Allow raw project slugs for fetching lgtm dbs

The following is now acceptable for fetching the codeql lgtm database:

```
g/github/codeql
```

extensions/ql-vscode/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## [UNRELEASED]
 
+- Allow using raw LGTM project slugs for fetching LGTM databases. [#769](https://github.com/github/vscode-codeql/pull/769)
+
 ## 1.4.3 - 22 February 2021
 
 - Avoid displaying an error when removing orphaned databases and the storage folder does not exist. [#748](https://github.com/github/vscode-codeql/pull/748)

extensions/ql-vscode/src/databaseFetcher.ts

@@ -74,7 +74,7 @@ export async function promptImportLgtmDatabase(
 ): Promise<DatabaseItem | undefined> {
   const lgtmUrl = await window.showInputBox({
     prompt:
-      'Enter the project URL on LGTM (e.g., https://lgtm.com/projects/g/github/codeql)',
+      'Enter the project slug or URL on LGTM (e.g., g/github/codeql or https://lgtm.com/projects/g/github/codeql)',
   });
   if (!lgtmUrl) {
     return;
@@ -352,13 +352,14 @@ export async function findDirWithFile(
 
 /**
  * The URL pattern is https://lgtm.com/projects/{provider}/{org}/{name}/{irrelevant-subpages}.
- * There are several possibilities for the provider: in addition to GitHub.com(g),
+ * There are several possibilities for the provider: in addition to GitHub.com (g),
  * LGTM currently hosts projects from Bitbucket (b), GitLab (gl) and plain git (git).
  *
- * After the {provider}/{org}/{name} path components, there may be the components
- * related to sub pages.
+ * This function accepts any url that matches the pattern above. It also accepts the
+ * raw project slug, e.g., `g/myorg/myproject`
  *
- * This function accepts any url that matches the patter above
+ * After the `{provider}/{org}/{name}` path components, there may be the components
+ * related to sub pages.
  *
  * @param lgtmUrl The URL to the lgtm project
  *
@@ -370,6 +371,10 @@ export function looksLikeLgtmUrl(lgtmUrl: string | undefined): lgtmUrl is string
     return false;
   }
 
+  if (convertRawLgtmSlug(lgtmUrl)) {
+    return true;
+  }
+
   try {
     const uri = Uri.parse(lgtmUrl, true);
     if (uri.scheme !== 'https') {
@@ -387,9 +392,23 @@ export function looksLikeLgtmUrl(lgtmUrl: string | undefined): lgtmUrl is string
   }
 }
 
+function convertRawLgtmSlug(maybeSlug: string): string | undefined {
+  if (!maybeSlug) {
+    return;
+  }
+  const segments = maybeSlug.split('/');
+  const providers = ['g', 'gl', 'b', 'git'];
+  if (segments.length === 3 && providers.includes(segments[0])) {
+    return `https://lgtm.com/projects/${maybeSlug}`;
+  }
+  return;
+}
+
 // exported for testing
 export async function convertToDatabaseUrl(lgtmUrl: string) {
   try {
+    lgtmUrl = convertRawLgtmSlug(lgtmUrl) || lgtmUrl;
+
     const uri = Uri.parse(lgtmUrl, true);
     const paths = ['api', 'v1.0'].concat(
       uri.path.split('/').filter((segment) => segment)

extensions/ql-vscode/src/vscode-tests/no-workspace/databaseFetcher.test.ts

@@ -55,6 +55,17 @@ describe('databaseFetcher', function() {
       );
     });
 
+    it('should convert a raw slug to a database url with extra path segments', async () => {
+      quickPickSpy.resolves('python');
+      const lgtmUrl =
+        'g/github/codeql';
+      const dbUrl = await convertToDatabaseUrl(lgtmUrl);
+
+      expect(dbUrl).to.equal(
+        'https://lgtm.com/api/v1.0/snapshots/1506465042581/python'
+      );
+    });
+
     it('should fail on a nonexistant prohect', async () => {
       quickPickSpy.resolves('javascript');
       const lgtmUrl = 'https://lgtm.com/projects/g/github/hucairz';
@@ -71,6 +82,10 @@ describe('databaseFetcher', function() {
         .to.be.false;
       expect(looksLikeLgtmUrl('https://ww.lgtm.com/projects/g/github')).to.be
         .false;
+      expect(looksLikeLgtmUrl('g/github')).to.be
+        .false;
+      expect(looksLikeLgtmUrl('ggg/github/myproj')).to.be
+        .false;
     });
 
     it('should handle valid urls', () => {
@@ -86,6 +101,10 @@ describe('databaseFetcher', function() {
           'https://lgtm.com/projects/g/github/codeql/sub/pages?query=string'
         )
       ).to.be.true;
+      expect(looksLikeLgtmUrl('g/github/myproj')).to.be
+        .true;
+      expect(looksLikeLgtmUrl('git/github/myproj')).to.be
+        .true;
     });
   });