Python: Fix 'unused import' to no longer give alerts for imported modules used in doctests.

markshannon · markshannon · commit 9f93bf8d17c9 · 2019-01-18T11:08:53.000Z
diff --git a/change-notes/1.20/analysis-python.md b/change-notes/1.20/analysis-python.md
@@ -16,6 +16,7 @@
 
  | **Query**                  | **Expected impact**    | **Change**                                                       |
 |----------------------------|------------------------|------------------------------------------------------------------|
+| Unused import (`py/unused-import`) | Fewer false positive results | Results where the imported module is used in a doctest string are no longer reported |
 
  ## Changes to code extraction
 
diff --git a/python/ql/src/Imports/UnusedImport.ql b/python/ql/src/Imports/UnusedImport.ql
@@ -41,6 +41,22 @@ predicate all_not_understood(Module m) {
     )
 }
 
+predicate imported_module_used_in_doctest(Import imp) {
+    exists(string modname |
+        ((Name)imp.getAName().getAsname()).getId() = modname
+        and
+        /* Look for doctests containing the patterns:
+         * >>> …name…
+         * ... …name…
+         */
+        exists(StrConst doc |
+            doc.getEnclosingModule() = imp.getScope() and
+            doc.isDocString() and
+            doc.getText().regexpMatch("[\\s\\S]*(>>>|\\.\\.\\.).*" + modname + "[\\s\\S]*")
+        )
+    )
+}
+
 predicate unused_import(Import imp, Variable name) {
     ((Name)imp.getAName().getAsname()).getVariable() = name
     and
@@ -65,6 +81,8 @@ predicate unused_import(Import imp, Variable name) {
     and
     /* Assume that opaque `__all__` includes imported module */
     not all_not_understood(imp.getEnclosingModule())
+    and
+    not imported_module_used_in_doctest(imp)
 }
 
 
diff --git a/python/ql/src/semmle/python/strings.qll b/python/ql/src/semmle/python/strings.qll
@@ -57,3 +57,4 @@ string repr(Expr e) {
    else
        result = e.toString()
 }
+
diff --git a/python/ql/test/query-tests/Imports/unused/imports_test.py b/python/ql/test/query-tests/Imports/unused/imports_test.py
@@ -61,3 +61,12 @@ def __init__(self):
 #Use it
 different
 
+import used_in_doctest
+
+def f():
+    '''
+    >>> unrelated
+    >>> used_in_doctest.thing() == f()
+    True
+    '''
+    return 5

Original file line number	Diff line number	Diff line change
`@@ -57,3 +57,4 @@ string repr(Expr e) {`
`57`	`57`	`else`
`58`	`58`	`result = e.toString()`
`59`	`59`	`}`
	`60`	`+`