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global.Promise replacement in Jest setup causing problems. #29303

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Closed
global.Promise replacement in Jest setup causing problems.#29303
Labels
Needs: Triage 🔍

Description

@chrisbobbe
chrisbobbe
opened on Jul 8, 2020

Hi! 👋

What is the purpose of replacing the global Promise in this line of jest/setup.js:

global.Promise=jest.requireActual('promise');

It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂

Description

'promise' refers to the NPM package with that name.

It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.

One interesting note on that issue, from a Jest maintainer, is this:

As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.

Might it be OK and appropriate to remove the line?

React Native version:

System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

Steps To Reproduce

Reproduction of the issue (and more discussion) at jestjs/jest#10221.

Expected Results

React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.

Metadata

Metadata

Assignees

No one assigned

    Labels

    Needs: Triage 🔍

    Type

    No type

    Projects

    No projects

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    No milestone

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    None yet

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    No branches or pull requests

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    , 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
     blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
    Skip to content
    global.Promise replacement in Jest setup causing problems. #29303
    Closed
    Closed
    global.Promise replacement in Jest setup causing problems.#29303
    Labels
    Needs: Triage 🔍
    Description
    @chrisbobbe
    chrisbobbe
    opened on Jul 8, 2020
    Hi! 👋
    What is the purpose of replacing the global Promise in this line of jest/setup.js:
    global.Promise=jest.requireActual('promise');
    It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
    Description
    'promise' refers to the NPM package with that name.
    It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
    One interesting note on that issue, from a Jest maintainer, is this:
    As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
    Might it be OK and appropriate to remove the line?
    React Native version:
    System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

    Steps To Reproduce
    Reproduction of the issue (and more discussion) at jestjs/jest#10221.
    Expected Results
    React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
    Metadata
    Metadata
    Assignees
    No one assigned
      Labels
      Needs: Triage 🔍
      Type
      No type
      Projects
      No projects
      Milestone
      No milestone
      Relationships
      None yet
      Development
      No branches or pull requests
      Issue actions
      
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
      Skip to content
      global.Promise replacement in Jest setup causing problems. #29303
      Closed
      Closed
      global.Promise replacement in Jest setup causing problems.#29303
      Labels
      Needs: Triage 🔍
      Description
      @chrisbobbe
      chrisbobbe
      opened on Jul 8, 2020
      Hi! 👋
      What is the purpose of replacing the global Promise in this line of jest/setup.js:
      global.Promise=jest.requireActual('promise');
      It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
      Description
      'promise' refers to the NPM package with that name.
      It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
      One interesting note on that issue, from a Jest maintainer, is this:
      As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
      Might it be OK and appropriate to remove the line?
      React Native version:
      System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

      Steps To Reproduce
      Reproduction of the issue (and more discussion) at jestjs/jest#10221.
      Expected Results
      React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
      Metadata
      Metadata
      Assignees
      No one assigned
        Labels
        Needs: Triage 🔍
        Type
        No type
        Projects
        No projects
        Milestone
        No milestone
        Relationships
        None yet
        Development
        No branches or pull requests
        Issue actions
        
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
        Skip to content
        global.Promise replacement in Jest setup causing problems. #29303
        Closed
        Closed
        global.Promise replacement in Jest setup causing problems.#29303
        Labels
        Needs: Triage 🔍
        Description
        @chrisbobbe
        chrisbobbe
        opened on Jul 8, 2020
        Hi! 👋
        What is the purpose of replacing the global Promise in this line of jest/setup.js:
        global.Promise=jest.requireActual('promise');
        It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
        Description
        'promise' refers to the NPM package with that name.
        It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
        One interesting note on that issue, from a Jest maintainer, is this:
        As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
        Might it be OK and appropriate to remove the line?
        React Native version:
        System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

        Steps To Reproduce
        Reproduction of the issue (and more discussion) at jestjs/jest#10221.
        Expected Results
        React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
        Metadata
        Metadata
        Assignees
        No one assigned
          Labels
          Needs: Triage 🔍
          Type
          No type
          Projects
          No projects
          Milestone
          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
          Skip to content
          global.Promise replacement in Jest setup causing problems. #29303
          Closed
          Closed
          global.Promise replacement in Jest setup causing problems.#29303
          Labels
          Needs: Triage 🔍
          Description
          @chrisbobbe
          chrisbobbe
          opened on Jul 8, 2020
          Hi! 👋
          What is the purpose of replacing the global Promise in this line of jest/setup.js:
          global.Promise=jest.requireActual('promise');
          It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
          Description
          'promise' refers to the NPM package with that name.
          It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
          One interesting note on that issue, from a Jest maintainer, is this:
          As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
          Might it be OK and appropriate to remove the line?
          React Native version:
          System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

