexTypeSpec(p, t, isTestFile)
-			typeDocs.docsMarkdown = blockDocsMarkdown + typeDocs.docsMarkdown
-			result.types = append(result.types, typeDocs)
+			typeDocs, ok := d.indexTypeSpec(p, t, isTestFile)
+			if ok {
+				typeDocs.docsMarkdown = blockDocsMarkdown + typeDocs.docsMarkdown
+				result.types = append(result.types, typeDocs)
+			}
 		}
 	}
 	return result
@@ -689,7 +691,17 @@ func (t typeDocs) result() *documentationResult {
 	}
 }
 
-func (d *docsIndexer) indexTypeSpec(p *packages.Package, in *ast.TypeSpec, isTestFile bool) typeDocs {
+func (d *docsIndexer) indexTypeSpec(p *packages.Package, in *ast.TypeSpec, isTestFile bool) (typeDocs, bool) {
+	if p.TypesInfo.TypeOf(in.Type) == nil || p.TypesInfo.ObjectOf(in.Name) == nil {
+		// TODO(slimsag): It's unclear why, but exported types declared in a `package main` - such
+		// as `type User struct` in minimal_main.go - do not have type information and would result
+		// in a nil pointer deref below.
+		//
+		// Will need to investigate/fix this at a later point - it may be a bug in go/packages.
+		// But, for now, at least don't panic - just discard it. This is a pretty rare occurrence
+		// anyway, as an exported type from package main is also a linter error / non-idiomatic.
+		return typeDocs{}, false
+	}
 	var result typeDocs
 	result.label = fmt.Sprintf("type %s %s", in.Name.String(), formatTypeLabel(p.TypesInfo.TypeOf(in.Type)))
 	result.name = in.Name.String()
@@ -713,7 +725,7 @@ func (d *docsIndexer) indexTypeSpec(p *packages.Package, in *ast.TypeSpec, isTes
 	result.signature = "type " + formatNode(p.Fset, &cpy)
 
 	result.docsMarkdown = godocToMarkdown(in.Doc.Text())
-	return result
+	return result, true
 }
 
 type funcDocs struct {

internal/indexer/testdata/TestIndexer_documentation/testdata/index.json

@@ -1082,6 +1082,29 @@
               "children": null
             }
           },
+          {
+            "node": {
+              "pathID": "/#main",
+              "documentation": {
+                "identifier": "main",
+                "newPage": false,
+                "searchKey": "testdata.main",
+                "tags": [
+                  "function",
+                  "private"
+                ]
+              },
+              "label": {
+                "kind": "plaintext",
+                "value": "func main()"
+              },
+              "detail": {
+                "kind": "markdown",
+                "value": "```Go\nfunc main()\n```\n\n"
+              },
+              "children": null
+            }
+          },
           {
             "node": {
               "pathID": "/#useOfCompositeStructs",

internal/indexer/testdata/TestIndexer_documentation/testdata/index.md

@@ -56,6 +56,7 @@ testdata is a small package containing sample Go source code used for testing th
 * [Functions](#func)
     * [func Parallel(ctx context.Context, fns ...ParallelizableFunc) error](#Parallel)
     * [func Switch(interfaceValue interface{}) bool](#Switch)
+    * [func main()](#main)
     * [func useOfCompositeStructs()](#useOfCompositeStructs)
 
 
@@ -687,6 +688,17 @@ tags: [function]
 func Switch(interfaceValue interface{}) bool
 ```
 
+### <a id="main" href="#main">func main()</a>
+
+```
+searchKey: testdata.main
+tags: [function private]
+```
+
+```Go
+func main()
+```
+
 ### <a id="useOfCompositeStructs" href="#useOfCompositeStructs">func useOfCompositeStructs()</a>
 
 ```

internal/testdata/minimal_main.go

@@ -0,0 +1,9 @@
+package main
+
+type User struct {
+	Id, Name string
+}
+
+type UserResource struct{}
+
+func main() {}