feat(checkSyntax): create checkSyntaxStdin

index.ts

@@ -322,6 +322,48 @@ export class PythonShell extends EventEmitter {
     });
   }
 
+  /**
+   * checks syntax via stdin without writing to a temp file
+   * @param code The Python code to check
+   * @returns rejects promise w/ stderr if syntax failure
+   */
+  static checkSyntaxStdin(
+    code: string,
+  ): Promise<{ stdout: string; stderr: string }> {
+    return new Promise((resolve, reject) => {
+      const pythonPath = this.getPythonPath();
+      const child = spawn(pythonPath, [
+        '-c',
+        'import sys; compile(sys.stdin.read(), "<stdin>", "exec")',
+      ]);
+
+      const outputBuffers = { stdout: '', stderr: '' };
+
+      child.stdout.on('data', (data) => {
+        outputBuffers.stdout += data.toString();
+      });
+
+      child.stderr.on('data', (data) => {
+        outputBuffers.stderr += data.toString();
+      });
+
+      child.on('close', (exitCode) => {
+        if (exitCode === 0) {
+          resolve(outputBuffers);
+          return;
+        }
+        reject(outputBuffers.stderr || `Process exited with code ${exitCode}`);
+      });
+
+      child.on('error', (err) => {
+        reject(err);
+      });
+
+      child.stdin.write(code);
+      child.stdin.end();
+    });
+  }
+
   static getPythonPath() {
     return this.defaultOptions.pythonPath
       ? this.defaultOptions.pythonPath

test/test-python-shell.ts

@@ -1,8 +1,9 @@
 import * as should from 'should';
 import { PythonShell } from '..';
 import { sep, join } from 'path';
-import { EOL as newline } from 'os';
+import { EOL as newline, tmpdir } from 'os';
 import { chdir, cwd } from 'process';
+import { readdirSync } from 'fs';
 
 describe('PythonShell', function () {
   const pythonFolder = 'test/python';
@@ -98,6 +99,66 @@ describe('PythonShell', function () {
     });
   });
 
+  describe('#checkSyntaxStdin(code:string)', function () {
+    it('should not create temp files', function (done) {
+      const tmpFiles = readdirSync(tmpdir()).filter((f) =>
+        f.startsWith('pythonShellSyntaxCheck'),
+      );
+      const beforeCount = tmpFiles.length;
+
+      PythonShell.checkSyntaxStdin('x=1').then(() => {
+        const afterFiles = readdirSync(tmpdir()).filter((f) =>
+          f.startsWith('pythonShellSyntaxCheck'),
+        );
+        afterFiles.length.should.equal(beforeCount);
+        done();
+      });
+    });
+    it('should check syntax via stdin', function (done) {
+      PythonShell.checkSyntaxStdin('x=1').then(() => {
+        done();
+      });
+    });
+
+    it('should check multiline code via stdin', function (done) {
+      const code = `def hello():
+    print("world")
+hello()`;
+      PythonShell.checkSyntaxStdin(code).then(() => {
+        done();
+      });
+    });
+
+    it('should invalidate bad syntax via stdin', function (done) {
+      PythonShell.checkSyntaxStdin('x=').catch(() => {
+        done();
+      });
+    });
+
+    it('should invalidate syntax error in multiline code via stdin', function (done) {
+      const code = `def hello()
+    print("world")`;
+      PythonShell.checkSyntaxStdin(code).catch(() => {
+        done();
+      });
+    });
+
+    it('should use pythonOptions from defaultOptions', function (done) {
+      const originalOptions = PythonShell.defaultOptions;
+      PythonShell.defaultOptions = { pythonOptions: ['-B'] };
+
+      PythonShell.checkSyntaxStdin('x=1')
+        .then(() => {
+          PythonShell.defaultOptions = originalOptions;
+          done();
+        })
+        .catch((err) => {
+          PythonShell.defaultOptions = originalOptions;
+          done(err);
+        });
+    });
+  });
+
   // #158 these tests are failing on appveyor windows node 8/10 python 2/3
   // but they work locally on my windows machine .....
   // these methods are not that important so just commenting out tests untill someone fixes them