From de781fdc26c4ca8f652775e7751515c0ea2a68d1 Mon Sep 17 00:00:00 2001
From: Hood Chatham <hood@mit.edu>
Date: Tue, 7 Sep 2021 09:42:51 -0700
Subject: [PATCH] Handle syntax error in find_imports (#1819)

---
 docs/project/changelog.md |  4 ++++
 src/py/_pyodide/_base.py  |  8 ++++++--
 src/tests/test_pyodide.py | 24 +++++++++++++++++-------
 3 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/docs/project/changelog.md b/docs/project/changelog.md
index 7215eedad..ee00ad45c 100644
--- a/docs/project/changelog.md
+++ b/docs/project/changelog.md
@@ -57,6 +57,10 @@ substitutions:
 - {{Fix}} Fixed a use after free bug in the error handling code.
   {pr}`1816`
 
+- {{Enhancement}} If `find_imports` is used on code that contains a syntax
+  error, it will return an empty list instead of raising a `SyntaxError`.
+  {pr}`1819`
+
 ## Version 0.18.0
 
 _August 3rd, 2021_
diff --git a/src/py/_pyodide/_base.py b/src/py/_pyodide/_base.py
index 7fb361a7f..b857d5c9c 100644
--- a/src/py/_pyodide/_base.py
+++ b/src/py/_pyodide/_base.py
@@ -515,7 +515,8 @@ def find_imports(source: str) -> List[str]:
     Returns
     -------
     ``List[str]``
-        A list of module names that are imported in ``source``.
+        A list of module names that are imported in ``source``. If ``source`` is not
+        syntactically correct Python code (after dedenting), returns an empty list.
 
     Examples
     --------
@@ -527,7 +528,10 @@ def find_imports(source: str) -> List[str]:
     # handle mis-indented input from multi-line strings
     source = dedent(source)
 
-    mod = ast.parse(source)
+    try:
+        mod = ast.parse(source)
+    except SyntaxError:
+        return []
     imports = set()
     for node in ast.walk(mod):
         if isinstance(node, ast.Import):
diff --git a/src/tests/test_pyodide.py b/src/tests/test_pyodide.py
index ca1af4c2b..db8098cd2 100644
--- a/src/tests/test_pyodide.py
+++ b/src/tests/test_pyodide.py
@@ -11,16 +11,26 @@ from pyodide import find_imports, eval_code, CodeRunner, should_quiet  # noqa: E
 def test_find_imports():
 
     res = find_imports(
-        dedent(
-            """
-           import numpy as np
-           from scipy import sparse
-           import matplotlib.pyplot as plt
-           """
-        )
+        """
+        import numpy as np
+        from scipy import sparse
+        import matplotlib.pyplot as plt
+        """
     )
     assert set(res) == {"numpy", "scipy", "matplotlib"}
 
+    # If there is a syntax error in the code, find_imports should return empty
+    # list.
+    res = find_imports(
+        """
+        import numpy as np
+        from scipy import sparse
+        import matplotlib.pyplot as plt
+        for x in [1,2,3]
+        """
+    )
+    assert res == []
+
 
 def test_code_runner():
     assert should_quiet("1+1;")