          Steps To Reproduce
          Reproduction of the issue (and more discussion) at jestjs/jest#10221.
          Expected Results
          React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            Needs: Triage 🔍
            Type
            No type
            Projects
            No projects
            Milestone
            No milestone
            Relationships
            None yet
            Development
            No branches or pull requests
            Issue actions
            
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
            Skip to content
            global.Promise replacement in Jest setup causing problems. #29303
            Closed
            Closed
            global.Promise replacement in Jest setup causing problems.#29303
            Labels
            Needs: Triage 🔍
            Description
            @chrisbobbe
            chrisbobbe
            opened on Jul 8, 2020
            Hi! 👋
            What is the purpose of replacing the global Promise in this line of jest/setup.js:
            global.Promise=jest.requireActual('promise');
            It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
            Description
            'promise' refers to the NPM package with that name.
            It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
            One interesting note on that issue, from a Jest maintainer, is this:
            As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
            Might it be OK and appropriate to remove the line?
            React Native version:
            System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

            Steps To Reproduce
            Reproduction of the issue (and more discussion) at jestjs/jest#10221.
            Expected Results
            React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
            Metadata
            Metadata
            Assignees
            No one assigned
              Labels
              Needs: Triage 🔍
              Type
              No type
              Projects
              No projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
})();
`global.Promise` replacement in Jest setup causing problems. · Issue #29303 · react/react-native · GitHub
              Skip to content
              global.Promise replacement in Jest setup causing problems. #29303
              Closed
              Closed
              global.Promise replacement in Jest setup causing problems.#29303
              Labels
              Needs: Triage 🔍
              Description
              @chrisbobbe
              chrisbobbe
              opened on Jul 8, 2020
              Hi! 👋
              What is the purpose of replacing the global Promise in this line of jest/setup.js:
              global.Promise=jest.requireActual('promise');
              It looks like it was first introduced in 3ff3987 (quite a while ago) and has remained in a similar form since then. There's no explanation of this choice specifically (if I understand correctly), so I think if it must remain, it would be good to put a code comment there. 🙂
              Description
              'promise' refers to the NPM package with that name.
              It interferes with Jest when using their new "modern" implementation of fake timers (documented here), as I describe at jestjs/jest#10221.
              One interesting note on that issue, from a Jest maintainer, is this:
              As an aside, one should never replace global.Promise [...]. E.g. when using async-await you will always get the native Promise regardless of the value of global.Promise.
              Might it be OK and appropriate to remove the line?
              React Native version:
              System:
OS: macOS 10.15.5
CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
Memory: 4.84 GB / 16.00 GB
Shell: 3.2.57 - /bin/bash
Binaries:
Node: 10.20.1 - ~/.nvm/versions/node/v10.20.1/bin/node
Yarn: 1.22.4 - /usr/local/bin/yarn
npm: 6.14.4 - ~/.nvm/versions/node/v10.20.1/bin/npm
Watchman: 4.9.0 - /usr/local/bin/watchman
SDKs:
iOS SDK:
Platforms: iOS 13.5, DriverKit 19.0, macOS 10.15, tvOS 13.4, watchOS 6.2
Android SDK:
API Levels: 23, 25, 26, 27, 28, 29
Build Tools: 27.0.3, 28.0.3, 29.0.2
System Images: android-28 | Google Play Intel x86 Atom
IDEs:
Android Studio: 3.6 AI-192.7142.36.36.6241897
Xcode: 11.5/11E608c - /usr/bin/xcodebuild
npmPackages:
react: 16.8.6 => 16.8.6 react-native: 0.60.6 => 0.60.6

              Steps To Reproduce
              Reproduction of the issue (and more discussion) at jestjs/jest#10221.
              Expected Results
              React Native's Jest setup doesn't interfere with ordinary, well-documented ways of testing with Jest.
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