Flask init_app() overwrites the previous handle without disposing it #20

Closed
#37
Closed
Flask init_app() overwrites the previous handle without disposing it#20
#37

Description

@AndresL230
AndresL230
opened on May 13, 2026

Flask init_app() overwrites the previous handle without disposing it

Severity: Medium
Affected repos:middleware-python
Component boundary: middleware-python Flask adapter

Symptom

The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.

Evidence

middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().

Impact

  • Tests that register the extension twice (common pattern in pytest) leak threads.
  • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.

Fix recommendation

definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)

Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."

Verification

  • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.

Related

Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.

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      , 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
       blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n 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;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

      Skip to content
      Flask init_app() overwrites the previous handle without disposing it #20
      Closed
      #37
      Closed
      Flask init_app() overwrites the previous handle without disposing it#20
      #37
      Description
      @AndresL230
      AndresL230
      opened on May 13, 2026
      Flask init_app() overwrites the previous handle without disposing it
      Severity: Medium
      Affected repos:middleware-python
      Component boundary: middleware-python Flask adapter
      Symptom
      The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
      Evidence
      middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
      Impact
      • Tests that register the extension twice (common pattern in pytest) leak threads.
      • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
      Fix recommendation
      definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
      Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
      Verification
      • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
      Related
      Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
      Metadata
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        No type
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          No milestone
          Relationships
          None yet
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          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

          Skip to content
          Flask init_app() overwrites the previous handle without disposing it #20
          Closed
          #37
          Closed
          Flask init_app() overwrites the previous handle without disposing it#20
          #37
          Description
          @AndresL230
          AndresL230
          opened on May 13, 2026
          Flask init_app() overwrites the previous handle without disposing it
          Severity: Medium
          Affected repos:middleware-python
          Component boundary: middleware-python Flask adapter
          Symptom
          The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
          Evidence
          middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
          Impact
          • Tests that register the extension twice (common pattern in pytest) leak threads.
          • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
          Fix recommendation
          definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
          Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
          Verification
          • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
          Related
          Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
          Metadata
          Metadata
          Assignees
          No one assigned
            Labels
            No labels
            No labels
            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)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              Flask init_app() overwrites the previous handle without disposing it #20
              Closed
              #37
              Closed
              Flask init_app() overwrites the previous handle without disposing it#20
              #37
              Description
              @AndresL230
              AndresL230
              opened on May 13, 2026
              Flask init_app() overwrites the previous handle without disposing it
              Severity: Medium
              Affected repos:middleware-python
              Component boundary: middleware-python Flask adapter
              Symptom
              The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
              Evidence
              middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
              Impact
              • Tests that register the extension twice (common pattern in pytest) leak threads.
              • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
              Fix recommendation
              definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
              Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
              Verification
              • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
              Related
              Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
              Metadata
              Metadata
              Assignees
              No one assigned
                Labels
                No labels
                No labels
                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)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

                  Skip to content
                  Flask init_app() overwrites the previous handle without disposing it #20
                  Closed
                  #37
                  Closed
                  Flask init_app() overwrites the previous handle without disposing it#20
                  #37
                  Description
                  @AndresL230
                  AndresL230
                  opened on May 13, 2026
                  Flask init_app() overwrites the previous handle without disposing it
                  Severity: Medium
                  Affected repos:middleware-python
                  Component boundary: middleware-python Flask adapter
                  Symptom
                  The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
                  Evidence
                  middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
                  Impact
                  • Tests that register the extension twice (common pattern in pytest) leak threads.
                  • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
                  Fix recommendation
                  definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
                  Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
                  Verification
                  • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
                  Related
                  Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
                  Metadata
                  Metadata
                  Assignees
                  No one assigned
                    Labels
                    No labels
                    No labels
                    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)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                      Skip to content
                      Flask init_app() overwrites the previous handle without disposing it #20
                      Closed
                      #37
                      Closed
                      Flask init_app() overwrites the previous handle without disposing it#20
                      #37
                      Description
                      @AndresL230
                      AndresL230
                      opened on May 13, 2026
                      Flask init_app() overwrites the previous handle without disposing it
                      Severity: Medium
                      Affected repos:middleware-python
                      Component boundary: middleware-python Flask adapter
                      Symptom
                      The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
                      Evidence
                      middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
                      Impact
                      • Tests that register the extension twice (common pattern in pytest) leak threads.
                      • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
                      Fix recommendation
                      definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
                      Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
                      Verification
                      • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
                      Related
                      Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
                      Metadata
                      Metadata
                      Assignees
                      No one assigned
                        Labels
                        No labels
                        No labels
                        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)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

                          Skip to content
                          Flask init_app() overwrites the previous handle without disposing it #20
                          Closed
                          #37
                          Closed
                          Flask init_app() overwrites the previous handle without disposing it#20
                          #37
                          Description
                          @AndresL230
                          AndresL230
                          opened on May 13, 2026
                          Flask init_app() overwrites the previous handle without disposing it
                          Severity: Medium
                          Affected repos:middleware-python
                          Component boundary: middleware-python Flask adapter
                          Symptom
                          The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
                          Evidence
                          middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
                          Impact
                          • Tests that register the extension twice (common pattern in pytest) leak threads.
                          • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
                          Fix recommendation
                          definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
                          Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
                          Verification
                          • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
                          Related
                          Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
                          Metadata
                          Metadata
                          Assignees
                          No one assigned
                            Labels
                            No labels
                            No labels
                            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)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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                              Flask init_app() overwrites the previous handle without disposing it #20
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                              #37
                              Closed
                              Flask init_app() overwrites the previous handle without disposing it#20
                              #37
                              Description
                              @AndresL230
                              AndresL230
                              opened on May 13, 2026
                              Flask init_app() overwrites the previous handle without disposing it
                              Severity: Medium
                              Affected repos:middleware-python
                              Component boundary: middleware-python Flask adapter
                              Symptom
                              The Flask extension's init_app() pattern allows the same ReCost() instance to bind to multiple Flask apps. Each call to init_app() invokes init(config) and stores the result in self._handle, overwriting the previous handle. The overwritten handle is never disposed: its flush timer keeps running, its transport thread keeps living, its interceptor patches stay installed.
                              Evidence
                              middleware-python/recost/frameworks/flask.py — init_app() does self._handle = init(config) with no prior self._handle.dispose().
                              Impact
                              • Tests that register the extension twice (common pattern in pytest) leak threads.
                              • Apps that re-init the extension on config reload leak timers and may emit interleaved telemetry for the same project.
                              Fix recommendation
                              definit_app(self, app: Flask, config: Optional[RecostConfig] =None, **kwargs: Any) ->None:
ifself._handleisnotNone:
self._handle.dispose()
self._handle=NoneifconfigisNone:
config=RecostConfig(**kwargs)
self._handle=init(config)
                              Document: "Calling init_app() again disposes the previous instance. Only one app is active per ReCost instance at a time."
                              Verification
                              • Test: call init_app(app1), then init_app(app2), assert threading.active_count() does not grow.
                              Related
                              Relates to existing #4 (Module-level state races: _handle, install/uninstall, init-vs-dispose). This is the specific Flask-adapter symptom of that broader concern.
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