From 4f7346e2ebcbf72181f147e38a7d94bcd443c08b Mon Sep 17 00:00:00 2001
From: Mike Donnalley <mdonnalley@salesforce.com>
Date: Tue, 2 Jan 2024 09:24:39 -0800
Subject: [PATCH] feat: add 'only' option to allowStdin (#900)

* feat: add 'only' option to allowStdin

* test: add more allowStdin tests
---
 src/interfaces/parser.ts  |  5 +++--
 src/parser/parse.ts       |  4 ++++
 test/parser/parse.test.ts | 44 ++++++++++++++++++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/src/interfaces/parser.ts b/src/interfaces/parser.ts
index d46616d7c..a1b00abb8 100644
--- a/src/interfaces/parser.ts
+++ b/src/interfaces/parser.ts
@@ -222,10 +222,11 @@ export type OptionFlagProps = FlagProps & {
    */
   delimiter?: ','
   /**
-   * Allow input value to be read from stdin.
+   * Allow input value to be read from stdin if the provided value is `-`.
+   * If set to `only`, the flag will only accept input from stdin.
    * Should only be used on one flag at a time.
    */
-  allowStdin?: boolean
+  allowStdin?: boolean | 'only'
 }
 
 export type FlagParserContext = Command & {token: FlagToken}
diff --git a/src/parser/parse.ts b/src/parser/parse.ts
index 14183efc2..4a60e3ddc 100644
--- a/src/parser/parse.ts
+++ b/src/parser/parse.ts
@@ -156,6 +156,10 @@ export class Parser<
           throw new CLIError(`Flag --${name} expects a value`)
         }
 
+        if (flag.allowStdin === 'only' && input !== '-') {
+          throw new CLIError(`Flag --${name} can only be read from stdin. The value must be "-".`)
+        }
+
         if (flag.allowStdin && input === '-') {
           const stdin = await readStdin()
           if (stdin) {
diff --git a/test/parser/parse.test.ts b/test/parser/parse.test.ts
index fb4d83afb..645044ae2 100644
--- a/test/parser/parse.test.ts
+++ b/test/parser/parse.test.ts
@@ -1872,7 +1872,7 @@ describe('allowStdin', () => {
     sandbox.restore()
   })
 
-  it('should read stdin as input for flag', async () => {
+  it('should read stdin as input for flag when value is "-"', async () => {
     sandbox.stub(parser, 'readStdin').returns(stdinPromise)
     const out = await parse(['--myflag', '-'], {
       flags: {
@@ -1883,4 +1883,46 @@ describe('allowStdin', () => {
     expect(out.flags.myflag).to.equals(stdinValue)
     expect(out.raw[0].input).to.equal('x')
   })
+
+  it('should not read stdin when value is not "-"', async () => {
+    sandbox.stub(parser, 'readStdin').returns(stdinPromise)
+    const out = await parse(['--myflag', 'foo'], {
+      flags: {
+        myflag: Flags.string({allowStdin: true}),
+      },
+    })
+
+    expect(out.flags.myflag).to.equals('foo')
+    expect(out.raw[0].input).to.equal('foo')
+  })
+
+  it('should read stdin as input for flag when allowStdin is "only" and when value is "-"', async () => {
+    sandbox.stub(parser, 'readStdin').returns(stdinPromise)
+    const out = await parse(['--myflag', '-'], {
+      flags: {
+        myflag: Flags.string({allowStdin: 'only'}),
+      },
+    })
+
+    expect(out.flags.myflag).to.equals(stdinValue)
+    expect(out.raw[0].input).to.equal('x')
+  })
+
+  it('should throw if allowStdin is "only" but value is not "-"', async () => {
+    sandbox.stub(parser, 'readStdin').returns(stdinPromise)
+    try {
+      await parse(['--myflag', 'INVALID'], {
+        flags: {
+          myflag: Flags.string({allowStdin: 'only'}),
+        },
+      })
+      expect.fail('Should have thrown an error')
+    } catch (error) {
+      if (error instanceof CLIError) {
+        expect(error.message).to.equal('Flag --myflag can only be read from stdin. The value must be "-".')
+      } else {
+        expect.fail('Should have thrown a CLIError')
+      }
+    }
+  })
 })