From ecb3a8933f2058cfba93e600fccc100473d1df91 Mon Sep 17 00:00:00 2001
From: Evan Wallace <evan.exe@gmail.com>
Date: Sun, 16 Apr 2023 15:46:36 -0400
Subject: [PATCH] fix #3062: watch mode with `NODE_PATH` edge case

---
 CHANGELOG.md            |  4 ++++
 internal/fs/fs_real.go  |  5 ++++-
 scripts/js-api-tests.js | 48 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4bf95ec72b1..bdda24a3c61 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,10 @@
     }
     ```
 
+* Fix watch mode with `NODE_PATH` ([#3062](https://github.com/evanw/esbuild/issues/3062))
+
+    Node has a rarely-used feature where you can extend the set of directories that node searches for packages using the `NODE_PATH` environment variable. While esbuild supports this too, previously a bug prevented esbuild's watch mode from picking up changes to imported files that were contained directly in a `NODE_PATH` directory. You're supposed to use `NODE_PATH` for packages, but some people abuse this feature by putting files in that directory instead (e.g. `node_modules/some-file.js` instead of `node_modules/some-pkg/some-file.js`). The watch mode bug happens when you do this because esbuild first tries to read `some-file.js` as a directory and then as a file. Watch mode was incorrectly waiting for `some-file.js` to become a valid directory. This release fixes this edge case bug by changing watch mode to watch `some-file.js` as a file when this happens.
+
 ## 0.17.16
 
 * Fix CSS nesting transform for triple-nested rules that start with a combinator ([#3046](https://github.com/evanw/esbuild/issues/3046))
diff --git a/internal/fs/fs_real.go b/internal/fs/fs_real.go
index 9adb7059e7a..c8aad07a218 100644
--- a/internal/fs/fs_real.go
+++ b/internal/fs/fs_real.go
@@ -212,7 +212,10 @@ func (fs *realFS) ReadFile(path string) (contents string, canonicalError error,
 		data, ok := fs.watchData[path]
 		if canonicalError != nil {
 			data.state = stateFileMissing
-		} else if !ok {
+		} else if !ok || data.state == stateDirUnreadable {
+			// Note: If "ReadDirectory" is called before "ReadFile" with this same
+			// path, then "data.state" will be "stateDirUnreadable". In that case
+			// we want to transition to "stateFileNeedModKey" because it's a file.
 			data.state = stateFileNeedModKey
 		}
 		data.fileContents = fileContents
diff --git a/scripts/js-api-tests.js b/scripts/js-api-tests.js
index 08a132737d0..b43b4c75302 100644
--- a/scripts/js-api-tests.js
+++ b/scripts/js-api-tests.js
@@ -4062,6 +4062,54 @@ let watchTests = {
       await context.dispose()
     }
   },
+
+  // See: https://github.com/evanw/esbuild/issues/3062
+  async watchNodePaths({ esbuild, testDir }) {
+    const input = path.join(testDir, 'in.js')
+    const outfile = path.join(testDir, 'out.js')
+    const libDir = path.join(testDir, 'lib')
+    const libFile = path.join(libDir, 'foo.js')
+    await mkdirAsync(libDir, { recursive: true })
+    await writeFileAsync(input, `
+      import { foo } from ${JSON.stringify(path.basename(libFile))}
+      console.log(foo)
+    `)
+
+    const { rebuildUntil, plugin } = makeRebuildUntilPlugin()
+    const context = await esbuild.context({
+      entryPoints: [input],
+      outfile,
+      write: false,
+      bundle: true,
+      minifyWhitespace: true,
+      format: 'esm',
+      logLevel: 'silent',
+      plugins: [plugin],
+      nodePaths: [libDir],
+    })
+
+    try {
+      const result = await rebuildUntil(
+        () => {
+          context.watch()
+          writeFileAtomic(libFile, `export let foo = 0`)
+        },
+        result => result.outputFiles.length === 1,
+      )
+      assert.strictEqual(result.outputFiles[0].text, `var foo=0;console.log(foo);\n`)
+
+      // Make sure watch mode works for files imported via NODE_PATH
+      for (let i = 1; i <= 3; i++) {
+        const result2 = await rebuildUntil(
+          () => writeFileAtomic(libFile, `export let foo = ${i}`),
+          result => result.outputFiles.length === 1 && result.outputFiles[0].text.includes(i),
+        )
+        assert.strictEqual(result2.outputFiles[0].text, `var foo=${i};console.log(foo);\n`)
+      }
+    } finally {
+      await context.dispose()
+    }
+  },
 }
 
 let serveTests = {