fix: implement longest prefix matching for pathMappings (closes #331) (#363)

* fix: implement longest prefix matching for pathMappings (closes #331)

* test: add test cases for server path longest prefix matching

Based on the test cases over at
robberphex/vscode-php-debug@729be1d. Thanks @robberphex!

Author: bjoluc

src/paths.ts

@@ -46,9 +46,13 @@ export function convertDebuggerPathToClient(
             // normalize slashes for windows-to-unix
             const serverRelative = (serverIsWindows ? path.win32 : path.posix).relative(mappedServerPath, serverPath)
             if (serverRelative.indexOf('..') !== 0) {
-                serverSourceRoot = mappedServerPath
-                localSourceRoot = mappedLocalSource
-                break
+                // If a matching mapping has previously been found, only update
+                // it if the current server path is longer than the previous one
+                // (longest prefix matching)
+                if (!serverSourceRoot || mappedServerPath.length > serverSourceRoot.length) {
+                    serverSourceRoot = mappedServerPath
+                    localSourceRoot = mappedLocalSource
+                }
             }
         }
     }
@@ -82,9 +86,13 @@ export function convertClientPathToDebugger(localPath: string, pathMapping?: { [
             const mappedLocalSource = pathMapping[mappedServerPath]
             const localRelative = path.relative(mappedLocalSource, localPath)
             if (localRelative.indexOf('..') !== 0) {
-                serverSourceRoot = mappedServerPath
-                localSourceRoot = mappedLocalSource
-                break
+                // If a matching mapping has previously been found, only update
+                // it if the current local path is longer than the previous one
+                // (longest prefix matching)
+                if (!localSourceRoot || mappedLocalSource.length > localSourceRoot.length) {
+                    serverSourceRoot = mappedServerPath
+                    localSourceRoot = mappedLocalSource
+                }
             }
         }
     }

src/test/paths.ts

@@ -55,6 +55,15 @@ describe('paths', () => {
                     }),
                     'file:///app/source.php'
                 )
+                // longest prefix matching for server paths
+                assert.strictEqual(
+                    convertClientPathToDebugger('/home/felix/mysource/subdir/source.php', {
+                        '/var/www': '/home/felix/mysite',
+                        '/app/subdir1': '/home/felix/mysource/subdir',
+                        '/app': '/home/felix/mysource',
+                    }),
+                    'file:///app/subdir1/source.php'
+                )
             })
             // unix to windows
             it('should convert a unix path to a windows URI', () => {
@@ -165,6 +174,15 @@ describe('paths', () => {
                     }),
                     '/home/felix/mysource/source.php'
                 )
+                // longest prefix matching for local paths
+                assert.strictEqual(
+                    convertDebuggerPathToClient('file:///app/subdir/source.php', {
+                        '/var/www': '/home/felix/mysite',
+                        '/app/subdir': '/home/felix/mysource/subdir1',
+                        '/app': '/home/felix/mysource',
+                    }),
+                    '/home/felix/mysource/subdir1/source.php'
+                )
             })
             // unix to windows
             ;(process.platform === 'win32' ? it : it.skip)('should map unix uris to windows paths', () => {