The bug
In certain scenarios, like the one described below, backspacing an open curly bracket will cause the game to freeze and crash.
The command used was so:
/setblock 2 69 -31 minecraft:lever{face:ceiling} replace
Under normal circumstances, this command has the incorrect notation and would return failure. The correct notation uses square brackets and an equals sign. However, the issue still remains in that placing the cursor in front of the open curly bracket and pressing backspace will immediately crash the console.
Although it would be easier to simply type the command correctly, it would be best to tie up any loose ends.
Crash report
17w47b\: [^crash-2017-11-23_23.36.52-client.txt]
Description: keyPressed event handler
java.lang.IllegalArgumentException: Non [a-z0-9/._-] character in path of location: minecraft:leverface:ceiling
at mp.<init>(SourceFile:31)
at mp.<init>(SourceFile:36)
at mp.a(SourceFile:121)
at cg.d(SourceFile:156)
at cg.a(SourceFile:69)
at cf.a(SourceFile:21)
at cf.parse(SourceFile:14)
at com.mojang.brigadier.tree.ArgumentCommandNode.parse(ArgumentCommandNode.java:55)
at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:169)
at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:191)
at com.mojang.brigadier.CommandDispatcher.parseNodes(CommandDispatcher.java:191)
at com.mojang.brigadier.CommandDispatcher.parse(CommandDispatcher.java:143)
at bpd.h(SourceFile:161)
at bpd.a(SourceFile:97)
at bpd$$Lambda$581/1727093989.accept(Unknown Source)
at bnm.a(SourceFile:145)
at bnm.b(SourceFile:194)
at bnm.keyPressed(SourceFile:326)
at bpd.keyPressed(SourceFile:134)
at bme.a(SourceFile:269)
at bme$$Lambda$578/1998450406.run(Unknown Source)
at bqb.a(SourceFile:428)
at bme.a(SourceFile:267)
at bme$$Lambda$110/2066315072.invoke(Unknown Source)
at org.lwjgl.glfw.GLFWKeyCallbackI.callback(GLFWKeyCallbackI.java:23)
at org.lwjgl.system.JNI.invokeV(Native Method)
at org.lwjgl.glfw.GLFW.glfwPollEvents(GLFW.java:2520)
at bmr.a(SourceFile:282)
at bmh.b(SourceFile:843)
at bmh.a(SourceFile:376)
at net.minecraft.client.main.Main.main(SourceFile:134)
This happened to me when I backspaced the second open square bracket in this command:
/execute store result entity @e[type=chicken,name="Harold",limit=1] Rotation[0]