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node_modules/@rushstack/terminal/lib/DiscardStdoutTransform.js

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+"use strict";
+// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
+// See LICENSE in the project root for license information.
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.DiscardStdoutTransform = void 0;
+const ITerminalChunk_1 = require("./ITerminalChunk");
+const TerminalTransform_1 = require("./TerminalTransform");
+var State;
+(function (State) {
+    State[State["Okay"] = 0] = "Okay";
+    State[State["StderrFragment"] = 1] = "StderrFragment";
+    State[State["InsertLinefeed"] = 2] = "InsertLinefeed";
+})(State || (State = {}));
+/**
+ * `DiscardStdoutTransform` discards `stdout` chunks while fixing up malformed `stderr` lines.
+ *
+ * @remarks
+ * Suppose that a poorly behaved process produces output like this:
+ *
+ * ```ts
+ * process.stdout.write('Starting operation...\n');
+ * process.stderr.write('An error occurred');
+ * process.stdout.write('\nFinishing up\n');
+ * process.stderr.write('The process completed with errors\n');
+ * ```
+ *
+ * When `stdout` and `stderr` are combined on the console, the mistake in the output would not be noticeable:
+ * ```
+ * Starting operation...
+ * An error occurred
+ * Finishing up
+ * The process completed with errors
+ * ```
+ *
+ * However, if we discard `stdout`, then `stderr` is missing a newline:
+ * ```
+ * An error occurredThe process completed with errors
+ * ```
+ *
+ * Tooling scripts can introduce these sorts of problems via edge cases that are difficult to find and fix.
+ * `DiscardStdoutTransform` can discard the `stdout` stream and fix up `stderr`:
+ *
+ * ```
+ * An error occurred
+ * The process completed with errors
+ * ```
+ *
+ * @privateRemarks
+ * This class is experimental and marked as `@beta`.  The algorithm may need some fine-tuning, or there may
+ * be better solutions to this problem.
+ *
+ * @beta
+ */
+class DiscardStdoutTransform extends TerminalTransform_1.TerminalTransform {
+    constructor(options) {
+        super(options);
+        this._state = State.Okay;
+    }
+    onWriteChunk(chunk) {
+        if (chunk.text.indexOf('\r') >= 0) {
+            throw new Error('DiscardStdoutTransform expects chunks with normalized newlines');
+        }
+        if (chunk.kind === ITerminalChunk_1.TerminalChunkKind.Stdout) {
+            if (this._state === State.StderrFragment) {
+                if (chunk.text.indexOf('\n') >= 0) {
+                    this._state = State.InsertLinefeed;
+                }
+            }
+        }
+        else if (chunk.kind === ITerminalChunk_1.TerminalChunkKind.Stderr) {
+            let correctedText;
+            if (this._state === State.InsertLinefeed) {
+                correctedText = '\n' + chunk.text;
+            }
+            else {
+                correctedText = chunk.text;
+            }
+            this.destination.writeChunk({ kind: ITerminalChunk_1.TerminalChunkKind.Stderr, text: correctedText });
+            if (correctedText.length > 0) {
+                if (correctedText[correctedText.length - 1] === '\n') {
+                    this._state = State.Okay;
+                }
+                else {
+                    this._state = State.StderrFragment;
+                }
+            }
+        }
+        else {
+            this.destination.writeChunk(chunk);
+        }
+    }
+}
+exports.DiscardStdoutTransform = DiscardStdoutTransform;
+//# sourceMappingURL=DiscardStdoutTransform.js.map