Do not suggest paths inside node_modules/.pnpm as module specifiers (#42095)

* Create symlink cache when a pnpm module is found

* Keep pnpm-internal symlinks out of the symlink cache

* Filter out  pnpm path from realpath module specifier too

* Use ignoredPaths instead of pnpm-specific path

src/compiler/moduleSpecifiers.ts

@@ -290,7 +290,9 @@ namespace ts.moduleSpecifiers {
         const importedFileNames = [...(referenceRedirect ? [referenceRedirect] : emptyArray), importedFileName, ...redirects];
         const targets = importedFileNames.map(f => getNormalizedAbsolutePath(f, cwd));
         if (!preferSymlinks) {
-            const result = forEach(targets, p => cb(p, referenceRedirect === p));
+            // Symlinks inside ignored paths are already filtered out of the symlink cache,
+            // so we only need to remove them from the realpath filenames.
+            const result = forEach(targets, p => !containsIgnoredPath(p) && cb(p, referenceRedirect === p));
             if (result) return result;
         }
         const links = host.getSymlinkCache
@@ -318,8 +320,9 @@ namespace ts.moduleSpecifiers {
                 }
             });
         });
-        return result ||
-            (preferSymlinks ? forEach(targets, p => cb(p, p === referenceRedirect)) : undefined);
+        return result || (preferSymlinks
+            ? forEach(targets, p => containsIgnoredPath(p) ? undefined : cb(p, p === referenceRedirect))
+            : undefined);
     }
 
     interface ModulePath {

src/compiler/program.ts

@@ -3756,7 +3756,7 @@ namespace ts {
         }
 
         function handleDirectoryCouldBeSymlink(directory: string) {
-            if (!host.getResolvedProjectReferences()) return;
+            if (!host.getResolvedProjectReferences() || containsIgnoredPath(directory)) return;
 
             // Because we already watch node_modules, handle symlinks in there
             if (!originalRealpath || !stringContains(directory, nodeModulesPathPart)) return;

src/compiler/utilities.ts

@@ -6092,7 +6092,14 @@ namespace ts {
             getSymlinkedFiles: () => symlinkedFiles,
             getSymlinkedDirectories: () => symlinkedDirectories,
             setSymlinkedFile: (path, real) => (symlinkedFiles || (symlinkedFiles = new Map())).set(path, real),
-            setSymlinkedDirectory: (path, directory) => (symlinkedDirectories || (symlinkedDirectories = new Map())).set(path, directory),
+            setSymlinkedDirectory: (path, directory) => {
+                // Large, interconnected dependency graphs in pnpm will have a huge number of symlinks
+                // where both the realpath and the symlink path are inside node_modules/.pnpm. Since
+                // this path is never a candidate for a module specifier, we can ignore it entirely.
+                if (!containsIgnoredPath(path)) {
+                    (symlinkedDirectories || (symlinkedDirectories = new Map())).set(path, directory);
+                }
+            }
         };
     }
 
@@ -7066,4 +7073,8 @@ namespace ts {
             return false;
         }
     }
+
+    export function containsIgnoredPath(path: string) {
+        return some(ignoredPaths, p => stringContains(path, p));
+    }
 }

src/harness/fourslashImpl.ts

@@ -3022,7 +3022,7 @@ namespace FourSlash {
                  this.editScriptAndUpdateMarkers(fileName, span.start, span.start + insertedText.length, deletedText);
             }
             if (expectedTextArray.length !== actualTextArray.length) {
-                this.raiseError(`Expected ${expectedTextArray.length} import fixes, got ${actualTextArray.length}`);
+                this.raiseError(`Expected ${expectedTextArray.length} import fixes, got ${actualTextArray.length}:\n\n${actualTextArray.join("\n\n" + "-".repeat(20) + "\n\n")}`);
             }
             ts.zipWith(expectedTextArray, actualTextArray, (expected, actual, index) => {
                 if (expected !== actual) {